vvEPA

United StatesEnvironmental ProtectionAgency

Office of Research andDevelopmentWashington DC 20460

EPA.625/2-91/032February ,99

iRadon-resistantConstructionTechniques for NewResidential Construction

Technical Guidance

MechanicalBarriers

Planned MechanicalSystems

Sub-slabDepressurization

SiteEvaluation

EPA/625/2-91/032February 1991

Radon-resistant Construction Techniquesfor New Residential Construction

Technical Guidance

By

Mike ClarkinTerry Brennan

Camroden Associates, Inc.RD#1 Box 222 East Carter Road

Oriskany, NY 13424

EPA Contract No. 68-02-4287, Task 11

EPA Project Officer: Michael C. Osborne

/iir and Energy Engineering Research LaboratoryOffice of Environmental Engineering and Technology Demonstration

Office of Research and DevelopmentU.S. Environmental Protection Agency

Research Triangle Park, North Carolina 27711

Pnnted on Recycled Paper

Notice

The United States Environmental Protection Agency (EPA) strives to provideaccurate, complete, and useful information. However, neither EPA nor anyperson contributing to the preparation of this document makes any warranty,expressed or implied, with respect to the usefulness or effectiveness of anyinformation, method, or process disclosed in this material. Nor does EPAassume any liability for the use of, or for damages arising from, the use of anyinformation, methods, or process in this document

Mention of firms, trade names, or commercial products in this documentdoes not constitute endorsement or recommendation for use.

Table of Contents

PageList of Figures .................................................................................................................................vList of Tables.................................................................................-...............................-.............-.^Metric Conversions........................................................................................................................vi

Section 1Introduction .....................................................................................................................................1Section 2Overview .........................................................................................................................................32.1 Where Does Radon Come From and Why Is It a Problem? .....................................................32.2 How Radon Gets into a Home...................................................................................................32.3 Radon Control in New Construction .........................................................................................42.3.1 Sub-slab Depressurization/Pressurization Systems................................................................52.3.2 Mechanical Barriers ...............................................................................................................62.3.3 The Site ..................................................................................................................................72.3.4 Planned Mechanical Systems.................................................................................................92.4 Recommendations.....................................................................................................................92.4.1 Sub-slab Depressurization Systems .......................................................................................92.4.2 Mechanical Barriers .............................................................................................................10Section 3Soil Depressurization ....................................................................................................................13Introduction................................................................................................................................... 133.1 Sub-slab Depressurii^ition Overview...................................................................................... 133.2 Sub-slab Depressurization Systems ........................................................................................ 133.2.1 Overall Design Considerations - Active and Passive Systems ............................................133.2.2 Sub-slab Preparation ............................................................................................................153.2.3 Preparation of the Slab ......................................................................................................... 163.2.4 Active Sub-slab Depressurization System Materials and Installation Details ..................... 163.2.5 Passive Sub-slab Depressurization System Components and Installation Details............... 163.3 A Crawlspace Post-construction Alternative .......................................................................... 17Section 4Mechanical Barriers ......................................................................................................................19Introduction ...................................................................................................................................194.2 Foundation Materials............................................................................................................... 194.3 Common Masonry Wall Details and Their Impact on Radon Resistance...............................204.3.1 Masonry Walls with Termite Caps, Solid Blocks, and Filled Block Tops ..........................20

4.3.2 Masonry Walls with Weep Holes.........................................................................................214.3.3 Stemwalls in Slab-on-grade Houses.....................................................................................214.3.4 Foundation Walls in Crawlspace Houses............................................................................214.4 Floors in Basements, Slabs on Grade, and Crawlspaces.........................................................214.4.1 Crack Prevention ..................................................................................................................214.4.2 Joints.....................................................................................................................................224.4.3 Penetrations..........................................................................................................................234.5 Crawlspaces.............................................................................................................................244.6 Coatings...................................................................................................................................254.6.1 Introduction ..........................................................................................................................254.6.2 Dampproofing/Waterproofing to Achieve a Radon Barrier.................................................264.7 Membranes.........................................................................................................—..................264.7.1 Introduction ..........................................................................................................................264.7.2 Types of Membranes Available ...........................................................................................274.8 Mechanical Barriers Applied to the Soil .................................................................................284.9 Drainage Boards for Soil Gas and Radon Control ..................................................................284.10 Summary of Recommendations for Mechanical Barriers................................................... .4.10.1 Rules of Thumb for Foundation Walls...............................................................................^84.10.2 Rules of Thumb for Slab and Sub-slab Barriers ................................................................28

Section 5Site Evaluation ..............................................................................................................................31Introduction ...................................................................................................................................315.2 Radon in the Soil .....................................................................................................................315.2.1 Attempted Correlations Between Indoor Radon and Measurements Made at Sites .............315.2.2 Indexes Using Permeability and Soil Radon Concentrations...............................................325.2.3 Variations in Spatial and Temporal Soil Gas Concentrations..............................................335.3 Radon Observed in Nearby Houses ........................................................................................345.4 Airborne Measurements ..........................................................................................................345.5 Radon in Water........................................................................................................................345.6 Radon in Building Materials ...................................................................................................

Section 6Planned Ventilation.......................................................................................................................35Introduction ...................................................................................................................................356.2 Interdependence of Mechanical Systems and Climate............................................................356.3 Guidelines for Planning the Mechanical System ....................................................................356.4 Two Illustrations .....................................................................................................................366.5 Conclusions.............................................................................................................................37

References....................................................................................................................................39Appendix ACurrent Radon-resistant New Construction Research Effons...................................................... 41Appendix BOther Radon-resistant New Construction Guidelines ..................................................................43

IV

List of Figures

FigurePage

2.1 Radon Decay Chart ..............................................................................................................42.2 Percentage of Radon Contributions by Source from 15 Homes..........................................52.3 Typical Radon Entry Routes in Basement Foundations ......................................................62.4 Typical Crawlspace Foundation Entry Routes ....................................................................72.5 Typical Radon Entry Routes in Slab-on-grade Construction ..............................................82.6 Major Radon-resistant New Construction Topics ...............................................................92.7 Sub-slab Depressurization Theory..................................................................................... 102.8 Radon-resistant Barrier Theory ........................................................................................ 113.1 Negative Pressure Sources in a Typical Home.................................................................. 143.2 Theory of Operation of a Sub-slab Depressurization System ........................................... 153.3 Typical Sub-slab Depressurization System ....................................................................... 174.1 Sealing a French Drain ......................................................................................................234.2 Sealing a Sump Hole .........................................................................................................254.3 Summary of Mechanical Barrier Approach for Basement Foundations ..........................284.4 Summary of Mechanical Barrier Approach for Slab-on-grade Foundations ....................294.5 Summary of Mechanical Barrier Approach for Crawlspace Foundations ........................29

List of Tables

Table Page3.1 Summary of Radon Concentrations in EPA New Construction Projects ......................... 134.3 Results Using Vented Crawlspace Technique ..................................................................255.1 Florida Survey Soil Radon and Corresponding Indoor Radon Concentrations ................325.2 Swedish Soil Risk Classification Scheme and Building Restrictions...............................325.3 Geometric Means for Soil Gas Radon-222, Soil Radium-226, Permeability,

RIN, and Indoor Radon-222 .............................................................................................325.4 Indoor Radon and Soil Radon Measurements in Colorado and Michigan .......................33Al Current EPA/AEERL Radon-resistant New Construction Projects..................................41A2 Preliminary Results from Current EPA Research Projects...............................................42

Metric Conversions

Readers more familiar with the metric system may use the following to conven to that system.

Nonmetric Multiplied bv Yields Metriccfm 0.000472 m'sft 0.305 mft1 0.0929 m*in. 0.0254 mIb 0.454 kgIb/ft 1.488 kg/mmil 0.0000254 mpsi 6.895 kPapCi/L 37 Bq/m3

VI

Section 1Introduction

Growing concern about the risks posed by indoor radon,a naturally occurring radioactive gas found in varying amountsin nearly all houses, has underscored the need for dependableradon-resistant residential construction techniques, in responseto this public health exposure, the U.S. Environmental Pro-tection Agency (EPA) has developed and demonstrated avariety of methods that have been used to reduce radonlevels in existing houses. Many of these methods could beapplied during construction, involve less labor and financialinvestments, and provide greater homeowner satisfaction andsafety than would a radon-reduction technique installed afterthe home is built and occupied.

This manual is designed to provide homeowners andbuilders with an understanding of operating principles andinstallation details of radon-resistant new home construction.To meet these needs, the manual is divided into four pans.The first pan contains the Introduction, which you are nowreading. The second part containing Section 2 is the Over-view, which covers techniques being studied or used in thecontrol of radon in new homes. Underlying operating prin-ciples, materials, and installation are discussed in Section 2.The level of detail is aimed at developing an understandingof basics, not background or details. The overview is quicklyand easily read. The third pan, Sections 3-6, contains techni-cal information which takes the same material to a greater

depth, and covers additional specific construction detailsThis part contains far more technical information than ihcintroduction and overview, and will require more effort 10read and assimilate. The fourth part, the Appendices, containsbackground information on the contents of the first threeparts.

The intent of this manual is not to rate similar productsmade by different manufacturers, or to provide a stock radon-resistant package. This manual should provide a basic un-derstanding of the types of products and systems that arcavailable and being used. In this way, the reader will be ableto select radon-resistant products and systems that wi l l hemost applicable to a particular situation.

It should be understood that some of the techniquesmentioned in this manual have NOT yet been fully dcrrnMi-strated in new home construction. These techniques arcdiscussed because they have a sound theoretical potential foreffectively precluding radon entry into a home. As researchcontinues, and experience in the use of radon-resistant newconstruction techniques grows, it is expected that some ofthese theories will prove to be transferable to the homcbuilder\list of radon-resistant construction options. The soil ventila-tion techniques described HAVE been extensively tested inexisting homes and show good potential for application mnew construction and are, therefore, recommended.

Section 2Overview

Two areas are addressed in the Overview.

Radon Entry - How radon enters a buildingRadon Control - What can be done to lowerindoor radon levels.

2.1 Where Does Radon come from and Why isit a Problem?

Radon gas is the result of the radioactive decay ofradium-226, an element that can be found in varying concen-trations throughout many soils and bedrock. Figure 2.1 showsthe scries of elements that begin with uranium-238, and, afterundergoing a scries of radioactive decays, lead eventually tolcad-210. At the time radium decays to become radon gas,energy is released. Of all the elements and isotopes illus-trated in Figure 2.1, radon is the only one which behaves likea gas and can easily slip through the small spaces betweenbits of soil. While many of the isotopes in the uranium-238decay scries exist for a long lime before they decay, radondocs not remain radon for very long. It has a half-life of 3.8days. If 1 Ib* of radon were put in a jar, 3.8 days later only I/2-lb of radon would be left; the other 1/2-lb would havedecayed into the short lived decay products polonium, bismuthand lead. After another 3.8 days only 1/4-lb of radon wouldbe left in the jar. The radon decay products shown inside thebuilding have even shorter half lives than radon, and decaywithin a few hours to the relatively stable isotope lead-210.It is this rapid release of energy thai causes radon and radondecay products to pose such a significant health risk.

If radon and radon decay products arc present in the air,they will be inhaled. Because the decay products are notgases, they will slick to lung tissue or larger airborne particleswhich later lodge in the lung. The energy given off as theseisotopes decay, can strike the cells in the lung, damagetissue, and may eventually develop into lung cancer. Theamouni of risk depends on how long a person is exposed tohow high a concentration of radon and radon decay products.Estimates of the number of lung cancer deaths attributable toradon and radon decay products ranges from approximately5.000 to 20.000 deaths per year in the Uniicd States.

For simplicity, in the remainder of this manual, radonand radon decay products will be collectively referred to asradon, except where the distinction is required.

For the reader's convenience, nonmetric units are used in this document.Readers more familiar with the metric system may use the factors in thefront matter to convert to that system.

22 How Radon Gets into a HomeA house will contain radon if the following four condi-

tions exist:

1) a source of radium exists to produce radon2) a pathway exists from the radium to the house3) a driving force exists to move the radon 10 the

house4) an opening in the house exists to permit radon

to enter.If one of these conditions does not exist, then the house

will not have a radon problem. An estimated 10 to 20% ofthe existing homes in the United States have annual averageradon concentrations above 4 picocuries per liter of air (pCi/L). This may seem like a small percentage of problemhomes until one considers that, of the million or so U.S.houses built each year, 100,000 to 200,000 homes will likelyhave radon concentrations higher than 4 pCi/L.

The most common way radon enters a home is whenlower indoor air pressure draws air from the soil, bedrock ordrainage system into the house. If there is radon in the soilgas, it will also be drawn in. Just as gravity will make waterflow from a high elevation to a lower elevation, pressuredifferences will make radon-laden air move from an area ofhigher pressure to an area of lower pressure. For a variety ofreasons, illustrated at length in the Technical Informationsection, most buildings tend to maintain an indoor air pressurelower than outdoor air pressure. If cracks and holes in thefoundation are open to the soil, radon will be drawn indoors.Radon movement by pressure differences is called pressuredriven transport

Radon can also enter buildings when there are no pressuredifferences. Place a drop of food coloring in a glass of waterand eventually the coloring will spread out (diffuse) andcolor the water - - even without stirring. Radon will do thesame thing - - spread from an area of higher concentration toan area of lower concentration until the concentrations arcequal. Radon movement in this way is called diffusiondriven transport

A less common entry mechanism is the outgassing ofradon from well water. A well supplied by groundwater thatis in contact with a radium-bearing formation can transportihe dissolved radon into ihe home. Al the ume of thiswriting, it is estimated that the health risks associated withbreathing radon gas released from the water are 10 limeshigher than the risks associated with ingesting water contain-ing radon.

214Polonium0.00016seconds

214Bismuth

19.7minutes

218Polonium

3minutes

214Lead27

minutes238

Uranium4.47 billion

years

Figure 2.1. Radon Decay Chart Radon has a long enough half-life to allow H to move from some distance away fromthe house through the soil into the building. Although some of the radon in the building will be removedwith ventilation air, much will be trapped In the building and decay before H Is removed.

Radon can also emanate from the building materialsthemselves. The extent of the use of radium contaminatedbuilding materials is unknown but is generally believed to besmall.

Figure 2.2 illustrates the percentages of contribution byeach type of radon entry made to a specific group of studyhouses in the Pacific NW (Se89). Any one house can varysignificantly from these figures. However, on a nationalbasis this is an indication of the relative importance of eachof the contributors.

Figures 2.3, 2.4, and 2.5 illustrate typical radon entryroutes found in basement, crawlspace, and slab-on-fjadeconstruction.

2.3 Radon Control in New ConstructionLike most other indoor air contaminants, radon can be

controlled by keeping it out of the house, or reducing theconcentration by mixing it with fresh air after it has already

entered. The following approaches have been tried or sug-gested:

• Prevent EntryMake provisions for a sub-slab depressurizationor pressurizaiion system during constructionInstall mechanical barriers to block soil-gas en-tryAvoid risky sites

• Planned Mechanical SystemsSupply fresh air to reduce radon by dilutionControl pressure relationships to reduce soil-airentry.

Figure 2.6 illustrates the four major topics to be consid-ered in this manual - Site Evaluation, Mechanical Barriers,Sub-slab Depressurization and Planned Mechanical Systems.All four of these topics are covered in the Overview and

Flgur* 2.2. P*ro*ntag« o; Radon Contribution* by Sourc* from 15 Home*.

Technical Information sections. This illustration will alsoserve as an index to help you use this manual. The pages inthe Overview and Technical Information sections where theyare covered are listed beneath each topic.23.1 Sub-Slab Depressuwation/Pressurization

Systems.One of the most frequently used radon reduction tech-

niques in existing homes is a sub-slab depressurization system.Typical installation costs for a system in existing homesrange from $1,000 to $2,000. If the same system is installedor at least planned for, and roughed in during construction,the cost is much lower, so a prudent builder who is erecting aradon-resistant home should include features that will allowfor the easy installation of such a system.

