radon remediation and prevention in new construction

SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN

RADIATION AND NUCLEAR SAFETY AUTHORITY

Radon remediation and prevention in new construction

Olli HolmgrenSTUK - Radiation and nuclear safety authority

Finland

Tallinn May 3 - 4, 2016



Outline

• Radon prevention

– Building code and guidelines in Finland

– Radon prevention methods used in Finland

• Radon remediation methods

• RADPAR recommendations and Conclusions

May 3-4, 2016 2Olli Holmgren



Radon in the National Building Code of Finland• The National Building Code contains technical regulations and

instructions, which are given by decree (Ministry of the Environment)

– The regulations are binding, and concern the construction of new buildings.

– The regulations are applicable to renovation and alteration works only insofar as the type and extent of the measures and a possible change in use of the building require.

– The instructions are not binding but present acceptable solutions.

• Regulations related to radon in two parts

– B3 Foundations

– D2 Ventilation and indoor climate




Building codeVentilation and indoor climate

• Building shall be designed and constructed such that there is no gases, particles ... in indoor air that could cause health detriment/risk (very unofficial translation)

• Radon reference value of 200 Bq/m3 (annual average)

• Guideline value for design (maximum acceptable value)

• Radon included for the first time in 1987

– No big effect




Building code, Foundations

– Regulation: In the design and construction work, radon risks at the construction site shall be taken into account

– Instructions/guideline

• The limit value of 200 Bq/m3, which is the design guideline value, is generally exceeded in the most part of Finland, if no countermeasures are taken.

• A radon-technical design may be left out only in case the local radon surveys clearly show that the radon concentration inside residential buildings is consistently below the permitted maximum value.

• If radon is not taken into account in the design, written grounds for that shall be attached to the design documents of the building project.

• The original soil and soil brought elsewhere to the site for land filling, as well as drainage gravel, always have an impact on the risk of radon in the building ground. A filled thick gravel layer may indoors alone produce radon concentrations exceeding the limit value.

• The radon concentration inside a building can be significantly influenced by the selection of base floor structures and foundation method.

• Written statement if radon prevention is not applied




Building code, Foundations

• In practice

– Radon-technical details in the design documents are required by the building authority in municipalities, especially in high radon areas

– The installation of radon preventive measures is not controlled

– Radon measurement is not required in the building code

• Some local authorities require/recommend Radon measurement

– If radon level > 200 Bq/m3, constructors mitigate as a part of warranty




Follow up of new construction

• Measurements in national radon database

– Approximately 10 000 measurements / year

– Only a part of new houses are measured

– Radon measurement should be made obligatory as a part of building permission process

• Random sample survey in 2009 by STUK

– Representative results for the whole country

=> Development of guidelines and practices, training




Guide for radon prevention

• Guide for radon prevention was revised in 2003

– Use of a strip of bitumen felt for sealing and installation of radon piping(network of perforated pipes beneath the floor slab)

– Resulted from the national research project

• Co-operation of STUK, Universities, companies

– Published by Building Information Ltd (Rakennustieto Oy)

– Replaced the first guide published in 1993 by the Ministry of Environment

• Developed by Helsinki University of Technology

• Funding: Ministry of environment and Ministry of Social Affairs and Health

– Updated in 2012 by STUK and Building Information Ltd




Radon prevention in Finland

– Selection of foundation and base floor with typically low radon levels

– Crawl space, monolithic slab foundation

– If separate foundation wall and slab on ground is used

– Sealing with strip of bitumen felt

– Installation of radon piping (a network of perforated pipes beneath the floor slab)

• Sealing of pipe penetrations




Foundation and base floor types, FIN


Slab on groundPrevalence 2006: 64%High radon levels (mean 96 Bq/m3)

Crawl-space, suspended floorPrevalence 2006: 19%Low radon levels (mean 44 Bq/m3)

Monolithic slabPrevalence 2006: 1%Low radon levels (mean 38 Bq/m3)

Semi-basement and basementPrevalence 2006: 16%High radon (mean 151 Bq/m3)



Entry routes in typical Finnish houses

Slab on ground

• Gap between foundation wall and floor slab

• Permeable lightweight aggregate concrete blocks

• Non-sealed pipe penetrations

Basement or semi-basement

• Light-weight aggregate concrete blocks and hollow-block walls incontact with soil




Radon resistant new constructionguideline

Sealing of joint between slab and foundation wall,

and walls in contact with soil

Polyesther-reinforced bitumen felt

• cast in direct contact with bitumen felt at least 15 cm

Figures from Guide RT 81-11099

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Installation of the bitumen felt

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Figures from Guide RT 38056 (Katepal Oy)

May 3-4, 2016

Olli Holmgren



Example of successful sealing workBitumen felt before casting of floor slab

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Radon resistant new constructionguideline