A sub-slab depressurization system creates a low pres-sure zone beneath the slab using a pipe system to exhaust the

soil-gas from beneath the foundation. This prevents soil-gasfrom entering the building by reversing the airflow direction.Air will flow from the house into the soil, effectively sealingall the remaining foundation cracks and holes. For a simpleview of the operating principle of a sub-slab depressurizationsystem, refer to Figure 2.7

A sub-slab pressurization system creates a high pressurezone beneath the slab. Although this does not reverse thedirection of the airflow ( the air from the system will stillflow into the home through cracks and holes), it does dilutethe radon concentrations beneath the slab and may keepradon that is being produced in the site from getting to thefoundation. In a number of existing houses it has been foundthat this technique performed better than sub-slab depressur-rzation. In buildings where pressurization works best thereare a few common factors. One is the presence of soil orbedrock that allows air to move very easily through it. So

fl1 =

1 =

1 =

\

— Open tops of hollowcore masonry blocks

__ Diffuses throughinterior of wall Dampproofing or _

waterproofing

Cracks in foundation-1 ' • ' • — • • wa||s

Loose form ties ——

Floor drains Cracks in floor

Open pipepenetrations ^^^and joints ^^

-/V

•ana*

• MM

Figure 2.3. Typical Radon Entry Routea In Baawnmt Foundation*.

easily, in fact, that it is difficult to establish a low piessu-efield by exhausting 100 cfm or so of air from beneath theslab. It is this feature that limits the performance of soildepressurization systems. The other factors that seem im-portant are either a relatively low concentration of radon inthe soil-gas, or a remote location for the source radium, withradon transported some distance from the house through thevery permeable soil. It is thought that a positive pressurecreated by blowing low radon concentration air under theslab dilutes the soil-gas near the foundation, and diverts soil-gas originating farther away. Pressurization has been suc-cessfully used in buildings built in coarse gravel, shatteredshales, and limestones. This technique has been used inexisting homes to reduce radon concentrations; however,there has been no major research effort to verify the actualeffectiveness of pressurization. Other factors to considerwhen installing a pressurization system are the effect theintroduction of, in some climates, below freezing or highhumidity air will have on the concrete floor slab, aid theeffort that must be made to ensure that the air intake does notbecome blocked by foreign matter.

Sub-slab depressurizalion/pressurization systems arcdiscussed in detail in Section 3.

23.2 Mechanical BarriersKnowing that the greatest contributor to indoor radon

concentrations is air from the soil entering the building throughthe foundation, it was thought that a good place to beginbuilding a radon-resistant home is to make the foundation asradon-resistant as possible. Figure 2.8 illustrates the principleof a radon barrier. Many materials (concrete, polymericcoatings and plastic films) are outstanding air barriers andretard the transfer of radon gas by a large factor. In practice,the difficulties that arise when using barrier techniques arenumerous. Failure to seal a single opening may negate theentire effort. Barriers may degrade with time or may bedamaged during installation. The use of barrier techniquesas a stand-alone system is not recommended, but it is rec-ommended that some amount of effort be made to l imi t theentry of radon through the foundation. This can be done byusing :

Figure 2.4 Typical Crawlspace Foundation Entry Routes.

foundation mmcrials themselves, sealing cracks,joints and penetrations

• foundation coatings, normally used fordampproofing

• membranes surrounding the foundation.This section will briefly discuss foundation design and

materials. Methods used to -control cracking, treating thecracks that do form, and ways to seal planned foundationpenetrations will be reviewed. The material presented in thismanual can be easily adapted to buildings with basements,crawlspaces, or slab-on-grade foundations.

It should be pointed out that attempts to control radon bymaking a gaslight barrier around the foundation have notbeen completely effective. It is likely they have done somegood, but many newly constructed buildings that relied onbarrier's as the only radon reduction technique have elevatedlevels of indoor radori. It is not known, however, what theindoor radon concentrations would have been if the barriershad not been installed. This is covered in more detail later inthe manual.

2J.3 The SiteThe question most often asked by homebuilders is can

one determine if radon-resistant construction techniques shouldbe applied to a given site?

A simple test that could identify problem sites would bevery helpful. At present, there are no simple, reliable meth-ods for doing this. The reasons for this are covered in theTechnical Information section. In the absence of a simplesite screening test, guidance can be sought in the growingbody of information developed at regional, state and locallevels. Many researchers, public agencies and privatehomcowncrs are making soil, bedrock and indoor radonmeasurements. From these data a picture of the extent of theproblem is emerging. While noi yet possible to be certainabout a given site, some idea of where the problem areas arehas been developed. At a recent meeting of several leadingmitigation contractors, the general consensus was to installradon-resistant techniques rather than spend extra lime andmoney performing the number of pre-construcuon tests iiwould lake 10 confidently evaluaie the site. However, a

Penetrations andlOints

Figure 2.5. Typical Radon Enlry Routes in Slab-on-grade Construction

group of testing contractors may decide just the opposite.Although no definitive methods for predicting possible in-door radon concentrations based upon pre-construction soilmeasurements exist, it is clear that a building being erectedon a site that is known to contain high concentrations ofradon should have radon-resistant construction techniquesapplied. Another concern when evaluating the site potentialfor supplying radon to the soon-to-be-constructed home isthe permeability of the soil. A highly permeable soil allowseasy movement of soil gases; therefore, radon can move agreater distance from the source to the building than in atighter, less permeable soil. This can also allow soil-gasesthat contain lower concentrations of radon to enter the liomein greater quantities, which can produce elevated ind< orconcentrations. Swedish Authorities suggest that a buildingsite with soil radon concentrations greater than 1350 pCi/Lor with a highly permeable soil should use radon resistantconstruction techniques (Ak86).

We do not recommend the avoidance of building sitesthat are suspected to contain strong radon sources. We do,however, strongly recommend that the homes built on thosesites be designed and built with radon-resistant constructiontechniques.

Water from wells has been found to be a major sour:e ofradon in some homes in the United States. Radon willoutgas from the rocks into the groundwater. When the wateris exposed to the atmosphere, some of the radon is relezised.

Builders should be aware that wells can be a potentialproblem. The only way to ensure that a well is rot apotential radon source is to have the water tested after thewell is drilled. It is not adequate to make a decision based

upon tests made in wells in the same area or even on adjoin-ing building sites. A recent research project disclosed twohomes with water radon concentrations of over 400,000 pCi/L, while the well used at a house between the two hadwaterbome radon concentrations of less than 1000 pCi/L(Ni89). It should be understood that, when consideringwaterbome radon, the concentrations that concern us aremuch higher than when we are considering radon in the air.As a rule of thumb, between 8,000 and 10,000 pCi/L ofradon in the water will contribute 1 pCi/L of radon into theair. There is no standard or guideline for the amount ofradon allowable in the water as yet, but a guideline is exptto be set soon. Contact your regional EPA office for moreinformation on pending guidelines.

If radon is present in the water, the current state oftechnology offers two possible solutions. Water that isaerated will release the radon it carries. Several manufactur-ers have systems designed to aerate the water and vent theradon outdoors. An alternative system filters the waterthrough granulated activated carbon which removes the radonfrom the water. There are several manufacturers of granulatedactivated carbon water filters. It should be noted here that athigh radon levels (greater than 5,000 pCi/L) the buildup ofradon decay products in the charcoal can produce a signifi-cant level of gamma radiation. Although this can be allevi-ated by proper shielding, disposal of the charcoal filter mediacan be a problem.

A site suspected to contain a waterbome source of radonshould not be avoided solely on the basis of the existence ofradon. Methods can be utilized to alleviate any problem thatmay arise from waterbome radon.

Mechanical BarriersOverview Page 16Technical InformationPage 37

Sub-slab DepressurizationOverview Page 14Technical Information Page 24

MechanicalPlanned_____SystemsOverview Page 19Technical InformationPage 83

Site EvaluationOverview Page 17Technical Information Page 70

Figure 2.6. Major Radon-resistant New Construdlon Topics.

23.4 Planned Mechanical SystemsThe entry of soil gas into buildings is the result of a

complex interaction between the building shell, the mechani-cal system, and the climate. Important climatic variables arethe wind velocity, i. door/outdoor temperature differences,rainfall, and atmospheric pressure changes. Indoor radonconcentrations can be reduced by planning the mechanicalsystem so that fresh air dilutes the radon that has entered thebuilding, and by controlling interior air pressures to reducesoil gas entry. This approach has not been extensively testedin the EPA Demonstration Projects in existing homes. It alsorequires a great deal of insight into the dynamics of buildingoperation for a given climate. These issues are discussed atmore length in the Technical Information section. If thismethod is considered, the following guidance can be used:

• Be sure that combustion appliance performanceis not impacted.

• Supply fresh air in accordance with ASHRAErequirements.

Consult ASHRAE (ASHRAE85) ventilation requirementsand the National Fire Protection Association (NFPA1). As asystem is designed, consider the use of:

Power vented combustion devices or combustiondevices that use outside air.

• Fresh air supply ventilation systems (heatrecovery or non-heat recovery).

2.4 RecommendationsThe following sections contain recommended radon-re-

sistant construction techniques that a builder may wish toincorporate into the home. It should be understood that theseare recommendations only and should not be construed asguidelines or regulations. The recommendations are basedupon (he best available information gathered from numerousresearch projects.2.4.1 Sub-Slab Depressurization Systems

To facilitate the use of soil depressurization, it is sug-gested that a permeable layer of material be placed beneaththe slab, all the major foundation penetrations be sealed anda passive stack be run from the permeable layer up throughthe roof like a plumbing vent. Appropriate materials for thepermeable layer are 3/8 to 1-1/2 in. diameter stone pebbles,or manufactured drainage products (perforated plastic pipe ordrain boards). A passive stack is much easier to add while

"~ Radon gas in soil

Radium in soil

Flgur* 2.7. Sub-slab D«pr**«uriz*tlon Theory.

building the house, and is easily power vented later if re-quired. There is evidence that, while not foolproof, a propertydesigned passive venting system can sometimes have someimpact on indoor radon levels.

2.4.2 Mechanical BarriersBelow-grade walls may be constructed of poured con-

crete, masonry blocks, or other materials such as all-weatherwood or stone. This manual discusses details for use inpoured concrete and masonry foundations because these arethe most common materials used for new construction. Re-cently, trade associations such as the American PlywoodAssociation and the National Forest Products Associationhave issued publications on designing radon-resistant penna-nent wood foundations. Information on these types of foun-dations can be found by contacting the appropriate tradeassociation (NFoPA88).

The following is a list of recommendations that builderscan use to utilize the foundation as a mechanical barrier toradon entry.

Foundation walls and floor slabs are often constructed ofpoured concrete. Plastic shrinkage, and therefore cracking, isa natural function of the drying process of concrete. Manyfactors, such as the water/cement/aggregaie ratio, humidity,and temperature, influence the amount of cracking that oc:ursin a poured concrete foundation. Cracking may be minimizedby:

• Proper preparation, mixture, and curing ofconcrete(ACI302.1R-80, ACI332R-84)

• Ferrous reinforcing (rebar rods and woven wiremeshes)

• Use of concrete additives to change thecharacteristics of concrete

• Water reducing plasticizers, fiber-reinforcedcements (ACI212.1R-81).

To help prevent cracking in masonry walls, or minimizethe effects of cracks that do develop:

• Using correct thickness of unit for depth of soil(NCMA71)

• Using ferrous reinforcing (comers, joints, topcourse) (NCMA68)

• Coating interior and exterior of wall withdampproofing.

Cracks and joints in concrete and concrete block can besealed using caulks. Polyurethane caulks have many of theproperties required for durable closure of cracks in concrete.These features are:

• Durability• Abrasion resistance

Flexibility• Adhesion• Simple surface preparation

Acceptable health and safety impacts.Typical points that should be sealed with caulks are :• Plumbing penetrations (soil pipes and water

lines as minimum)

10

Radium in soil

Figure 2.8. Radon-resistant Barrier Theory.

Radon gas in soil

• Perimeter slab/wall crack and expansion joints(tool crack or use "zip" off expansion jointmaterial.

The open tops of concrete block walls are openingsthat should be sealed. This can be done by installing a rowof solid blocks, lintel blocks or termite cap blocks at the topof the wall.

Drainage details that leave openings through the founda-tion should be avoided or modified. Sump holes and frenchdrains are widely used examples of this type of detailing. Itis best to avoid them if possible, by using alternate drainagesystems. When the.se design details are unavoidable, a littlethought can allow the use of these details and still keep radonfrom entering the home. The Technical Information sectionwill discuss these designs in greater detail.

In many areas of the country, some type of dampproofingor waterproofing treatment is required by code.

The application of dampproofing and waterproofing ma-terials on the exterior, interior, or both sides of the foundationthat can serve as a radon resistant barrier is recommended tohelp control radon entry. It must be understood that acoating applied to a foundation intended to resist the flow ofradon into the building is in addition to the normal water-proofing/dampproofing requirements.

Coatings are applied to the outside or inside of thefoundation, creating a radon- resistant barrier between thesource and the inside of the home. They come in a widevariety of materials including paint-like products that can bebrushed on the interior of the foundation, tar-like materialsthat are applied to the outside, and cementitioas materialsthat can be brushed or troweled on. They cannot be appliedto the underside of the concrete floor slab for obvious reasons,so must be applied to the inside surface of the slab. Theeffective life of an interior coating can be greatly diminishedby damage; therefore, care must be taken to provide protec-tion to the material used.

Membrane barriers are applied to the exterior of thefoundation and also beneath the floor slab during construc-tion. Materials used for the membrane barriers range fromco-extruded poly olefm to pdyvinyl chloride to foil sheetswith many other materials in between. All membrane barri-ers must have the edges sealed to prevent radon from mi-grating around the edges and back into the building.

It is recommended that, as a minimum, a membrane beplaced beneath the slab, and all foundation penetrations tothe soil be sealed or otherwise dealt with in a manner whichwill prevent the entry of radon into the home.

11

Section 3Soil Depressurization

IntroductionThe next four sections contain details and references for

those wishing a deeper understanding of radon-resistant con-struction issues. The four major topics:

• Sub-slab Depressurization• Mechanical Barriers• Site Evaluation

Planned Mechanical Systemsare used to organize this portion of the manual.

In theory, the application of radon barriers should beadequate to avoid elevated radon levels in houses. In prac-tice, however, a backup radon mitigation system has beenfound essential for maintaining indoor radon concentrationsbelow 4 pCi/L in most homes studied. In recent radon-resistant residential construction projects conducted by EPAand/or private builders, several of the homes designed to beradon-resistant have contained radon concentrations above 4pCi/L. In each of those houses a backup system consistingof an active (fan assisted), or passive (wind and stack effectassisted), sub-slab depressurization system was installed atthe time of construction. When mechanical barriers failed toadequately control radon, the soil depressurization methodswere made operational.3.1 Sub-Slab Depressurization Overview

Of the study homes mentioned in the previous section,some passive systems seemed sufficient to lower the radonconcentrations, while in all cases, active systems resulted insignificantly lower concentrations. However, some of thoseprojects are on-going and longer term testing may show thatsome of the active systems will fail to maintain concentrationsbelow the guideline for the long term. Table 3.1 summarizesthe findings of these particular projects. See Appendix A formore information on the data contained in this table.Table 3.1 Summary of Radon Concentrations In EPA New

Construction Project*.Soil Depressurization

Project * House* Barrier Only Passive ActivepCI/L pCi/L pCI/L

EPA-VA1EPA-NY1EPA-VA2EPA-PA1

101521

1451581.313.4

60139<17.0

<128<11.1

The most common way radon enters a home is when airpressure differences move soil gases containing radon throughthe spaces between soil particles to the foundation of thehome. Just as gravity will make water flow from a higher

area to a lower area, pressure differences will make radonladen soil gases move from an area of higher pressure to anarea of lower pressure. Most buildings tend to maintainthemselves at an air pressure lower than the surrounding soil.This characteristic is due to weather driven parameters suchas indoor/outdoor temperature differences and wind. Theuse of exhaust fans and combustion devices in a home wil lalso create a negative pressure in the home. If cracks andholes in the foundation are open to the surrounding soil,radon will be drawn into the building. Figure 3.1 illustratesthe principle of pressure transported radon and also showssome of the things that produce the differences in pressure.Refer to the section on planned ventilation for more infor-mation on pressure differences.

3.2 Sub-Slab Depressurization SystemsAs previously mentioned, the air pressure in most homes

is less than the air pressure in the surrounding soil. Thedifference in air pressures is what draws radon into thehome. A sub-slab depressurization system alters the pressurebeneath the concrete slab, making the sub-slab pressure lessthan the indoor pressure. It is the altered air pressures thaikeep radon from entering the home.

Figure 3.2 shows the theory of operation, a simple sys-tem layout, and the components of a sub-slab deprcssuriza-tion system.

Careful attention to detail when in the design stage of asub-slab depressurization system will help ensure the easyinstallation of a system if it is found to be required. Theproper details are given in the following sub-sections, begin-ning at the sub-slab area and progressing upward to theexhaust32.1 Overall Design Considerations— Active and

Passive SystemsWhen designing an active or passive system, many de-

sign considerations are common to the two systems. Forexample, some provision for removal of condensation thatforms in the exhaust pipe will be required. Routing of thepipes from the basement to the roof must be considered whenthe house is being designed. Placement of the exhaust isextremely important.

Removal of condensation is an important consideration.Water collecting in an elbow or other low point of the systemcan effectively block the pipe, and reduce or disable thesystem. Builders should strive to design a pipe system thatwill allow condensation to run back through the pipe to thesub-slab aggregate. This can be accomplished by ensuring

13

Figure 3.1. Negative Pre**ur« Source* In • Typical Home.

that the pipe run is vertical the entire distance from thebasement to the exhaust A completely vertical pipe run withno bends or elbows will also provide a pipe system withlower static pressure losses which enhances the effectivenessof both active and passive systems. If elbows or a low pointis incorporated in the design, a condensaie pump can be usedto drain the water away. The use of condensaie pumps willincrease the cost of the system both in materials and labor, sothe ideal situation is to design a system that does not requirepumps.

Pipe routing should be considered when the home isbeing designed. This will ensure that there is an area reservedfor the exhaust pipe and preclude any possibility of having tobuild the system with numerous elbows and long horizontal

pipe runs. Ideally, the pipes should be run through aninterior wall of the home or up through closets.

The exhaust should be located above the highest ridgeline. Some builders prefer to exhaust their systems out anattached garage roof, rather than through the main roof. Thistype design does require at least one short horizontal run, andwill not seriously impact the effectiveness of an active system.When choosing the exhaust point, avoid the reentry ofradon-laden soil-gas into the home through open windowsand doors. Do not exhaust the soil-gas in an outdoor occupiedarea such as a porch or patio. Locating the exhaust close to achimney that could backdraft and draw the exhausted soil-gas back into (he home should also be avoided. For a gooddiscussion on the theory of exhaust design, see the 1985

14

Fan

Medium pressure zone

Low pressure zone

High pressure zone

Figure 3.2. Theory of Operation of a Sub-Slab Oepretsurlzatlon System.

edition of the ASHRAE Fundamentals Handbook, Chapter14 (ASHRAE85).32.2 Sub-Slab Preparation

Figure 3.2 illustrated that a low pressure area beingdeveloped beneath the slab will draw the radon out of thesoil, up the pipe, and exhaust the gas outdoors. If the sub-slab material consists of tightly packed soil or contains largerocks, the pressure field may not extend to all areas of thesoil surrounding the foundation, and allow radon to enter thehome where ihe pressure field does not exist. One way ofensuring the proper extension of the pressure field is toinstall media beneath the slab prior to the pour that willallow the easy movement of the air, thus helping to extendthe pressure field.

In areas where it is available, crushed gravel is aninexpensive material to use. Sub-slab gravel provides adrainage bed for moisture and a stable, level surface forpouring the slab. The material preferred for radon reduction

is crushed aggregate with a minimum of 80% of the aggre-gate at least 3/4 in. in diameter. This stone should have afree void space above 40 %. One standard specification ofthis type of gravel is D.O.T. # 2 gravel. A minimum of 4 in.of aggregate should be placed under the enure slab. Caremust be taken to avoid introducing fine dirt particles duringand after placement of the aggregate.

In areas where gravel is not readily available, drainagemats designed for soil stabilization may be used. The use ofthese drainage mats may not be cost effective in areas wheregravel is available, but where gravel must be shipped in fromlong distances, drainage mats can be cost effective.

Some builders prefer laying perforated PVC piping inthe gravel before the slab is poured, and connecting theperforated pipe to the exhaust pipe of the system. The use ofperforated pipe may not be necessary in active systems butprobably will assist a passive system.

15

Membranes beneath the slab help to keep a continuousradon bamcr in the event of slab cracking. For more infor-mation on this detail see the discussion on membrane barriers.

The use of fooling drains for water control can affect thedistribution of the pressure field. Interior footing drainssometimes terminate in a sump hole. If this is the case andthe sump hole is not sealed airtight, the possibility exists forair to be drawn into the sump by the sub-slab system andweaken the pressure field. Make sure all sumps are sealedairtight. Sometimes interior footing drains extend out beneaththe footing and run to daylight, as shown in the section onmechanical barriers. If this is the case, provision must bemade to make the ends of the drain airtight whi le stillallowing water to drain. Reverse-flow valves are ideal forthis application.

To summarize, any opening or connection that allowsthe deprcssurization system to draw air from anywhere butbeneath the slab is detrimental to its effectiveness and mustbe avoided.32.3 Preparation of the Slab

A thorough discussion of slabs is included in the sectionon foundation materials as mechanical barriers and should bereferred to. However, when installing a soil depressurizationsystem, it is more important to seal the large openings thatwould defeat extension of a low pressure field than \: is toseal every small crack. This is because the airflow throughsmall cracks from the building into the soil will effectivelyseal them against soil gas entry.32.4 Active Sub-Slab Depressurization System

Materials and Installation DetailsAs can be seen on Figure 3.3, active sub-slab deprissur-

izaiion systems consist chiefly of a pipe system and a fan.There are several other components that should be includedin a good system, but are not necessary to make the systemreduce radon concentrations.

Most builders use 4 in. schedule 20 PVC pipe. Othersizes can be used but 4 in. PVC is readily available and iscommonly used by builders for other purposes. Fans madefor use in sub-slab systems are available in a variety of sizesfrom many vendors. The fans normally used are rated in arange of 90 to 150 cfm at no static pressure. Manufacturersof fans used for radon reduction are fairly quick to improvetheir products on advice from the people who are using theirproducts. When the radon industry first started, many of thefans leaked at seams and joints, and required disassembly ofthe fan to seal those openings. Most manufacturers nowsupply fans that do not leak, but builders should be awarethat this problem did exist and may still exist in some fans.

Additional materials and components that are normallyincluded in a system satisfy safety needs, system performanceindications, and common sense.

Service switches should be placed within view of the fanto ensure that the system will not be activated while mainte-nance is in progress.

Systems should be clearly marked as a radon reductiondevice to ensure that future owners of the building do not

remove or defeat the system. An operation manual describ-ing the system and its purpose should be made available.

Some type of device should be included tn the system toadvise ihe owners on system performance. These devicesmay be simple pressure gauges that tap into the pipe andmeasure and display the pressure in the exhaust pipe. Avisual check of the gauge will alert the homeowner topossible system malfunctions. Electronic pressure sensingdevices that illuminate a warning light or sound an audiblealarm when a pressure drop occurs arc also used but costmore than a simple gauge indicator. It is advisable lu use adevice that warns of a pressure change rather than somethingthat warns that the fan is not running because there areseveral things that can stop a system from operating effectivelythat do not effect the fan.

Rain caps at the end of the pipe are intended to keep rainfrom entering the system. Builders use various cap designsfor this purpose. The use of rain caps can cause a loss of airflow in a system, which may lessen the effectiveness of thesystem. It is advisable to use a rain cap that is designed insuch a way as to not seriously impede airflow. For moreinformation on rain caps and stack design, see the ASK £1985 Fundamentals Handbook, Chapter 14 (ASHRAE8$T

Attention to detail during the installation process willhelp ensure the proper operation and long life of the system.Starting at the floor slab, seal the void between the pipe andthe floor slab with a non-shrink grout or a flexible, highlyadhesive sealant. Place a sticker or other labeling device onthe pipe identifying the pipe as belonging to a radon reductionsystem. Ideally a label should be placed at regular intervalsalong the enure pipe run. A visual system performancemonitoring device should be placed in an area that is oftenvisited and in plain view of the homeowner. Audible alarmscan be placed in any area, as long as the homeowner can hearthem. It is a good idea to place alarm sensors in easilyaccessible areas because they sometimes need adjusting. Runthe pipe as straight as possible to the attic to ensure properdraining of condensation. The fan should always be locatedin a non-living area as close to the exhaust as possible,is extremely important because a leak in the fan or imrfepiping above the fan will blow the radon back out of thepipe. If the fan is placed in the basement, and a pipe leakoccurs above the fan, radon laden air will be introduced intothe living area, and can cause radon levels to build to veryhigh concentrations. Most builders connect the fans to thepipe system with rubber sewage pipe connectors. This allowsfor the easy removal and replacement of the fan if thatshould become necessary. Always install a service switch insight of the fan. Run the pipe through the roof and flashwell. If desired, cap the pipe with a rain cap.JJ.5 Passive Sub-Slab Depressurization System

Components and Installation DetailsA passive system is much the same as an active system

with the exception of the fan. A passive system relies onlyon stack and wind effects to produce the pressure field. Ascan be seen on Table 3.1, passive systems do not alwaysreduce radon concentrations to acceptable levels, but carefuldesign and installation may improve the effectiveness of apassive system.

16

Flashing

Rain cap

Centrifugal fanServiceswitch

Sewage linecouplers

Alarm system

Identificationlabel Caulk joints

and ^seams >^

Flgurt 3.3 Typical Sub-slab D*pr»s*urlzatlon Syalam.

4 in. crushedgravel D.O.T.# 2

It is probably beneficial to a passive system to lay anetwork of perforated drainage pipes in the gravel bed beneaththe slab prior to the pour. The use of horizontal pipe runsand elbows in a passive system may greatly lessen the effec-tiveness to the system and should be avoided. Some buildersuse 6 in. PVC in a passive system to help lessen the pressuredrop.

3.3 A Crawlspace Post-construction AlternativeDue to difficulties often encountered in sealing subfloors

and insulating pipes in crawlspace houses, which rarely havea poured floor slab, another radon-resistant alternative thatcan be applied after construction should be considered. Thismitigation technique is a variation of the successful sub-slab

depressurization methods used in basements. Polyethylenesheeting is often used as a moisture barrier applied directlyover the soil in crawlspaces. The polyethylene sheeting canbe used as a gaslight barrier that forms a small-volumeplenum above the soil where radon collects. A fan can beinstalled to pull the collected soil gas from under the sheetingand exhaust it outside the house.

The wide-width polyethylene sheets should be set directlyon the earth in a way that produces at least 1-ft overlaps.Some Held applications have included a bead of caulking toseal between sheets of polyethylene. A better seal has beenachieved by using an aerosol spray. A good seal is obtainedby spraying both surfaces of the polyethylene, allowing timefor them to get tacky, and pushing the two pieces of poly-

17

eihylene together. In locations where the soil surface is piers or walls. Many others have not been successful with-exceptionally hard and smooth or the crawlspace is "cry out sealing. When this technique is used, a complete sealinglarge, a drainage material can be placed under the sheeting to job is recommended for greatest protection. Application ofimprove airflow. If a large number of support piers exist or this technique may not be appropriate in crawlspaces thatif the suction point is located close to support piers, the receive heavy traffic,polyethylene sheeting should be sealed to the piers withcaulking and wood strips. The plastic sheeting may also be Some builders Prefer to concrete the floor of crawlspacessealed to the foundation walls to reduce air leaks. Some *hen sile ** desif" conditions permit getting the mix intoretrofit applications of this crawlspace radon mitigadon «•* crawlspace. If a crawlspace has a concrete slab, fortechnique have worked well without attempting to seal the radon-resistant construction the crawlspace should be treatedsheets of polyethylene together or sealing the polyethylene to sirmlar «° a basement with the advantage of greater ventila-

tion potential.

18

Section 4Mechanical Barriers

IntroductionThis manual has presented four topics concerning radon-

resistant construction issues. Discussed in this manual aretechniques to:

1) prevent radon entry by using a sub-slabdepressurization system

2) prevent radon entry by using mechanical barriers3) reduce radon and radon entry with planned

mechanical systems4) determine the potential for a radon problem by

evaluating the site.This section addresses the mechanical barrier approach.

Section 3 addresses building in a sub-slab depressurizationsystem. Section 5 discusses site evaluation. Section 6addresses a ventilation system planned to supply outdoor au-to the house, and reduce the pressure differentials that drivesoil-gas into the building.

Theoretically, a gaslight barrier could be placed betweenthe soil and foundation to eliminate radon entry from thesoil. Like many other building details, it is much easier todraw such a detail than to actually install it. Many materialsform effective retarders to gas transport. The problem iseffectively sealing cracks, joints and penetrations. As any-one who has tried to build an airtight house can tell you, it isnot as easy as it seems.

The types of mechanical barriers that have been tried orsuggested (jr radon control, fit into one of the followingcategories:

• foundation materials themselves• coatings

membranes• possibility of a "site" barrier.Ongoing EPA research on radon-resistant new construc-

tion has encountered numerous difficulties in making agaslight mechanical barrier effective enough to confidentlykeep indoor radon levels below 4 pCi/L. The types ofproblems encountered included quality control on the job;incomplete communication between researchers, contractorsand subcontractors; reluctance of builders to change drainagedetailing; and the smallness of the radon atoms.

The first problems on the list are not specific to radoncontrol but are encountered on nearly every construction job.In spite of quality control and communication problems, andthe understandable wariness builders show when asked to

build something in a different way, the residential construc-tion industry has responded to new techniques, materials andpublic demands. The average house being built today is verydifferent than a home built 10 years ago. If a product ormethod can be demonstrated to reliably keep radon out wi th-out presenting significant problems with cost, scheduling orinstallation, many builders would learn to use it The majordifficulty faced by mechanical barrier approaches is the thor-oughness that seems to be required to ensure that no radonproblem will occur.

In 1988 and 1989, EPA projects studied newly con-structed houses which incorporated mechanical barriers andprovisions for active and passive sub-slab dcprcssun/.ation todetermine ihe effectiveness of each approach. Preliminaryresults from these five studies found that, when there was asource of radon beneath the houses, the mechanical barrierswere not adequate to ensure basement levels below 4 pCi/L.However, there is no way to judge how high the radonconcentrations in these buildings would have been had themechanical barriers not been employed. These data shouldnot be used as evidence that the barriers used (or that me-chanical barriers in general) do not reduce radon levels in-doors. In fact there are good reasons to employ barriers toenhance the performance and reduce the energy penalty ofsoil depressurization techniques.

When trying to make a barrier to soil gas entry, theroutes of concern in new construction are the same as thosethat have previously been identified for existing houses.These entry routes are covered in Part 2, the Overview.Houses that are combinations of the above substructuresoften provide additional entry routes at the interface betweenthe two substructures. The following subsections address thetypes of mechanical barriers (foundation materials, coatingsarid membranes), the potential radon entry routes associatedwith common foundation detailing, and suggestions for de-tails that reduce the risk of elevated indoor radon. Whenpossible, these alternatives include barriers that can be usedto block radon entry while continuing to use traditionalconstruction methods. Depending on current local or regionalbuilding practices, some of ihe suggestions may require sig-nificantly different construction methods.

4.2 Foundation MaterialsThe materials used to construct a foundation can often

be used as an effective barrier to the entry of radon laden soilgas. Below-grade walls may be constructed of poured con-crete, masonry, or other materials such as pressure treatedwood or stone. The materials covered in this section, pouredconcrete and masonry block, are the most common for now

19

construction. Details for radon protection in permanent woodfoundations can be found in a National Forest ProductsAssociation publication entitled "Radon Reduction in WoodFloor and Wood Foundation Systems" (NFoPASS).

In residential buildings, foundation walls made of pouredconcrete are generally constructed to a compressive strengthof 2,500 to 3,000 psi. The forms are held together withmetal ties that penetrate the wall. A poured concrete wall isa good bamer to radon transport. The major weaknesses inthis regard are cracks, joints and penetrations, tt is theseopenings in the'walls that allow soil gas to enter the buildingwithout actually having to diffuse through the concrete. It isrecommended that concrete walls be built in compliance withguidelines established by the American Concrete Institute(ACI332R-84). Such concepts as cover mix, reinforcing,slump, temperature, vibration and a variety of other factorshelp to keep the foundation from cracking.

Residential foundation walls built of concrete masonryunits may have open cores, filled cores or cores closed at thetop course. Masonry walls are frequently coated with anexterior layer of cementitious material, referred to as "parg-ing," for water control. This coating is usually coved at thebottom of the wall to make a good exterior seal at the jointbetween the footing and the block wall. Uncoated blockwalls can range in porosity depending on the type of aggre-gate used. Uncoated blocks are neither an effective waternor radon barrier. It is recommended that concrete blockwalls be built according to guidelines issued by the NationalConcrete Masonry Association (NCMA72). Their publica-tions cover thickness of block, reinforcing, pilaster location,control joints, sequencing and other issues that preventcracking or foundation failure.

There are geographic areas throughout the U.S. in whichthe majority of foundation walls are poured concrete andother areas where masonry walls predominate. Poured con-crete walls arc generally available only in areas where con-tractors have the in-house expertise to build them and eitherrent or have invested in reusable forms. In areas where bothtypes of construction are found, the costs of each seemcompetitive.

There are building codes that dictate dampproofing orwaterproofing treatment for both type foundations. Thetreatments can also inhibit gas movement through the wall.Concrete blocks are much more porous than poured concrete,although the parge or waterproofing coats moderate the dif-ference. Recent laboratory tests have confirmed that uncoatedconcrete masonry walls allow substantial airflow, but thatthere is a great deal of variation in the porosity of blocks, duemainly to the use of different aggregates by the block manu-facturer. Block walls can allow substantial soil gas circula-tion in the cores of unfilled blocks, providing an area sourceof radon. Various measures are available to alleviate thisproblem, including exterior (or interior) gas barrier membranesand solid or filled block tops.