• Installation of a passive piping system: discharge open above roof

Network of perforated drainage pipe installed below the floor slab

If radon concentration> 200 Bq/m3,

install a radon fan

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Olli Holmgren



Installation of radon piping


Figure from Guide RT 81-11099



Multi-branch radon piping


1. Suction pipe (perforated drainage pipe)- end of the pipe closed

2. Collector pipe3. Exhaust duct

Figures from Guide RT 81-11099



New-construction survey 2009

• Aim: study the effect of new regulations and guidance

• Original sample 3000 dwellings, randomly chosen

– Building permission given in 2006

– Notice of removal before November 2008(=> Houses completed in 2006 – 2009)

– 13% of dwellings in low-rise houses that received building permission in 2006 (single family houses, semi-detached houses, terraced houses)

• Radon concentration measured in 1561 dwellings

– Final participation rate 52 %

– Two months measurements in March - May 2009

– Average radon concentration 95 Bq/m3, median 58 Bq/m3

Ref. Arvela H, Holmgren O, Reisbacka H. Radon prevention in new construction in Finland: a nationwide sample survey in 2009. Radiation Protection Dosimetry vol. 148, pp. 465-474, 2012 .




Results, Foundation and radon

Lowest concentrations

• Houses with crawl space, median 29 Bq/m3

• Houses with a monolithic floor slab, median 27 Bq/m3

Highest concentrations

• Houses with semi-basement and basement, average 161 Bq/m3, median 97 Bq/m3

• Main reason: defective measures for radon prevention in the block walls in contact with soil

Separate foundation wall and slab on ground

• Remarkable progress in radon prevention,average 97 Bq/m3, median 68 Bq/m3

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May 3-4, 2016



Olli Holmgren

Results• Preventive measures were taken

- in 92 % of houses in six provinces with highest radon

concentration (Area 1)

- in 38 % of houses elsewhere in the country (Area 2)

- in 54 % of houses, whole country

Radon concentrations and radon reduction compared with houses completed in 2000-2005 (sample survey 2006)

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New constructionsurvey (2009)

Sample survey(2006)

Radon reduction

Area 1 125 (Bq/m3) 237 (Bq/m3) 47%

Area 2 83 (Bq/m3) 112 (Bq/m3) 26%

Whole country 95 (Bq/m3) 142 (Bq/m3) 33%

May 3-4, 2016



Olli Holmgren

Results• Preventive measures were taken

- in 92 % of houses in six provinces with highest radon

concentration (Area 1)

- in 38 % of houses elsewhere in the country (Area 2)

- in 54 % of houses, whole country

•Percentage exceeding 200 Bq/m3 and 400 Bq/m3

- 200 Bq/m3 10.6% sample survey (2006) 15.8%

- 400 Bq/m3 2.1% 3.8%

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RADIATION AND NUCLEAR SAFETY AUTHORITY Olli Holmgren

May 3-4, 2016

Radon concentration grouped by construction yearResults of 1949 – 2005 are based on the nationwide sample survey 2006 (STUK-A242, Mäkeläinen et al. 2009).

The last bar (2006-2008) represents the results of the new construction study (2009).

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Decreasingtrend



Effect of preventive measures

• Studied using regression analysis

– comparison of houses with and without preventive measures

• Radon reduction

– passive radon piping and sealing with a strip of bitumen felt 57%

– passive radon piping without sealing 41%

Ref. Arvela H, Holmgren O, Reisbacka H. Radon prevention in new construction in Finland: a nationwide sample survey in 2009. Radiation Protection Dosimetry vol. 148, pp. 465-474, 2012 .

• Passive radon piping extracts also moisture from the ground below the house

• Prevention of other impurities of the ground?




Challenges

• Widespread and skilled implementation of preventive measures throughout the country

• Lightweight aggregate concrete block walls in contact with soil

• Houses build on crushed rock

• Sealing of pipe penetrations

As a summary, both sealing and passive piping are needed

• Education

– Designers and constructors

– Building authority officers




Radon remediation

• Radon sump or sub-slab depressurisation

• Radon well

• Improving ventilation

• Sealing



Sub-slab depressurization (SSD)or radon sump

• Active SSD: forced ventilation using an exhaust fan

– Best radon remediation method

• Passive SSD: natural ventilation due to stack and wind effects



RADIATION AND NUCLEAR SAFETY AUTHORITY 27May 3-4, 2016

Radon sump

• creates under-pressure under the floor slab

• lowers the soil air radon concentration

Olli Holmgren



Optimum position for suction pit

Center of the house

- exhaus duct can be hidden in the closet

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Load-bearing partition

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Radon sump with two suction pits

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Example, suction pipes drilled from cellar

Martin Jiránek, “Radon remedial and protective measures in the Czech Republic” Czech Technical University, Praha, Czech Repuplic

Typical efficiency 70 - 98 %.

Olli Holmgren


RADIATION AND NUCLEAR SAFETY AUTHORITY Olli Holmgren 32May 3-4, 2016

Radon well• Effective only when soil is permeable enough, on gravel and coarse sand.