Although it is clear that concrete blocks are more porousthan poured concrete, some studies reveal no strong correla-tions concluding that a home built with a concrete blockfoundation is more likely to have a radon problem than one

built with a poured concrete foundation. A New Jet^cv -4u d>(Ru88) found mean radon concentrations in 5X1 basementswith poured concrete walls of 6.3 pCi/L ~ U 1 r< and iha t ihemean concentration in 3408 basements bu i l t *uh concreteblock walls was 5.7 pCi/L r l l .1%. There is no suust icaldifference between the two means. A survey conducted inConnecticut (Si90) in a smaller sample population revealed ageometric mean radon concentration of approximately I ~pCi/L in 755 homes with poured concrete foundations. Thesame study revealed a mean concentration of approximately2.0 pCi/L in 129 homes with block foundations. Theamount of error in the two means is not known at the t ime ofthis writing; however, it is suspected to be significantly highenough to show no statistical significance between the tuomeans. It is one more example of a variable that would seemto have an effect on indoor radon concentrations not meetingthose expectatioru. The expected effect is lost in the com-plex interaction of the far more important factors that affectradon source strength and transport. It is interesting to notethat the 639 stone foundations tested had mean basementradon concentrations of 6.2 pCi/L ± 10.1%, virtually identicalto the other two types of foundation walls.

4.3 Common Masonry Wall Details and Then^Impact on Radon Resistance

4J.I Masonry Walls with Termite Caps, SolidBlocks, and Filled Block Tops

Builders may construct a foundation wall with solid,filled, or sealed block tops for several reasons includingtermite-proofing, energy conservation, distribution of weightof the structure and radon-resistance. The National ConcreteMasonry Association (NCMA72) recommends that a solid orgrouted top course be installed to distrioute the loads ofjoists and beams. Some building codes require solid tops toblock hidden termite entry. In spite of this, the block tops inmany residences are left open except at anchor points. Houseshave been observed in which block tops were generallysealed, but cores were left unsealed at access doors tocrawlspaces, around ash pit doors and other openings. Seal-ing hollow cores at or near their tops can prevent soilfrom entering the basement, but more importantly mi^mmake the building easier to mitigate in the event that it haselevated radon. Sealing the bottom course might prevent airbeneath the slab from entering the block wall, but if the wallcores are used as part of a water control method it may notbe possible.

It is recommended for potential radon control to sealopen blocks at the time of construction.

Block tops have been successfully sealed using :• mortar mixed with plastic binder to fill the top

cores (quality control and shrinkage can beproblems)

• "Termite caps" - cored blocks with a 2-in. thicksolid cap as the top coursesolid or lintel blocks to seal one of the topcourses.

When solid blocks or termite caps are used, anchor boltsmust be placed in the joints between the blocks. Lintel

20

blocks and grouted top courses allow for more flexible place-ment.43.2 Masonry Walls with Weep Holes

Weep holes are used to drain water from the block coresinto the sub-slab area when surface: waterproofing barriersfail. Such a connection between the exterior and interiorsub-slab area is an obvious channel for radon entry, allowingsoil gas to pass from the sub-slab to the interior of the blockwall. Openings from the sub-slab into the block wall wouldalso make it more difficult to apply active sub-slab depres-surization at a later date. If the block tops are sealed and theinterior of the block wall is sealed, then weep holes would bemuch less of a problem as radon entry points or as barriers tosub-slab depressurization.

The National Concrete Masonry Association (NCMA)issues technical notes to provide contractors with guidance inconstruction practice. The NCMA-TEK 43, Concrete Ma-sonry Foundation Walls (NCMA72), provides illustratedcross-sections of foundation walls showing weep holes throughthe footing. These run from the exterior of the wall to thesub-slab area, connecting an exterior drainage system to aninterior drainage system. This system does not directly drainthe block wall, but the combination of dampproofing andexterior drainage should make it unnecessary.

Contractors often create weep holes in the bottom courseof block rather than buying prefabricated weep block. Somemasons open holes in both shells of the block; others openthe block cores to the interior but leave the exterior shellintact. Some builders prefer weep holes as an alternative toexterior drainage, while other builders reportedly use weepblocks in lieu of backfilling with granular material, althoughsuch backfilling is recommended or required in most areas.The actual need for weep holes in properly designed andconstructed masonry walls is questionable. Moreover, asolid block installed as the bottom course of a foundationwall is recommended to keep radon from seeping into blockcores around the footing. The NCMA-TEK 160A, RadonSafe Basement Construction (NCMA87), shows no weepholes in walls or footings but offers no prediction of theconsequences of eliminating them. A potential concern isthat even properly applied waterproofing materials may failover time.

It has been suggested that it might be possible to retainthe weep hole while venting the upper blocks above grade toallow soil gas to escape. This idea has not yet been tested,and would need to be combined with an interior barrier suchas paint. In general, weep holes should be avoided and, ifdrainage problems are expected, an exterior drainage systemshould be installed.

It is recommended that, if weep holes are used, carebe taken that they do not present a radon entry path or abarrier to later sub-slab depressurization. At this time thebest approaches appear to be either avoiding weep holes bycarefully planning and installing a drainage system that wouldprevent water from entering the block walls or sealing theblock tops and interior of the block wall.

4J.3 Stemwalls in Slab-on-Grade HousesStemwalls, also called frost walls, are below grade foun-

dations that support the load of the above grade *alls andthereby the roof. There is usually a footing beneath them atsome depth below the frost line. The major radon relatedissue fottihejje walls is the geometry of the slab/stemwalljoint This will be covered in the section on floors. ItStemwalls are constructed of concrete blocks then the blocktops should be sealed. See Sections 5.3.1 and 5.3.2.

4.3.4 Foundation Walls in -Crawlspace HousesFoundation walls in ventilated crawlspaces are substan-

tially different than walls in basements and unventilatedcrawlspaces. In basements and slab-on-grade buildings it isclear that barriers should be applied between the soil and thefoundation or be the foundation itself. With ventilatedcrawlspaces there are two locations that present themselvesfor the application of barriers. First, as in the other, barrierscan be placed between the soil and foundation. Secondly, abarrier effort can be made between the crawlspace and theupstairs living area at the floor deck. The second option willbe treated in Section 4.5. If the first option, making a barrierbetween the soil and the crawlspace, is selected, then thebasement wall details that apply to sealing open blocktopsand preventing the foundation from cracking also apply tothe crawlspace walls.

4.4 Floors in Basements, Slabs on Grade, andCrawlspaces

Concrete slabs are the only floors considered for thissub-section. As already pointed out in the beginning ofSection 3.2, poured concrete is a good rctarder for radon gasand soil gas. The major problems will be cracks, joints andpenetrations. The focus of this sub-section will be on crackprevention and sealing joints and penetrations. A good dealof this material applies to both poured concrete and masonrywalls.4.4.1 Crack Prevention

Plastic shrinkage cracking of concrete is a natural func-tion of the drying process. Many factors come into play asconcrete cures, including water content, cement content, at-mospheric humidity, temperature, humidity, air movementover the slab surface and aggregate >ntent. The preparationof the sub-slab area is also important. Reinforcement can beused to reduce shrinkage cracking. It has not been tradition-ally mandatory in residential floor slabs. Residential build-ers typically become concerned about shrinkage crackingand/or slab reinforcement when they are working in areaswith unstable soils or when they need to ensure slab integrityunder specific finished floor systems (ceramic tile, for ex-ample).

There are many ways to minimize slab cracking, al-though it probably cannot be eliminated entirely. TheAmerican Concrete Institute (ACT) publishes a number ofdocuments outlining standard practice for building concreteand concrete masonry structures. A number of these apply tocrack prevention. Specifically the reader is referred to

21

ACI302.1R-80 Guide for Concrete Floor and Slab Construc-tion, and ACI332R-84 Guide to Residential Cast in Pl,iceConcrete. The following discussion describes a number oftreatments, some of which are familiar to the commercial/institutional/industrial construction area but uncommon tothe residential marketplace.

Reinforcement with ferrous metals: The use of metal re-inforcement embedded in the slab increases its strength.Woven wire mesh is the most common material for residen-tial applications. For slabs on grade, the Council of Ameri-can Building Officials (CAB086) One and Two FamilyDwelling Code recommends 6 x 6 in. - W2.9 x W2.9 wovenwire mesh. To help control cracking it has been suggestedthat this is appropriate for a basement slab as well.

Rcbar (also called rcrod) is most commonly used forfootings or garage slabs and would not generally be usedthroughout a basement slab. A No. 4 rebar (1/2 in. bar) ams0.668 Ib/ft. It would probably be installed in a garage slab12 in. on center, leaving 3 in. at each end and running in bothdirections.

Concrete additives: A number of additives can be usedto change the characteristics of concrete. The AmericanConcrete Institute (ACI) discusses these additives in itstechnical guides. A discussion of the various fibers used toreinforce concrete, is tilled State of the Art Report on FiberReinforced Concrete (ACI544).

Water-reducing admixtures: Also known as plasticizers,these admixtures reduce the amount of water used in theconcrete. This reduces shrinkage and cracking while in-creasing the workability of the concrete. One example of aplasticizcr is WRDA-19, by Grace Construction Products,which is labeled "an aqueous solution of a modified naph-thalene sulfonatc, containing no added chloride." Chloridesare frequently added to concrete as antifreezes, but variouscodes l imit the chloride content of concrete because of itscorrosive effect on ferrous metals and its reducing effects onconcrete strength. American ATCON's report to the FloridaPhosphate Institute (Sc87) recommends the use of a plasticberto reduce the likelihood of water being added on site toproduce more workable concrete. See ACI212.1R-81, Ad-mixtures for Concrete.

Fiber-reinforced concrete: Various fiber additives areavailable that can reinforce poured concrete and reduce plas-tic shrinkage cracking. Fiber reinforcing has the advantageover woven wire mesh in that the fibers are homogeneouslydistributed throughout the slab thickness. The type of fiberused is important because studies have shown that the alka-line environment of Portland cement destroys some of tiefibers that are sold for this purpose. Polyester fibers andglass fibers have been noted by ACI as being vulnerable inan alkaline environment. Some companies apply a surfacetreatment to fibers to protect them from damage by alkalinity(glass fibers so treated are known in the trade as "AR fi-bers"), but the ends of the fibers are exposed when they arechopped up during the manufacturing process, and they candecay from the ends inward. The polypropylene materialused in some fiber products is chemically stable in an alkalineenvironment. The much higher modulus of elasticity of

glass fibers compared to organic fibers may be an advantagefor the glass since it more nearly matches the modulus ofelasticity of concrete. The comments above apply 10 fiberadditives used in surface-bonding mortars as *el! as thoseused in poured concrete slabs. See ACI212.1R-81, Admix-tures for Concrete.

Curing: Proper curing is critical to the strength anddurability of poured concrete. Many avenues are available toensure a good cure, ranging from watenng the slab to cover-ing it with wet sand, wet sawdust, or a waterproof f i lm [e.g.,waterproof paper, BurleneTM (bur lap/polyethylene)] orcoating it with a curing compound. Penetrating epoxy sealerapplied to the slab while it is still wet can act as a curingagent and slab sirengihener. Polyurethane sealants arc appliedafter the slab is dry, because moisture would l i f t them off theslab. There are a number of other liquid membranes andemulsions, including a number of solvents which requiresubstantial ventilation as they dry.

Use of higher strength concrete: Typical residentialconcrete slab construction requires a 28-day compressivpstrength of only 2,500 to 3,000 psi. Concrete can be rnsstronger by reducing the water/cement ratio. If the water/cement ratio is kept at 0.5 or less, the minimum 28-daycompressive strength will increase to 3800 psi. Moreover, ifthe ratio is reduced to 0.45, the compressive strength in-creases to 4300 psi. To achieve compressive strengths ofabove 3500 psi, the slump cannot exceed 3 in. The com-pressive strength and the slump of the concrete are no moreimportant, however, than the placability of the concrete orthe finishability of the surface. Unfortunately, placabilityand finishability are not easily measured quantities like slumpand compressive strength, and often do not receive sufficientemphasis.4.4.2 Joints

French Drains and Floor/Wall Cracks: The French drain(also called a channel drain or floating slab) is a constructionfeature that appears to provoke strong reaction from its defenders and detractors alike. French drains are only a co ___cern in basement foundations. This slab detail is a standardfeature in new houses in parts of the country as varied asNew York and Colorado, but in other places it is virtuallyunknown. French drains are used in areas with expansivesoils, such as parts of Colorado, to protect the slab fromdamage if the wall moves. In central New York state, themain function of the French drain is to drain away waterwhich may seep down the walls. One national builder hasdiscontinued and now prohibits the use of French drains inhouses because of the potential for radon problems. Thisbuilder states that French drains also have been found tosignificantly increase indoor moisture levels.

Various treatments can be used to seal French drainsagainst gas entry. Some of those treatments have crack-spanning capability in case of structural movement. Frenchdrains can be sealed airtight and still preserve their waterdrainage function by caulking the channel to a level belowthe top of the slab and sloping the trough toward the sump.This assumes that the sump lid is inset below the surface ofthe slab and that a water-trapped drain in the sump lid drains

22

Backer rod Self leveling urethane caulkU

A

Sealed sump withdrainage channel

Water still free to move from blockcore to sub-slab drainage layer

Figure 4.1 Sealing • French Drain.

water into the sump,treatment

Figure 4.1 shows a French drain

It is recommended that French drains be avoided ifpossible because of the difficulty in sealing them at the timeof construction and the expense and difficulty of sealingthem after construction.

Perimeter Crack: The perimeter crack is located be-tween the edge of the floor slab and the foundation wall.This applies to slabs in basements, crawlspaces and slab-on-grade foundations. As a cold joint, this perimeter crack isalways a potential radon entry point. Contractors buildingradon-resistant houses may deliberately create a significantfloor/wall crack so that it will be easy to work with and seal.A perimeter expansion joint is made of a closed-cell, flexiblefoam strip. The expansion joint is presliced so that the top I/2 in. an be pulled off to leave room for caulk. Anotherapproach is to tool the floor/wall joint with an edging tooland seal it with caulk. Particular attention should be paid tosealing this crack in slab-on-grade houses because the joint isoften inaccessible after the house walls are raised.

Control Joints: When large areas of slab are poured,some cracks are unavoidable. There will be cold jointsbecause the slab was poured in small sections to avoidcracks, or the slab will crack because the pours were toolarge. To direct the inevitable cracking that will occur ineither case, a control joint can be made by grooving thesurface of the slab. The groove should be large enough toseal with caulk. Cold joints can make use of the sameexpansion joint materials that have a "zip off top that wasdescribed for the slab edge crack.4.4 J Penetrations

Every house has some minimum of penetrations throughthe slab or foundation walls. The ones always present are :

• water pipe entry

• sewer pipe exitCommon additional penetrations are:• floor drains• sump holes• air conditioner condensaie drains.Openings around water pipe entries and sewer exits that

pass through concrete can be easily sealed using caulks.Many builders use plastic sleeves to protect metal pipes fromcorrosion when they pass through concrete. In this case aneffort can be made to leave a space around the pipe that canbe sealed with caulk or backer rod and caulk. The sametechniques can be used for pipes passing through blockwalls.

Depending on the details of a. floor drain, a great deal ofsoil gas can enter through large openings to the drainaj:matrix. This is true not only of slop drains that are simplyholes through slabs into the sub-slab area, but also of othertypes of drains. Even water trapped drains with water in thetraps can allow radon an entry passage where the dish shapedbottom of the drain seats into the drain pipe. It is recom-mended that floor drains connect to pipe that drains to day-light using solid PVC pipe glued at the joints, or that watertrapped drains or mechanical traps be installed that do nothave unsealed joints on the room side of the water trap.

Sump holes are usually a collection point for the drain-age system. Almost by definition this is a terrifically goodradon collection system. It must have access to large areasof soil beneath the foundation so it is easier for water to runinto the sump than to penetrate the foundation. It is better ifthere is no open sump at all. A sub-slab drainage system thatcan drain by gravity to a daylight opening serves the samepurpose as a sump hole but offers no fewer radon entryroutes. If this is not possible then the sump hole must besealed (a code item in some places to keep children from

23

playing in them). Sumps can be sealed airtight and stillfunction as a water collection and removal system by routingthe interior and/or exterior drainage pipes or layer into thesump. The sump hole is then sealed with a corrosion resis-Lar.t lid that is recessed a few inches to create a shallowsump. The lid is fitted with a water trapped drain so waterthat happens across the floor will end up in the sump.Lastly, a low profile sump pump is installed to eject anywater collected in the sump through a check valve to ap-proved disposal. This detail is illustrated in Figure 4.2.

Air conditioner condensate lines are sometimes instilledso that they penetrate the slab to dispose of the water in thesub-slab area. Even when water is trapped, this can be aproblem because the traps often dry up during the heatingseason. At this point they become radon entry routes. It isrecommended that air conditioning condensate lines run to adram that wil l not dry out or that a condensate pump beinstalled that collects the condensate and disposes of it througha water trap. Often a washing machine drain is located in abasement near enough to use it.

Sealants for Cracks. Joints and Penetrations: Masonrysealants for radon-resistant applications must have good ad-hesion and be durable and clastic. Polyurethane comes ingunnablc grades, and one- and two-part self leveling types.Self-leveling urethancs can be used only on level surfaces asthey arc very mobile. In fact if there is even a small crack atthe bottom of a joint being scaled, the self leveling caulkmay drain out. The popularity of polyurethane is based on acombination of good adhesion even under difficult condi-tions, long service life, good elasticity and easy availability.Copolymer caulks have very similar properties to the poly-urcthancs. Recently some copolymer caulks have been pack-aged as sealants specific to radon control. Siliconc caulkshave also been used in radon control but require more ex-tensive surface preparation for good adhesion. Many radonmitigators have adopted the use of silicone caulks for scalingsump lids and access ports because they make a tight-fittinggasket that can be removed more easily than polyureihane ata future date. Butyl caulk is susceptible to attack bygroundwatcr acids. Polysulfidcs have been largely supplantedby polyurcthancs because the former are more chemicallyreactive with asphalts.

Surfaces should be clean and dry when caulk is applied.Bear in mind that the idea is to get a flexible membrane tobridge between the two surfaces that the crack divides. It isa poor practice to simply fill every crack. Manufacturersusually specify appropriate dimensions for their caulks. Of-ten this is a minimum 1/4 x 1/4 in. For small cracks, it maybe necessary to grind them larger to meet the caulk manufac-turers' specifications. For cracks much larger than 1/4 in., abacker rod should be used to support the caulk so that it canbe applied correctly.

CAUTION: Caulks give off organic compounds. Someof these are carcinogenic. Users are reminded here that theyshould have the Manufacturers Data Sheets for any chemi-cals they use. These sheets identify hazardous aspects in theuse of the products. OSHA requires that contractors havethese sheets available for employees and that a safety trainingprogram be in effect for these products.

4.5 CrawhpacesCrawlspaces are being treated here as a special case of

using the foundation materials to make a mechanical barrier.In this sub-section isolating the living space from thecrawlspace by sealing the floor between the two spaces willbe discussed. A sheet of plywood is a relatively good barrierto radon laden crawlspace air and, as with the other materialbarriers, it is the joints and penetrations that are the prob-lems. The major entry points are through numerous electri-cal, heating, and plumbing penetrations in the house floorand via the return air ducting often located in the crawlspace.Lower air pressure in the house and the return air duct thanin the crawlspace draws radon laden crawlspace air into theliving space of the house.

During construction, all possible penetrations betweenthe crawlspace and the house should be sealed to simplyprevent the passage of radon up into the living areas. At-tempts to seal penetrations can be made by using expandableclosed-cell foam sealants and urethane caulk. Sealing theseareas can be difficult because of limited access even duringconstruction. Areas of particular concern include:

1) openings in the subfloor for waste pipesincluding openings for tubs, toilets, and showers.

2) openings for water supply lines.3) openings for electrical wiring.4) openings for air ducting for the heating,

ventilating, and air conditioning (HVAC)system.

5) openings around hot water heating pipes --Check on code requirements for clearancebetween hot water pipes and wood floors. Thesemay require a special sealant.

6) joints between sheets of plywood.Any sealing around plumbing traps must be done so that

the trap can still be reached and serviced.Return air for the HVAC system should not be suppl

from the crawlspace. It is best to avoid routing return airductwork through the crawlspace, but if it must be, then itshould be thoroughly sealed with duct tape at a minimum. Itshould be understood, however, that duct tape may dry outand fall off. A better approach would be to use seamlessductwork in these areas. The use of floor joists andsubflooring as three sides of a return air plenum should beavoided because of the difficulties encountered in sealing. Ifthe space between the joists must be used, an alternative toducts is to use a rectangular duct to fit the space.

If isolation of the crawlspace is the primary method ofradon-resistant construction being used, the number and sizeof crawlspace vents should be maximized. The March 1988version of Florida's proposed interim guideline for radon-resistant construction (FL88) suggests vents of not less than1 ft2 of vent for each 150 ft: of crawlspace. The proposedguideline also requires that vents be located to provide goodcirculation of air across the crawlspace and should not in-clude registers or other provisions for closure. This require-ment would be impractical in cold climates with water pipesin the cra\vlspace. If there were no water pipes to worry

24

Slab

Watertrappeddrain

Sumppump Check valve

Cover sealed toshallow sump

Figure 4.2 Sealing a Sump Hole to a Shallow Yet Operable Sump.

about, then the floor would need to be well insulated in orderto ensure that a large energy and comfort penalty was notincurred.

Other radon-resistant alternatives besides simple isola-tion of the crawlspace should be considered because of thedifficulties encountered in getting an adequate seal betweenthe house and the crawlspace. These alternatives will bediscussed in Section 5.

A NEWHEP builder in Denver uses an innovative foun-dation technique to simultaneously deal with problems ofexpansive soil and high soil radium and radon content Thefoundation excavation is over-dug to a depth of 10 ft. Cais-son pilings are driven to support the 10-ft-tall reinforcedpoured concrete walls. Band joists are bolted to the walls 2ft above the dirt floor, and a carefully sealed wood subfloor,supported by steel "I" beams and standard size floor joists, isinstalled. The 2-ft-high "buried crawlspace" is actively ven-tilate' by installing a sheet metal inlet duct in one comer ofthe basement, drawing in outdoor air through an above-ground vent A similar duct with an in-line fan is located atthe opposite comer to exhaust air through an above-gradevent Soil gas radon at levels from 3,163 to 4,647 pCi/L wasmeasured at three of these building sites. Soil radium-226content was measured at 1.05 to 1.62 pCi/g. Indoor radonmeasurements were then taken in the buried crawlspaces andin the basements. Measurements were made during thesummer of 1987 with the exhaust fan off, and after 1 day, 1week, and 2 weeks of operation. The results are shown inTable 4.3 (Mur88).

4.6 Coatings4.6.1 Introduction

If waterproofing or dampproofing treatments that areeffective gas barriers and that can be sealed at joints andpenetrations could be identified, then walls could be maderadon-resistant Acceptable dampproofing or waterproofingtreatments are specifically listed in building codes in many

Table 4.3. Result* Using Vented Crawlspace TechniqueBurled Crawl- Basement

House Fan space Level LevelNo. Operation pCI/L pCI/L

11122233

OffOn 2 WeeksOn 2 WeeksOffOn 1 WeekOn 1 WeekOn 1 DayOn 1 Day

999.98427818616.7 C264155 C

.9

.4

.482

)93

).9NOTE: Foltowup measurements were made in trie basements of

Houses 1 and 2 in March 1988 and levels of 06 and 09pCi/L were obtained. The continued effectiveness of thistechnique is assumed to be the result of (he combination ofboth active ventilation in the crawlspace and careful sealing and caulking of all seams, joints, and penetrations ofthe basement floor (MurSfl)

areas of the United Slates; these lists are periodically amendedas new materials come into use. These coatings apply prima-rily to basement walls.

The terms "waterproofing'' and "dampproofing" are of-ten used interchangeably. Briefly, any waterproofing mate-rial can also be used for dampproofing; the converse is nottrue. Waterproofing materials must resist the penetration ofwater under a hydrostatic load. Dampproofing materials arenot expected to keep out water under pressure, but do impedewater entry and block diffusive movement of water throughpores.

Any material which provides adequate protection againstwater should at least limit convecuve soil gas movement.Properly applied waterproofing materials should help blockpressure-driven entry of soil gas.

The most common dampproofing treatment for residen-tial foundation walls is a parge coat covered with bituminousasphalt. The parge coat is used for concrete masonry wallsbut is not necessary for poured concrete walls. This two-

25

stage treatment has been replaced by surface bonding cementin some areas.

Oak Ridge National Laboratory indicates that bitumi-nous asphalt may be attacked by soil and groundwaterchemicals, specifically acids (ORNL88). Bituminous maieri-als may also lose their elasticity at below-freezing tempera-tures . These features render b i tuminous asphalt anundependable waterproofing treatment; in fact, it is listed bycode organizations such as BOCA, CABO, and SBCC1 onlyfor dampproofing.

A number of dampproofing systems are better gas barri-ers than bituminous asphalt. Some are relatively new to theresidential marketplace but have track records in industrial/commercial settings. Others have been introduced into themost expensive residential market or have found applicationsat problem sites. A common feature of these alternatives isthat they arc generally more expensive than bituminousdampproofing. However, a 1981 survey of 31,456 hoase-holds by Owens-Coming Corporation (Da86) found that 59%of homcowncrs with basements reported water leaks. As thesupply of trouble-free building lots dwindles, home buyersmay decide that additional investment is justified, and im-proved dampproofing systems may be developed to addressradon and water problems simultaneously.

4.6.2 Dampproofing/Waterproofing to Achieve aRadon Barrier

The following is a sampling of alternative waterproofingsystems that arc readily available to builders.

Coal tar modified polyurethane: Coal tar modified poly-urcthanc is a cold-applied liquid waterproofing system. TheHLMTM system by Sonncborn is an example of this ap-proach to waterproofing. It is applied as a liquid at the rateof 10-15 mils/coat. The coating dries hard, but has someelasticity. This material may be attacked by acids ingroundwater but can be defended by a protection board. Theperformance of any liquid-applied waterproofing systems islimited by the capabilities of the applicator (it is difficult toachieve even coats on vertical surfaces).

Polymer-modified asphalt: Polymer-modified asphalt isa cold-applied liquid waterproofing system. As with theHLMTM system mentioned above, the quality of the instal-lation depends on the applicator (it is difficult to achieve aneven coaling on a vertical surface). High grade polymer-modified asphalt is superior to coal tar modified polyure-thane in elasticity, crack-spanning ability, and resealability,but inferior in its resistance to chemicals.

Membrane waterproofing systems: Waterproofing ap-plied as a membrane has an advantage over liquid-appliedsystems in that quality control over thickness is ensured bythe manufacturing process. Most membrane systems are alsochemically stable and have good crack-spanning ability. Onthe other hand, effective waterproofing demands that seamsbe smooth so that the membrane is not punctured. Somemasons apply parging to a half-height level and then returnto finish the upper half of the wall. This tends to leave arough section where the two applications overlap and meansthat the waterproofing crew has to grind the wall smoothbefore applying the waterproofing membrane. Thermoplas-

tic membranes may be applied in various ways-affixed towalls, or laid beneath slabs. Thermoplastic membranes arehighly rated for resistance to chemicals and longevity. Rub-berized asphalt polyethylene membranes have superior crack-bridging ability, compared to fu l ly adhered thermoplasticmembranes. (Loosely hung thermoplastic membranes, bytheir nature, have obvious crack-bridging ability in that theyare not bonded to the walls.)

Seams and overlaps must be carefully and completelysealed in order for membranes, to function as radon bamers.The choice of seam material varies with the type of sealant.Manufacturers' recommendations for sealant, procedure andsafety precautions should be followed.

Bentonite: Bentonite clay expands when moist to createa waterproof barrier. Bentonite is sold in various forms,including panels and mats. Bentonite is not as resistant tochemicals as the thermoplastic membranes, nor is it punctureresistant. The major flaw of bentonite as a radon barrier,however, is that it is only tightly expanded when wet. Thisis acceptable for a waterproofing material, but not for a gasbarrier.

•***Surface bonding cement: Surface bonding mortar or

cement is mentioned in some building codes as an approveddampproofing treatment, but not as a waterproofing treatment.A number of manufacturers produce cements and mortarsimpregnated with fibrous glass or other fibers. Some ofthese may be chemically unstable in the alkaline environ-ment of Portland cement

One technique of assembly using surface bonding ce-ment is to dry-stack blocks and apply the cement on bothsides. As an alternative, the block wall is conventionallyassembled with only an outside coating as a positive-sidewaterproofing.

Cementitious waterproofing: A number of additives canbe incorporated into concrete to create cementitious "water-proofing." This type of waterproofing is appropriate only forinterior applications because it is inelastic, does not fcgood crack-spanning ability, and cannot resist hydrostaticpressure.

Interior paint as a barrier: A variety of interior appliedmasonry paints are available. Some of these have been testedby the AEERL laboratory at the EPA. Results of these testsare given in a paper presented at the 1988 Symposium onRadon and Radon Reduction Technology (Har88).

4.7 Membranes4.7.1 Introduction

Membranes of plastics and rubbers that are used tocontrol liquid water penetration and water vapor diffusionare effective at controlling air movement as well. If they canbe adequately sealed at the joints and penetrations and in-stalled intact, then they could also provide a mechanicalbarrier to radon entry.

Construction film is already in common use as a sub-slab vapor barrier in many areas of the country. The currentprevalence and low cost of this material mean that it may beworthwhile to continue its use even though it is an imperfect

26

barrier. It is possible to seal polyethylene vapor barriers atthe overlapped edges, at penetrations, and at the footing; butit may be that the extra effort will not be rewarded withimproved radon resistance.

In Sweden, sub-slab membranes are not required inhigh-radon areas and a tightly sealecFslab is considered to bea more effective radon barrier. The difficulty of achieving acompletely sealed, intact sub-slab membrane is widely ac-knowledged; however, a sub-slab barrier may be worthwhileeven if it is imperfectly installed. Polyethylene constructionfilm (6-mil) can serve as a backup radon barrier to theconcrete slab, even though it is not a complete radon barrierby itself. The barrier may continue to function, even withpunctures, if incidental cracks and holes in the slab arealigned with intact areas of polyethylene.

In summary, it is worthwhile to continue the installationof a vapor barrier that serves the added valid function ofmoisture barrier. More comprehensive installation measuresand more expensive materials may be merited in areas wherethe radon source is strong because of either high radonconcentrations or high soil gas flow rates.4.7.2 Types of Membranes Available

Polyethylene film: A vapor barrier of polyethylene filmis a typical sub-slab feature in many areas of the country.The intent of the vapor barrier is to prevent moisture entryfrom beneath the slab.

Installation of any sub-slab membrane is problematicbecause an effective barrier should be both well sealed andintact. Builders who use polyethylene under the slab indi-cate that achieving a complete seal at all laps and edges andaround pipe penetrations is difficult. It is difficult to seal thepolyethylene to the footing because the weight of the con-crete tends to pull it away from the walls during the pour.There is also a high probability that the vapor barrier will bepunctured during installation. It has been observed that even10-mil polyethylene in a heavy felt membrane is likely to bepunctured during installation.

Another issue is the stability of polyethylene vapor bar-riers. Polyethylene is known to be harmed by ultraviolet(UV) exposure. One radon mitigator has found polyethyleneunder slabs in Florida that deteriorated in less than IS years;more frequently, polyethylene of comparable age is in mintcondition.

Polyethylene films are manufactured with an array ofadditives selected to support specific applications. Durabil-ity varies according to the additives employed, film thick-ness, length of UV exposure, temperature swings, and otherfactors. Resins used in polyethylene manufacturing haveimproved over time, so that the life expectancy of polyethyl-ene film in 1988 is longer than for the films used in the1950s, 1960s, and 1970s. The durability of polyethylenefilms in current use depends on the contractor's selection andproper storage of the appropriate film for the job.

On the other hand, there is no evidence to support theassertion that polyethylene vapor barriers deteriorate withexposure to soil chemicals. Construction film is a low-density polyethylene. High-density polyethylenes are used

for storage and transportation of an array of chemicals.Polyethylene is chemically stable, but may be adverselyaffected by aliphatic hydrocarbons (such as hexane. octane.and butane) and chlorinated solvents. It does not appear tobe reactive with the acids and salts likely to be encounteredin soil and concrete. No sub-slab membranes have beenidenufieJ^rmanufactured specifically for radon control.However, several products are promising alternatives to 6-mil polyethylene construction film.

Polyethylene -coated kraft.paper vapor barrier is avail-able in 8 x 125 ft rolls. Overlaps of 6 in. are marked on thepaper with a printed line. They can be sealed with polyethyl-ene tape. This material is attractive to contractors because itis more puncture-resistant than 6-mil polyethylene construc-tion film, but less expensive than many alternative products.

Polyethylene-based membranes are manufactured for usein hazardous waste landfills, lagoons, and similar applica-tions. Two of these products have recently been tested todetermine their effectiveness as barriers against radon diffu-sion. (In most cases, diffusive flow is considered of little orno significance as a mechanism of radon entry compared toconvective flow.) A 20-mil high-density polyethylene tested99.9% effective in blocking radon diffusion under neutralpressure conditions. A 30-mil low-density polyethylene tested98% effective in blocking radon diffusion under neutral pres-sure conditions.

A material composed of a double layer of high-strengthbubble-pack with aluminum foil bonded on both sides isavailable. It has a high compression strength and doubles asan insulator. Concern exists over its fragility and suscepti-bility to pinhole punctures. Both foil-faced membranes canbe punctured, but the double bubble-pack offers some defenseagainst complete penetration. Punctures are easily repairedwith aluminum tape, which is also used at seams. A well-made seal is diffusion resistant; however, gas can migratethrough wrinkles in the tape. The fragility of the material isbelieved to be a significant limiting factor in using it underthe slab or as a penmcter insulation.

Another available product has two faces of aluminum foilover a core of glass scrim webbing; it is coated with asphi.t.The membrane is 0.012 in. thick. This material has not beentested as a barrier against diffusive flow of radon, but itsperformance should be similar to that of other foil facedproducts. Seams are sealed with aluminum tape.

PVC membranes have been used as a sub-slab mem-brane during radon mitigation work in existing houses. PVCmembranes are usually sealed with solvents and were devel-oped as roofing membranes.

Another product, EPDM™ is a rubber-like material. Itcomes in 60-mil thicknesses in 100 ft by 61-1^2 in. rolls.EPDM also comes in 45-mil thicknesses in 25 by 60 ft rolls.This product has gained popularity as a ground cover incrawlspaces because of its durability qualities.

Note: EPA does not endorse any brand names or products mentioned inthis manual

27

4.8 Mechanical Barriers Applied to the SoilIt has been suggested that mechanical barriers could be

applied to the soil beneath the foundation that would preventthe migration of radon into the building. As of this writingthis is an untried approach. If it works it would have thebenefit of being less susceptible to occupant behavior, futureremodeling activities and mechanical failure of fans. Twoapproaches have been brought forward. One would ust; aninjection of slurry composed of clay to dramatically reducethe permeability of the soil. This technique is used in theconstruction of lagoons, landfills and dams. The second ideais to spray the soil surface with a polymer modified asphalt.This technique has been used to cap landfills to control therelease of methane and other organic compounds.

4.9 Drainage Boards for Soil Gas and RadonControl

Soil that was excavated from the basement is commonlyused as backfill against foundation walls. This should not bethe case where the site material contains clays and silts,particularly organic clays and silts. If local soils are notappropriate, the builder may use gravel to backfill.

Drainage boards are a substitute to backfilling with gravel.Drainage boards have been used for a number of years,particularly in commercial projects and underground houses.Depending on the cost of hauling sand and gravel, a drainageboard may be a cost effective alternative.

It has been hypothesized that a drainage board which islaid up against a house wall might provide an air buffer Jiatcan break the pressure connection between the soil and thehouse interior. This is rather like having a hole in your strawwhen drinking through it. No systematic research has beendone on this topic.

4.10 Summary of Recommendations forMechanical Barriers

4.10.1 Rules of Thumb for Foundation Walls• Use reinforcing to limit cracking.• Seal pipe penetrations.• Cap masonry walls with bond beam or solid

blocks.• Dampproof walls (interior as well as exterior

on masonry walls). '4.10.2 Rules of Thumb for Slab and Sub-Slab

BarriersMake a slab edge joint that is easy to seal(tooled joint or zip-off expansion joint material).

• Caulk perimeter crack and control joints withpolyure thane.

• Reinforce slabs with wire mesh to help preventlarge cracks and use control joints - - caulk thecontrol joint.

• Drain to daylight if possible, or to a drywell orsewer. If you must use an interior sump pump,seal itAs a precaution, use interior footing drains (inaddition to exterior drains) and 4 in. of No. 2stone below the slab that drains to the buildingexterior. This way, sub-slab ventilation can beadded easily in case a problem is discoveredlater (Br86).

4.5.These suggestions are illustrated in Figures 4.3, 4.4 and

BoM beam orsol*J cap block

Reinforce walls and slabsto reduce cracking

Coal ntenof wan Dampproofing orwaterproofing

Exterior parge coatand dampproofmg

Membrane beneathslab

Gravel drainagelayer

Seal around pipepenetrationsand at pints

Interior and/orexterior footingdrain

Figure 4.3 Summary of Mechanical Barrier Approach for Basument Foundation*.

28

Seal penetrations,and joints

Install membrane beneath slab

Permeable aggregate ordrain strip network

Rgura 4.4 Summary of Mechanical Barrier Approach for Slab-on-grade Foundations.

Foam insulationInstall vents inunventedcrawlspace

Stone pebbles underslab

Vented Crawlspace Unvented Crawlspace

Figure 4.5 Summary of Mechanical Barrier Approach for Crawlspace Foundations

29

Section 5Site Evaluation

IntroductionWhen siting new residential construction, builders would

like to determine the potential for radon problems associatedwith each building site. Unfortunately, at present there areno reliable, easily applied methods for correlating the resultsof tests made at a building site with subsequent indoor radonlevels contained in a house built on that site. Houses varysignificantly in their ability to resist radon entry. Bedrockand soils interact in complex ways with dynamic housebehavior and environmental factors. There are too manycombinations of factors that cause elevated indoor radonconcentrations for simple correlations to exist

In an effort to evaluate the risk of an indoor radonproblem occurring in a home built on a particular site, re-searchers have made many types of measurements. The mea-surements commonly made include:

• soil and bedrock radium concentrations• radon measurements in the interstitial soil and

bedrock pores• permeability of the soil or bedrock• airborne radiation measurements.In addition to the above measurements, indexes using

soil concentrations in combination with permeability mea-surements have been suggested by some researchers (Ku88,Pe87). As elaborated on later in this section, these methodshave been successful in establishing relationships betweensome of the site measurements and indexes, and indoor radon.concentrations for specific areas and regions.

Although substantial progress has been made by investi-gators using geologic, radiation and other site data to predictareas of high radon risk, it still requires many site measure-ments to adequately assess a particular site. The judgementthat needs to be made is whether or not it is more costeffective to make the building radon-resistant to begin with,or to put the money into site evaluation and possibly avoidthe need for radon-resistant construction techniques.

5.2 Radon in the soilIn buildings with indoor radon concentrations greater

than 4 pCi/L, the majority of the radon is produced in the soiland enters the building through foundation openings. Theradon gas found in soils is a product of the decay of radium-226, a radioactive chemical element present in trace levelsin many types of soils and rocks. Radium and radon areelements that are pan of the uramum-238 (U-238) decayseries. See Figure 2.1 for details. Uranium-238 decays

through a chain of radioactive elements. Radiation is re-leased as each element decays. Radon will mov«?through theporous soil or shattered bedrock by convection and diffusionbecause it is a gas. The other elements in the U-238 serieswill not easily move through the soil because they are par-ticles and not gases. The amount of radon that enters thehouse depends on the amount of radon gas or radon parentcompounds found in the soil beneath the house. Thepermeability of the soil, the presence of faults and fissures inunderlying and nearby rock, openings between the house andsoil, and the driving forces that move soil gas along path-ways into the house also contribute to the total radon levels.To have a radon problem requires radium nearby, a pathwayfor the gas to move through the soil or rock, a driving force,and openings in the foundation.52.1 Attempted Correlations Between Indoor

Radon and Measurement Made at SitesSeveral studies have attempted to make simple correla-

tions between radon or radium concentrations in the soil andindoor radon concentrations (ERDA85, Na87). No signifi-cant correlations were made between these variables.

The Florida Statewide Radiation Study performedby Geomet (Na87) illustrates the variability of radon-resistantconstruction and the resulting problem of trying to correlatesoil radon levels with indoor radon levels. The study reportsover 3,000 paired soil radon and indoor radon samples. Atotal of 77 soil radon readings were greater than 1,000 pCiyL.The two highest soil radon values were 6587.0 and 6367.2pCi/L. Interestingly, corresponding indoor radon levels forthe two highest sites were 6.8 and 0.2 pCi/L, respecu vely. Inaddition, almost half of the houses with soil radon levels inexcess of 1,000 pCi/L had indoor radon levels of less than 4pCi/L.

The Florida data reported by Geomet have been evalu-ated and the houses listed in order of highest measuredindoor radon levels. This analysis is shown in Table 5.1(Pu88 and Na87).

It is clear from Table S.I that soil radon measurementswhich varied over an order of magnitude produced signifi-cantly less than a factor of 2 difference in the indoor radonlevels. Predictions of radon potential based on soil radonmeasurements would be highly suspect based on these data.

In Sweden, soils have been classified as having high,normal, or low radon risk potential based on soil radonconcentration and soil permeability. The soil radon valuesand permeability characteristics used to establish the soil

31

classifications and the corresponding construction require-ments are given in Table 5.2 (Sw82). Factors other than >oilradon that are considered before classification in Sweden arepermeability, ground humidity, and soil thickness. ClearlySweden has decided that a number of factors must be ad-dressed to evaluate the radon problem potential of a site.Using the suggested soil radon concentrations but not thepermeability guidelines included in the Swedish soil classifi-cation scheme, no building restrictions would have beenrequired for many of the houses surveyed in Florida withindoor radon measurements greater than or equal to 4 pCi/L.

Fifteen of the houses in the Florida study with measure-ments greater than or equal to 4 pCi/L had soil radon con-centrations less than or equal to 200 pCi/L. This correspondsto 13.5% of the houses with soil gas less than 270 pCi/Lbeing above the EPA action level of 4 pCi/L. Nineteen ofthe 48 houses (39.6%) lhat had radon in the soil over 1,350pCi/L had radon levels in the house less than 4 pCi/L. Thismeans that almost 40% of the houses that would have beenrequired to be built "radon-safe" under the Swedish guidelineswere already below 4 pCi/L using standard constructionpractices.Table 5.1 Florid* Survey Soil Radon and Corresponding Indoor

Radon Concentration*.

Indoor Radon ConcentrationpCI/L

Soil Radon ConcentrationpCI/L

32429528025325325024 1229229

1591 '1846978695559200 '3539

. . .439.7

.3561.321445,

Table 5.2 Swedish Soil Risk Classification Scheme and Build-Ing Restriction*.

Soil Radon PermeabilityConcentration of Soil

pCI/L

RiskClassification

BuildingRestriction*

< 270

270-1350

>1350

Very low permeability(eg . clay and silt)

Average permeability

High permeability(eg. gravel and

coarse sand)

Low Use conventionalconstruction

Normal Use radon-protec-tive contruction

High Use radon-safeconstruction

The Florida survey was an ideal opportunity to comparesoil radon and corresponding indoor radon levels in slab-on-grade construction. By looking exclusively at slab-on-gradehouses, additional variables, including depth below grade ofbasements, and height and ventilation rates of crawlspac:s,are eliminated. These variables, which are inherent in com-mon construction techniques used throughout much of therest of country, exaggerate the difficulty correlating indoorair radon and soil radon levels.

The major drawback in using the Florida study to sup-port the correlation between indoor and soil measurementswas that the indoor measurements were obtained from 3-dayclosed-house charcoal measurements, and soil radon wasobtained from 1-month alpha track measurements buried 1 ftbeneath the soil surface. Comparisons of charcoal and alphatrack data are generally not recommended since they arequite different measurement techniques, and represent radonlevels over different time periods. However, the study wassubjected to numerous quality control checks including de-ployment of alpha track detectors in 10% of the houses toobtain a check on indoor air measurements made by charcoalcanisters. In spite of the measurement drawbacks, the studyindicates that soil radon measurements taken alone are not adependable predictor of potential indoor radon concentration.

5.2.2 Indexes using Permeability and Soil RadonConcentrations

By making an index from the product of soil radonconcentrations and soil permeabilities, a better assessmentcan be made of the risk of a problem on a given site. ARadon Index Number (RIN) has been applied to three arein New York state that have sandy, gravelly soils and pre-dicted w i t h some confidence the geometric mean of indoorradon concentrations using the geometric mean of the soilradon concentrations and the geometric mean of the squareroot of the soil permeability (Ku88). The results of thiseffort are summarized in Table 5.3. This research also pointsout barriers when applying this technique more widely with-out a substantial amount of additional work. First, the indexmust be modified by a depth factor when the soil depth to animpermeable layer (water table, some bedrock, clay) is lessthan 10 ft. Second, the soil radon concentrations in all threeareas *ere typical of most soils in New York state only. Theyranged from slightly below to slightly above the statewideaverage for radon levels in gravel.

Using the permeability and soil radon measurements forthe gravel soils in New York state to compare to the Swedishguidelines would result in a recommendation for radon-rcsrtant techniques to be used in a large fraction of new house _,in all the areas listed except Long Island.Table 5. 3 Geometric Meana for Soil Gas Radon-222, Soil

Radium-226, Permeability, RIN and IndoorRadon- 222.

Study Area Soil Gas Soil Permeability RIN* Basement(Soil Type) Rn-222 Ra-226 Rn-222

pCi/L pCi/g cm2 x 10-6 pCi/L

Cortland Co(Gravel)Albany Co(Gravel)Rensse'ear Co(Gravel)Slate Wide(Gravel)Long Island(Sand)Onondaga Co

551

675

1.003

602

164

1.671

NA

1.0

1.0

12

04

28

120

67

1.1

4 1

022

012

190

180

110

120

08

90

172

202

9 4

NA

10

6 1

• RIN = 10 [soil gas radon (pCi/L)](permeabihty) 05

32

In EPA Office of Radiation Program's New HouseEvaluation Program (NEWHEP), two builders in the Denverarea, two in Colorado Springs, and one in Southfield, Michi-gan, installed various radon-resistant features in houses dur-ing construction. A sampling of subsequent measurementsof indoor radon, adjacent soil gas £?don, and soil radiumcontent is summarized in Table 5.4 (Mur88).

The major difference between these data and the Floridasurvey data in Table 5.1 is that this portion of the NEWHEPdata was collected from newly constructed houses wherepassive radon-resistant construction features were being tested.There are no data on control houses in the same area that didnot have those built-in features, making it difficult to com-pare soil radon measurements to indoor radon concentrations.It appears, however, that passive-only building techniques donot consistently result in indoor radon levels below 4 pCi/L.All five of the builders in the NEWHEP are currently experi-menting with or are considering the installation of active,fan-driven sub-slab ventilation systems. Results are beingmonitored (Mur88).Table 5.4 Indoor Radon and Soil Radon Measurement* In

Colorado and Michigan.

Indoor RadonHouse In BasementNo. pCI/L

HECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOHECOI-ECO

73007395739574197423742374257425742774277448745574567458745874597459

HEMI 30001HEMI 30002HEMI 30003HEMI 30004HEMI 30005

5914.51675.779—15...30--1180723723509—1809421.736

Radium-226Soil Gaa Radon In Soil

pCI/L pCI/g

_——71010021779620...14301316930—

13 (90 cm)3 (Surface).9 (90 cm)

.3 (90 cm)4 (90 cm)3 (Surface).7 (90 cm).1 (Surface).4 (90 cm)

1240 04 (Surface)996 0.6 (90 cm)20303881095 11014 1—————

0 (Surface).9 (30 cm)

• Radium-226 in soil was measured at two lots in this housing devel-opment One lot measured 0.79 pCi/g and (he second lot measured0.91 and 1.2 pCi/g on two soil samples. These measurements werenot made at the same houses where indoor radon was measured,so no direct correlation is possible. The soil test results are onlyindicative of some radon existence in this same geological area.

52.3 Variations in Spatial and Temporal SoilGas Concentrations

Aside from the difficulty correlating soil radon measure-ments with indoor radon measurements, various field studieshave also shown that obtaining a representative soil gasmeasurement is difficult. Soil gas radon measurements weremade with a permeameter in seven central Florida houses inNovember 1987 (Pe87), A permeameter is a soil-gas and

permeability measurement device that allows soil-gas to besampled at various depths. In this study the radon concentra-tion was the average of samples collected at depths of 60,90,and 120 cm. Four to six samples were collected in the yardof each house at distances of 0.5 to 4.5 m from the housefoundation.? Soil radon concentration measurements in eachof the sevelri'yards varied by factors of 1.3 to 6.4, with anaverage variation of 3.1. In another study in the Piedmontarea of New Jersey (Ma87), soil radon was measured in thefront, side, and back yards of seven houses. Grab samplesand 3-month alpha track sample's were obtained from a depthof about 1 m. The grab sample radon measurements variedby a factor of 50 between houses and by as much as a factorof 46 between test sites at a single house. The averagevariation for each of the seven houses was 12.9. The alphatrack results showed seasonal variations of approximately anorder of magnitude difference between fall and winter/springsoil gas levels. The soil alpha track results did not comparein general with the results obtained by grab sampling. Forexample, a factor of 30 increase in radon from the front toback yard was observed in one house by grab sample data,while alpha tracks taken in the front and back yards weresimilar. In a second house, the opposite was observed: grabsamples collected in the front and back yards varied by lessthan a factor of two, while alpha track measurements in thesame yards varied by a factor of 14 (Ma87). In anotherseven home study in the Piedmont area (Se89) large variabil-ity in permeability measurements and soil gas rador concen-trations was seen. Spatial variation in soil permeability atindividual homes ranges from a factor of 10 to 10,000.Temporal variations in soil permeability at a given test holeranged from a factor of 2 to a factor of 90. Spatial variationsin soil gas radon ranged from less than a factor of 2 to afactor of 200 for a given site. Temporal variations in soil gasradon from less than a factor of 3 to a factor of 40 for a giventest hole.

As indicated from the data, indoor radon concentrationscannot yet be predicted from soil radon values. The possi-bilities are not promising for designing a device and/or tech-nique that builders can rely on to exclude building sites aspotential indoor radon problems. As shown by the Floridaand New Jersey data, multiple measurements woulu be re-quired at each building site, and even those measurementscan vary by orders of magnitude. Until the lot has beencleared, rough grading completed, and the foundation holedug, access to the soil that actually produces the radon gas inthe house is difficult, if not impossible. Few builders woulddecide not to build on a lot after they have incurred the costsof purchasing the lot and digging the foundation. In addition,many houses use fill din brought in from other locations.Unless the fill din is also characterized, additional radonpotential may be missed or, on the other hand, the actualpotential for radon entry may be overstated.

In summary, at present individual building lots cannotbe characterized reliably for radon potential, and because ofthe inherent problems that have been identified, buildersshould not expect to be able to make these measurements orpay someone else to make them reliably in the near future.Aggregate data on radon in soils can only be evaluated on acommunity wide basis at this time. There is hope that thesedata can be used statistically to predict large areas with a

33

high probability of residential radon problems. Work toenhance the accurate prediction of radon-prone areas is con-tinuing within EPA and among other research organizations.

5.3 Radon Observed in Nearby HousesAnother approach to estimating the nsk of a radon prob-

lem on a particular site is to examine measurements fromnearby existing houses. In EPA's Radon Reduction Demon-stration Program for existing houses, those with elevatedradon levels generally have been identified through priorhigh-radon measurements in other houses in the neighbor-hood. Although it is possible to have isolated pockets ofradon gas in the soil beneath a single house, most radon-prone houses are located in a geological setting common tomost other houses in the general vicinity or region. Becauseof the many variables that affect radon entry into a house,homes with elevated radon can be found adjacent to houseswith very little radon. However, statistically, the presence ofan elevated radon house in a neighborhood or a significantnumber of elevated houses in an area as large as a county orZIP Code area increases the likelihood of other elevatedradon houses in the same area.

A classic example of one elevated radon house leadingto the discovery of other elevated houses in the area occurredin Clinton. New Jersey, in March 1986. A homeowner in theClinton Knolls subdivision read about the radon problem inthe Reading Prong area of Pennsylvania and decided toobtain a charcoal canister and measure the radon level in hisown house. When he received a very high radon reading, henotified the New Jersey Department of Environmental Se-lection (NJDEP). The NJDEP surveyed the neighborhood,making charcoal canisters available to homeowners who werewilling to have the radon level checked in their houses. Thesurvey showed thai 101 out of 103 houses tested had radonlevels above the EPA action level and over half of the houseshad more than 25 limes the action level (Os87a).

The Clinton experience can be contrasted with radonobservations in Boyertown, Pennsylvania, where houses withradon concentrations over 500 times the EPA action levelwere found adjacent to houses below the action level (Py88).Therefore, the presence of elevated rac? on houses in a neigh-borhood is at best only an indication that the probability ofhaving a radon problem has increased.

5.4 Airborne MeasurementsThe State of New Jersey has been able to correlate

airborne radiation measurements to clusters of buildings withelevated indoor radon (Mu88). In this study, researcherscompared airborne gamma-ray spectromeier data lo indoorradon data to see if any trends emerged. For the conditionsin New Jersey it was found that areas with airborne anoma-lies of 6 ppm equivalent uranium or greater were likely tohave clusters of homes with elevaied radon. This could be avaluable tool for health officials who are trying to make thegreatest public health impact for the most reasonable cost.Inasmuch as it alerts a region 10 be wary, it is helpful, but iiis probably noi of much benefil in the assessment of anindividual site.

5.5 Radon in WaterBetween 2% and 5% of the radon problems found in the

U.S. can be attributed to radon in water (.EPA87). The mostsignificant radon-in-water problems observed so far in iheUnited States have occurred in the New England states.Houses with individual or community wells seem to have thegreatest potential for a problem since the water in thosesystems is usually not well aerated.

Radon dissolves into groundwater from rocks or soils.When the water is exposed to the atmosphere, some of thedissolved radon is released. As a rule of thumb, there is anincrease of about 1 pCi/L in the air inside a house for every10,000 pCi/L of radon in the household water (EPA87).Higher radon levels have been observed in individual roomswhen water is heated or agitated, such as during shower use(Os87c). Builders should be aware that houses that requiregroundwater as the house water supply could have a radonproblem. The only way to be certain that the groundwater isnot a potential radon source is to have the water from thewell tested. Some states and private companies provide testkits for this purpose. It should also be noted thai ra^concentrations in water, like radon concentrations in the a»<can vary significantly.

If a well has not been drilled, a nearby well may be anindicator of potential radon problems. Identifying potentialradon-in-water problems by using the results from adjacentwells is subject to the same problems that were mentioned inSection 2.3.3. There is no guarantee that the neighbor's wellis producing water with the same characteristics as the newwell will produce since it may not be from the same stratum.The limited data available on houses with radon-in-waterproblems indicate that adjacent houses with similar wellssometimes produce similar radon-in-water problems andsometimes do not. However, few isolated radon-in-waterproblem houses have been observed.

In summary, because of the small percentage of houseswith radon-m-water problems, few builders will have to dealwith this issue. However, if a house is being built in an arknown to have many houses with radon-in-water problems,drilling the well and testing the water supply prior to con-struction are advised. If a house is built prior to identifying aradon-in-water problem, resolving the problem can be moredifficult since space will not have been allowed for theradon-in-water mitigation techniques available.

5.6 Radon in Building MaterialsA small percentage of the buildings in the United States

with indoor radon concentrations in excess of 4 pCi/L can beattributed to building materials. Most of the building mate-rial problems have arisen from the use of known radium- oruranium-rich wastes such as aggregate in block or as backfillaround houses. None of the houses studied in the EPARadon Reduction Demonstration program have had anyidentifiable problem associated with radon from buildingmaterials.

Builders should be aware that this is a potential problembut, unless building materials have been identified as ra-dium- or uranium-rich, the chance of obtaining radon frombuilding materials is very slim.

34

'?• Section 6 4^%Planned Ventilation: Mechanical Systems

IntroductionNew construction offers the opportunity to plan and

install mechanical equipment so that fresh outdoor air issupplied to the living space and so that the air pressurerelationships between the inside of the building and theoutdoors reduce the influx of soil gas. This approach requiresa better understanding of moisture and airflow building dy-namics than the others covered in this manual. For example,it is important to understand what effect manipulatinginterzonal air pressure differences will have on the risk ofcondensation in the building shell, the entry rate of soil gas,the comfort of the occupants or the risk of increased spillageand downdrafting of combustion devices. By careful plan-ning, the risk of these and other potential problems can bereduced; however, no systematic research has been done toevaluate this approach for radon control. Many variablescome into play in trying to design a mechanical system andbuilding shell that interact with the environment in the waysbest for the health of the occupant and the building itself.

6.2 Interdependence of Mechanical Systems andClimate

Traditionally, residential mechanical equipment has beentreated as independent devices which have little or no impacton the rest of the building other than the obvious statedpurpose. Bath fans, dryers and kitchen ranges are assumedto exhaust moisture, lint and cooking by-products, but tohave no impact on the performance of chimneys. Instanceshave been reported that show this is not the case, that insome houses fireplaces and other combustion appliancesbackdraft (CHMC84) when one or more of the exhaust fansare in operation. Houses have been reported in which theoperation of exhaust devices increases the radon concentra-tion (Os87b). Houses have been found in which pressuredifferences between different rooms of the house caused byHVAC distribution fans have increased energy costs (To88),occupant discomfort (To88, Ne88). condensation in thebuilding shell (Ne88) and radon concentrations in parts ofthe houses (Hu88, Ru88). All of these effects are the resultof air pressure relationships created by the interaction ofmechanical equipment, indoor/outdoor temperature differ-ences, wind velocity, and moisture and radon availability.

To a large extent wind, temperature, moisture and radonare beyond the control of the residential designer or builder.True, good drainage practice and the techniques outlinedearlier in this manual can divert moisture and radon from abuilding, but the amount of rainfall or radon produced isindependent of anything a builder can do. The pieces of this

house dynamics puzzle that the builder or designer can affectare the mechanical devices used in the building.

6.3 Guidelines for Planning the Mechanical SystemSpecific guidelines for planning mechanical systems so

that they minimize problems resulting from their interactionwith each other and other climate-driven building dynamicsare impossible to determine at this point. The major reasonfor this is that buildings constructed on different sites indifferent climates have very different behavior. For an ex-ample, a ranch house built in Florida has a warm, humidclimate with which to work. This means that the spaceconditioning system is probably dominated by air condition-ing and may also incorporate dehumidification. If the samehouse were located in Arizona, the cooling need would bethere but there would be no need for dehumidification. If thesame house were built in Minnesota the space conditioningwould be a heating system and might require dehumidifyingin the summer and humidifying in the winter. In the Floridahouse a case can be made for locating a vapor barrier on theoutside skin of the building because the risk of condensauonin the building shell is near the cooler indoor surface. InArizona, there is seldom the risk of condensation because ofthe small amount of water present in the environment InMinnesota, the risk of condensation in the building shellwould be at the cool outside surface near the siding. In termsof risk of condensation it would be acceptable to pressurizethe Florida house to control radon, because, as the outgoingcool interior air is wanned up, the risk of condensationdecreases. Pressurizing the house in Minnesota is almostcertain to result in condensauon during the winter months, asthe warm interior air cools down on the way through thebuilding shell.

At this time a cohesive body of knowledge that hasenough depth to make recommendations for different siteconditions within the several U.S. climatic regions does notexist. However, many individuals do have enough insight todesign intelligently for their own regions, and there areguiding principles that are general enough to apply for allsituations.

Guidelines: Preserve the intended purpose of all me-chanical devices. A heating system should still deliver therequired amount of heat in a short amount of time. Exhaustfans should remove the moisture, fumes and contaminants.

Be sure applicable codes and standards are followed:Begin with the life and safety codes. The intent of thismanual is to reduce the risk resulting from radon, but not in away that increases other risks. Especially important in this

35

regard arc the National Fuel Gas Code (NFPA54), NationalFire Protection Cede (NFPA1) and the National ElectricCode (NFPA70). Also the CABO One and Two FamilyDwelling Code (CABO86) will be very helpful. There arethousands of code jurisdictions in the U.S., therefore manyissues will have to be dealt with locally.

Plan to reduce soil gas entry: If possible, plan the me-chanical systems so that soil gas is not drawn in by lowerair pressure in the basement or ground floor rooms (slab-on-gradc and crawlspace). Efforts along these lines can bemade by minimizing the amount of air drawn from thoserooms by exhaust fans, conditioned air return ductwork le.iksand grills and sealing bypasses that penetrate floors. Air canalso be supplied to these spaces to make up for the amouni. ofair exhausted. If the exhaust air rate equals the supply airrate for a single zone, then pressure differences should beminimized. Supply air can cautiously be increased to pres-surize these spaces and prevent soil gas entry, but the effecton moisture dynamics, combustion equipment and code ac-ceptability must be kept in mind. An example of this is therelatively common practice of opening warm or cool airsupply grills in a conditioned basement. This uses condi-tioned air and the air circulation blower to pressurize thebasement (or at least reduce the negative pressures).

Plan to supply air to the areas of the house that needfresh air: A planned mechanical system also allows thebuilder to direct fresh air into the living spaces. This willreduce radon concentrations by diluting it with outdoor air.Depending on how it is supplied, it may also reduce thedriving forces that draw soil gas into the building. Supplyair will be drawn in by the mechanical devices, stack effectand wind pressures that exhaust air from the building. Theincoming air will enter either through the unintentional cracksand holes left in the building or through passive vents natcan be installed in the building shell. Passive vents allow ihebuilder to let the fresh air in where it is wanted. Bedroomclosets are a typical location. Supply air can also be poweredby a fan and ducted to the areas where it is wanted. Healrecovery ventilators are a well established method of doingthis, lii either case fresh air will be added and the pressuredifference between inside and outdoors, will be reduced.

Caution: Take no risks with carbon monoxide. This is aspecial warning to carefully ensure that combustion productsare properly exhausted from the house. Of course the placeto begin is with the appropriate codes (UMC, NFUC, CABO,NFC) but keep in mind that even though something is notagainst code it may still be dangerous. For example, asystem that backdrafls a fireplace because it removes airfrom the upstairs of a house might not violate any codes, butis certainly a hazard. Many new heating plants either arepower vented or have dedicated outdoor combustion air.

The two most generally applicable and useful guidelinesfor planning are :

Air moves from higher to lower pressures• Lowering temperature increases relative

humidityThese two rules help to predict the effect of air exhaust

and supply on the transport of radon and moisture and whetheror not to expect increased or decreased risk of condensation.

6.4 Two IllustrationsHere are two situations illustrating the issues involved in

trying to understand the interactions between the mechanicalsand ihe climate. These are illustrations. They do not apply toevery house in the climates described.

First, consider a house in a cold, humid climate. Theway it ordinarily operates is as follows. The warm inside airexits through cracks and holes at the top of the building. Thewarm air leaving through these cracks and holes is coolingdown as it leaves, increasing the possibility of condensation.The suction placed on the lower part of the building in-creases the flow of radon laden soil gas into the basementwhere it is drawn into ihe leaks in the cold air return anddistributed to the rest of the house by the warm air circulationsystem. All of the pieces in this scenario are likely to occur.Other things that could present problems might be bathroomfans that do not have much airflow or are vented into theattk.

If the upstairs portion of the house had the area of cracksand holes into the auk and walls reduced, then exhaustinrsmall amount of air from the house would draw outdoor a **1

in through the remaining cracks and holes. This would/educe the risk of condensation in the building shell becausethe air being pulled in would become warmer, lowering itsrelative humidity. However, exhausting air from a tighterhouse might increase the amount the furnace downdrafts andthe influx of radon.

Using a furnace that draws combustion air from out-doors, or that is power-vented, solves the downdraft problemand probably has little effect on the radon influx whencompared to a furnace that uses indoor air for combustionpurposes. If it is desirable for the upstairs part of the houseto run slightly negative to eliminate moisture, ensure that theheating system has been designed so that backdrafting willnot occur when bathroom, laundry, and kitchen fans areused. If a centralized exhaust ventilation system is used,remember to vent dryers and kitchen ranges separately. It '-poor practice to have grease soaked lint with a fan blowiair over it in the event of a fire.

If the air exhausted from the upstairs part of the house isdiverted into the basement, the basement might be slightlypressurized and the influx of soil gas stopped. If the air leaksbetween the basement and upstairs and the basement andoutside have been sealed, then a smaller volume of air willbe able to pressurize the house. If the basement is insulatedalong the perimeter walls, it would be possible to use the airdistribution ductwork to pressurize the basement and depres-surize the upstairs. This could be done by planning thedistribution ductwork so that it is easy to seal the joints andthen opening grills in the supply ductwork. For this to be aneffective radon control, the fan would have to run all thetime. A two speed distribution fan could be used that wouldrun on low speed all the time and be boosted to high speedwhen heating or cooling is called for.

Ventilation systems could further reduce indoor radonlevels by dilution with outdoor air, and, depending on how itis distributed, could reduce driving forces that draw in soilgas. If outdoor supply air is added to the retum-air side ofthe ductwork then some (50 to 100 cfm) ventilation air

36

*ould be introduced and distributed to the house wheneverthe fan was running. Some new heating systems combineheat recovery ventilation (HRV) with warm air space condi-tioning. This would add about 200 cfm of fresh air when-ever the HRV was operating and 50 cfm whenever thecirculation fan was running. The American Society of HealingRefrigeration and Air Conditioning Engineers is currentlyrevising their residential venulauon guidelines to recommendthe capability of providing one-third of an air change perhour i AC FT) for residences. An HRV would provide that fora 4500 ft: house with 8 ft ceilings, and makeup air for thereturn ductwork would meet that for an 1100 to 2200 ft1

house with S ft ceilings. In addition to radon control thisamount of ventilation has the benefits of control of theunavoidable contaminants released by washing, cooking andbody functions. In a heating climate where there is moderateto heavy rainfall, powered ventilation in the winter can beused for humidi ty control.

Summari/.ing, a mechanical system that is planned locontrol indoor air contaminants (including humidity, radon,combustion gases and body odors) and reduce the risk ofcondensation in the building shell in a cold humid climateshould include:

power-vented or dedicated outdoor combustionair heating systemsdcprcssurizcd upstairs / pressurized basement(possibly using the distribution system)

• air supplied to the building with or without heatrecovery

• tightened building shell to minimize the amouniof air needed lo pressurize the basement and lolower neutral pressure plane

Situation Two is a house constructed in a warm humidclimate. It is a single story slab-on-grade house with aiiconditioning in the attic. There is a single return air grilllocaied in the hallway lhal leads lo ihe bedrooms. When iheair handler is not moving air, the conditioned indoor air masstends to create a reverse stack effect preventing soil gas fromentering. When the air handler is running the house at 2 Panegative pressure, it overwhelms the reverse stack effectbecause the supply ducts in the attic are far more extensivethan the returns and have more leaks. When the bedroomdoors arc closed ihe entire living area goes to about 10 Panegative pressure. In both of these lower indoor air pressureconditions soil gas is drawn in through the many cracks andpenetrations of the floor slab. Space heat, when it is neededis supplied by a heat pump cycle through the air conditioningductwork. In the summertime when it is warm and humidoutdoors, the negative pressure in the building draws air inthrough the cracks and holes in the building shell. As the airgets closer to the cool interior, the relative humidity in-creases, and the risk of condensation in the building shellnear the interior sheetrock increases.

Pressurizing the house would reduce both the soil gasentry and the chance of condensation occurring. This couldbe accomplished by planning the ductwork so that it could beeasily sealed to reduce losses, running a more extensivereturn air sysiem, and using dampers so more air is suppliedto the house than is exhausted. The difference betweensupply ande^Schaust will be lost through the building shell.By making the building shell as airtight as possible, theamouni of air it takes to do this will be smaller. If more airis supplied to the building than is removed by the return airduels ihen the difference must come ihrough leaks in thereturn air ductwork. It is possible that an outdoor air supplyduct will have lo be run to the return air side of the airhandler to make ihe pressurizaiion (and coincidenially venu-laiion) air available. The incoming air musi be cooled downlo house lemperature resulting in a sensible and latcni heatgain energy penalty. In ihis case two approaches could bemade to reducing the cooling energy penalty. A high effi-ciency cooling coil using dchumidifying heat pipe technol-ogy could be used to precondition the incoming air. Second,a heat pump domestic hot water heater could be used to pre-cool the incoming air and heat the hot water at the sametime.

The bathroom, laundry and kitchen exhausts would haveto operate as normally installed and enough pressurizaiion airwould have to be added so thai ihe intermittent operation ofthese exhausts would not overcome the lime averaged ben-efits of house pressurizaiion.

Combustion products are probably not an issue becausethere is no combustion device in the house.

Summarizing ihe system :

• Pressurize the house using ihe air handlingsysicm (concurrently adding ventilation air)

• Reduce the cooling load penalty bypreconditioning the incoming air ( reduc ingthe indoor humidily and/or healing ihe domestichot water)

6.5 ConclusionsIt is obvious that an approach in new construction that

matches mechanical system design and installation to themultiple needs of occupant health, safety, and comfort and tobuilding longevity requires an understanding of how iheclimate and building interact. This approach is both morecomprehensive in effect and complex in design and installa-tion than the other techniques outlined in this manual. Thisline of attack should only be pursued by qualified peoplewho have training and experience in mechanical systems,because it is too easy to overlook an important aspect of theinterconnections involved. In many ways it is a more sophis-ticated control strategy than soil depressurizaiion or me-chanical barriers.

37

References

ACI - American Concrete institute. Detroit, MIACI332R-84 - Guide to Residential Cast in Place Concrete

ConstructionACI302.1R-80 - Guide for Concrete Floor and Slab

Coinforced Concrete ConstructionACI212.1R-81 - Admixtures for ConcreteACI544 - State of the Art Report on Fiber-Reinforced

Concrete ConstructionAk86 - Akerblom, G., Investigation and Mapping of Radon

Risk Areas, International Symposium on GeologicalMapping in the Service of Environmental Planning,Trondheim, Norway, May 6-9, 1986.

ASHRAE85 - American Society of Heating, Refridgeration,and Air Conditioning Engineers, 1985 FundamentalsHandbook, Atlanta, GA

Br86 - Brennan, T., and W. Turner. Defeating Radon, SolarAge, p. 34, March 1986.

CABO86 - CABO One and Two Family Dwelling Code/1986, Council of American Building Officials, FailsChurch. VA. 1986.

CMHC84 - Scanada Consultants Ltd., The ThermalPerformance of Furnace Rues in Houses, CanadaMortgage and Housing Corporation, Ottawa. Canada,1984.

Da86 - D'Alesandro, W., Foundation Drainage Mats,Progressive Builder, 11:10, pp. 1 2 - 1 3 , September1986.

EPA87 -U.S. Environmental Protection Agency, Removal ofRadon from Household Water. OPA-87-011. September1987.

ERDA85 - Niischke, I.A.. G.W. Traynor, J.B. Wadach, M.E.Garkin, and W.A. Clarke, Indoor Air Quality, Infiltrationand Ventilation in Residential Buildings, NYSERDAReport 85-10. March 1985.

FL88 - Proposed Interim Guidelines for Radon ResistantConstruction, Tallahassee, FL, March 1988.

Har88 - Harris, D.B.. J.S. Ruppersberger, and M. Wakon,Radon Wall Coalings Test Facility Design andDevelopment Phase, in Proceedings: The 1988Symposium on Radon and Radon Reduction Technology,Vol. 2, EPA-600#-89-006b (NTIS PB89-167498), March1989.

Hu88- Hubbard, L.M., B. Bolker, R.H. Socolow, D.Dickerhoff, and R.B. Mosley, Radon Dynamics in aHouse Heated Alternately By Forced Air and by ElectricResistance, in Proceedings: The 1988 Symposium on

Radon and Radon Reduction Technology, Vol. 1, EPA-600/9-89-006a (NTIS PB89-167480), March 1989.

Ku88 - Kunz, C, C.A. Laymon, and C. Parker, GravellySoils and Indoor Radon, in Proceedings: The 1988Symposium on Radon and Radon Reduction Technology,Vol. 1, EPA-600/9-89-006a (NTIS PB89-167480), March1989.

Ma87 - Matthews, T.G., et al., Investigation of Radon Entryand Effectiveness of Mitigation Measures in SevenHouses in New Jersey : Midproject Report, Oak RidgeNational Laboratory, Report ORNL/TM-10671,December 1987.

Mu88 - Muessig. K.W., Correlation of Airborne RadiometricData and Geologic Sources with Elevated Indoor Radonin New Jersey, in Proceedings: The 1988 Symposium onRadon and Radon Reduction Technology. Vol. 1, EPA-600/9-89-006a (NTIS PB89-167480). March 1989.

Mur88 - Murane, D. U.S. Environmental Protection Agency,Office of Radiation Programs, Washington, D.C. personalcommunication, June, 1988.

Na87 - Nagda. N. L., Florida Statewide Radiation Study,GEOMET Technologies, Inc., Report IE-1808,November 1987.

NCMA - National Concrete Masonry Association, Hemdon,VA

NCMA68 - Specification for the Design and Construction ofLoad Bearing Concrete Masonry, 1968.

NCMA71 - Reinforced Concrete Masonry Design, 1971.NCMA72 - Concrete Masonry Foundation Walls NCMA-

TEK 43. 1972.NCMA87- Radon Safe Basement Construction NCMA-TEK

160A, 1987.Ne88 - Nelson, G., Finding the Raws, Energy Design

Update, Cutters Information Corporation. February 1987.NFoPA88 - Radon Reduction in Wood Roor and Wood

Foundation Systems, National Forest ProductsAssociation. 1988.

NFPA - National Fire Protection Association, Quincy, MANFPA1 - Fire Protection Code, 1987.NFPA54 - National Fuel Gas Code, 1984.NFPA70 - National Electric Code, 1981.

Ni89 - Niischke, I., Radon Reduction and Radon ResistantConstruction Demonstrations in New York, U.S.Environmental Protection Agency, EPA/600/8-89/001(NTIS PB89-151476), January 1989.

39

ORNL88 - Oak Ridge National Laboratory. BuildingFoundation Design Handbook, Oak Ridge, TN, 1988.

Os87a - Osbome, M.C., Resolving the Radon Problem inClinton, New Jersey, Houses in. Indoor Air '87:Proceedings of the 4thlnternational Conference OnIndoor Air Quality and Climate, Vol. 2, pp. 305-309,Berlin, West Germany, August 1987.

Os87b - Osbome, M.C., T. Brennan, and L.P. Michaels,Monitoring Radon Reduction in Clinton, New Jersey,Houses, presented at the 80ih APCA Annual Meeting,

New York, NY, June 1987.Os87c - Osbome, M.C., Four Common Diagnostic Problems

That Inhibit Radon Mitigation, JAPCA, 37: 5. pp. 604 -606, May 1987.

Pe87 - Peake, T., EPA Office of Radiation Programs,unpublished data, November 1987.

Pu88 - Pugh, T.D., Literature Search: Radon ResistantConstruction, Institute for Building Sciences, FloridaA&M University, Tallahassee, FL, January 1988.

Py88 - Pyles, M., Pennsylvania Department ofEnvironmental Resources, Harrisburg, PA, personalcommunication, April 22, 1988.

Ru88 - Rugg. M., House Age, Substructure and HeatingSystem : Relationships to Indoor Radon Concentrations,

in Proceedings : The 1988 Symposium on Radon andRadon Reduction Technology, Vol. 2, EPA-600/9-89-006b (NT1S PB89-167498), March 1989.

Sc87 - Scott, A.G., and W.O. Findley, Production of RadonResistant Foundations, American ATCON, Inc.,September 1987.

Se89 - Sextro, R.G., W.W. Nazaroff, and B.H. Turk, Spatialand Temporal Variation in Factors Governing the RadonSource Potential of Soil, in Proceedings: The 1988Symposium on Radon and Radon Reduction Technology,Vol. 1, EPA- 600/9-89-0063 (NTIS PB89-167480). March1989.

Si90 - Siniscalchi, M.S., L.M. Rothney, B.F. Toal, M.A.Thomas, D.R. Brown, M.C. van der Werff, and C.J.Dupuy, Radon Exposure in Connecticut: Analysis ofThree Statewide Surveys of Nearly One Percent of SingleFamily Homes, presented at the 1990 InternationalSymposium on Radon and Radon Reduction Technology,Atlanta, GA, February 1990.

Sw82 - Translation of Statens planverk. report 59, 1982 -Stockholm, Sweden, p. 3.

To88 - Tooley, J.J., Mechanical Air Distribution aUrfInteracting Relationships, Natural Florida Retrofit, Inc.,1988.

40

Appendix A

Current Radon-resistant New ConstructionResearch Efforts

There are several U.S. EPA, AEERL radon-resisiantresearch projects that are ongoing or recently completed.Some of these are in cooperation with other research agencies,for example the New York State Energy Research and De-velopment Authority and the U.S. EPA jointly pursued aresearch effort involving 15 newly constructed houses withradon-resistant features and 5 control houses.

The lack of a reliable method to estimate indoor radonconcentrations in a new house before it is built makes theresults of radon-resistant new construction research difficultto interpret. Without pre-test data, how can a new house witha successful radon control method be distinguished from the9 out of 10 new houses that are below the EPA ActionGuideline of 4 pCi/L ? Several approaches have been madeto develop confidence in the results of projects. They are :

1) Make measurements in a large number ofexperimental and control houses so reliabilitycan be estimated using statistical methods.

2) Build the test houses in neighborhoods known

to have elevated indoor radon levels in a largefraction of the exist ing houses. In someneighborhoods >50% of the houses are over 4pCi/L.

3) Study a small number of new buildings withradon control features in detail. Phase the studyto separate the radon control features andestablish how effective they are. For example,a soil depressurization method can be tested bymonitoring indoor radon with the vent stackopen and the blower off, with the vent stackopen and the blower on, and with the vent suckblocked off. Tracer gases can be used to test theeffectiveness of mechanical barriers or theamount of airflow through a soil dcprcssurizauonsystem that comes from inside the basement.

Lastly, and as it seems to be turning out, if buildingswith radon-resistant new construction features end up havingelevated indoor radon concentrations, then the features didn'twork well enough. There is no way to tell if the featureswere partially successful and the elevated indoor radon wouldhave been higher yet had they not been used.

Table A1. Current EPA/AEERL Radon-realatanl New Construction Projects.Walla Site Method* Tasted

Pro|eet

EPA1b

NYSEROA

Block

0

15

Pour Char.

10

0 Highly

Barrier

10

8

PaM.SSD

10

8

Act.SSO Coi

5

8 coperm.

controlhou as (NY)averaged34 4 pCi/L

NAHB-NRC(NJ)

EPA2(VA/PA)

4

0

6

4

Highlyvaried

2 day2 perm.

0

4

0

4

0

4 % indoor arin exhaustestimated

• EPAlb - Pauive and Active Soil DepreMurization• NYSEROA (NY) - Barrier/ActiveXas«ive• NAHB-NRC (NJ) - Passive and Active Soil Depressurization• EPA2 (VA/PA) - Barrier/Active/Passive/Energy Penalty

41

Table A2. Preliminary Results from Currant EPA Research Projectt.Average Basement Radon (pCI/L)

Project Barrier Passive Active * of Houses

EPA16 145 60 <1 10NYSERDA (NY) 158 133 28 15EPA2 (PA) 1 3 07 1 1 2EPA2 (VA) 1 4 7.0 1 1 1

EPA16 - Passive and Active Soil DepressunzattonNYSERDA (NY) - Barner/Active/PassiveEPA2 (VA/PA) • Barner'ActivePassive/Energy Penalty

It should be kept in mind that the results of these researchprojects are preliminary. However, it is clear that in all theprojects at least some of the buildings that had radon resistantfeatures built in also ended up with elevated radon levels.Whether this is the result of failure of the systems at con-ceptual, design or installation levels is unknown at this point.

42

Appendix B

Other Radon-resistant New ConstructionGuidelines

Several other groups are currently working on or havealready issued guidelines to control radon in new buildings.These groups are usually either Professional or Trade Asso-ciations or government agencies.

There are thousands of local, state and national codesjurisdictions in the United States. It is their job to enforceexisting codes. Many legal, enforceable codes are based onmodel codes that have been developed by model codes asso-ciations. The model codes often reference standard practiceas recommended by industry associations.

Developed and A vailable:DOE, Oak Ridge National Laboratories. ORNL/Sub/86-

72143/1, "Building Foundation Handbook," 1988. An im-pressive publication that addresses nearly all imaginable as-pects of foundation design and construction. Chapter 10 isdevoted to radon control in new construction.

National Forest Products Association. "Radon ReductionIn Wood Floor and Wood Foundation Systems," 1988 - A20-page booklet describing radon control strategies for per-manent wood foundations. National Forest Products Asso-ciation is a trade association for the producers of woodproducts.

U.S. EPA, Office of Radiation Protection - NationalAssociation of Homebuilders Research Foundation, "RadonResistant New Construction - An Interim Guide," August1987, OPA-87-009 - A 10-page pamphlet that covers funda-mentals and recommendations.

In Process, Not Yet Available :American Society for Testing and Materials (ASTNf),

"DRAFT-Standard Guide for Radon Control Options ForNew Home Construction, "White Paper," - Currently in pro-cess. ASTM is an organization composed of users, producersand interested parties who work together via a consensusprocess to produce voluntary industry guidelines. All publi-cations go through extensive peer review. This document isbeing developed by Committee E-06.41.08, Reduction ofRadon Intrusion Into Buildings. Contact Bion Howard at theNational Association of Homebuilders Research Center, 400Prince George Blvd., Upper Marlboro, MD 20772. Ph. (301)249^000.

Florida - The State Legislature mandated in 1988 (hatthe Florida University system develop a model building codefor radon control methods in new and existing buildings. Thepreliminary planning has occurred for this effort. ContactThomas Pugh at the Florida A & M University School ofArchitecture, Tallahassee, FL 32308. Ph. (904) 599-3000.

U.S. EPA, Office of Radiation Programs - Currentlymandated by Federal legislation to develop a model code forradon resistant new construction, ORP is in the process ofwriting a draft of a radon resistant new construction code.Contact Dave Murane, U.S. EPA, ORP, 401 M St. S.W.,Washington. DC 20460. Ph. (202) 475-9623.

Washington Energy Extension Service, "Northwest RadonOrdinance" - In process. This is a model radon resistant newconstruction code being developed by the Washington EnergyExtension Service with extensive review by interested parties.Contact Mike Nuess, WEES, N. 1212 Washington St., Spo-kane, WA 99201. Ph. (509) 456-6150.

43 in. S GOVERNMENT PRIMING OFFICE: l • '«-600/4JO-n