• Decreases soil gas radon concentration in a large soil volume



Geography - gravel deposits - eskers

Landscape features were created by meltwater gravel deposit

Major esker formations in Finland

Radon concentrations are high esp. in eskers in wide areas in the southern Finland.



Radon well

• Typical efficiency 70-90%

• Applicable to single family houses, row houses and big industrial buildings

• Effective up to 30 meters (50 m)

• Fan power 150 W - 300 W, single family house - big buildings

• Depth 3-5 meters

• In many difficult cases on deep coarse soils more efficient than SSD



Radon well• Exhaust stack can be positioned also far from the house.

• Exhaust fan may alternatively be inside the stack.

• In cold climate thermal insulation necessary.



Example Hollola

Play ground in the yard

• 4 row houses (buildings)

• 20 dwellings

• 2 radon wells

• Before radon remediation110 - 2350 Bq/m³

• After: 20 - 420 Bq/m³

Olli Holmgren



Hollola

Olli Holmgren



Improving ventilation

• Can be effective if the initial state of the house ventilation is poor or if the negative pressure is high

• Possible actions in living spaces

– Opening or adding supply air vents

– Increasing air exchange of the mechanical ventilation system

– It is important not to increase negative pressure

0

100

200

300

400

500

0 0,5 1 1,5

Rad

on

co

nce

ntr

atio

n (

Bq

/m3

)

Air change / hour

Ventilation and radon

Nominal design valuein new houses




Ventilation and negative pressure

• Optimal ventilation system and negative pressure depend on the air tightness of the house envelope

– Infiltration

• REHVA - Federation of European Heating, Ventilation and Air Conditioning Assosiation

– www.rehva.eu

39Olli Holmgren

May 3-4, 2016

http://www.rehva.eu/



Mechanical ventilation increases underpressureand radon inflow

Good news: building code requires use of supply and exhaust ventilation due to energy savings

Ventilation strategy Typical heating season underpressure, Pa

Natural 1-2

Mechanical exhaust 7-10

Mechanical supply and exhaust, (heat recovery)

2-5

Olli Holmgren



Cellars and crawl-spaces

• Improving ventilation in cellar or in crawl space have been used to reduce radon levels in living spaces

• Sealing of the intermediate floor and staircase between cellar and living spaces

• Pressure differences between cellar and living spaces

• Ventilation of crawl space

– Natural or mechanical

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May 3-4, 2016

http://twiecki.github.io/blog/2014/03/17/bayesian-glms-3/



Sealing entry routes

• Typical entry routes from the ground

– cracks, gaps, holes and pipe penetrations in the floor slab and in the walls in contact with soil

• Complete sealing often very demanding depending on the structures of the house

– Depends on the structures: timber vs. concrete structures

• Easier in new construction than in old houses

Figure. Typical entry routes for slab on ground and separate foundation wall made of light-weight aggregate concrete blocks




Sealing pipe penetrations

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May 3-4, 2016

Efficiency of radon remediation methods in FINQuestionnaire study in 2012, 496 dwellings

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-40 -20 0 20 40 60 80 100

Radonpitoisuuden alenema (%)

Yhdistelmät (201)

Muut yksittäiset menetelmät (50)

Rakenteiden tiivistäminen (17)

IV:n parantaminen asuintiloissa (63)

Radonkaivo (13)

Radonimuri (39)

Radonputkiston aktivoiminen (113)

Min 25. percentile 75. percentile

Median Max

Radon reduction (%)

Activation of radon piping (113)

Sub-slab depressurisation (39)

Radon well (13)

Improving ventilation (63)

Sealing (17)

Other methods (50)

Combinations (201)

Olli Holmgren



Efficiency of radon remediation methods in Finland• Sub slab depressurization and radon well most efficient techniques

– Efficiency typ. 65–90%

• Improving ventilation and sealing less effective

– Efficiency typ. <50%

• Complete sealing is difficult

– Lightweight aggregate concrete blocks

– Fixed pieces of furniture

– Wooden frame that most of the Finnish houses have

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RADPAR recommendations and Conclusions



RADPAR project

• Radon prevention and remediation (RADPAR)

• Three years project, 5/2009 – 5/2012

• Funding from the European Union in the framework of the Health Programme (DG SANCO)

• Partners from 14 countries

– 11 Associate Partners

– 7 Collaborative Partners

• Website: web.jrc.ec.europa.eu/radpar/

• General objective: to assist in reducing the significant public health burden of radon related lung cancers in EU Member States


http://web.jrc.ec.europa.eu/radpar/index.cfm



RADPAR Work packages

WP 1: Coordination of the project

WP 2: Dissemination of the results

WP 3: Evaluation of the project

WP 4: Developing policies and strategies to promote effective radon prevention and remediation

WP 5: Establishment of an EU radon risk communication network

WP 6: Assessment and harmonization of radon control technologies in Member States

WP 7: Analyses of cost-effectiveness and health benefits of radon control strategies




RADPAR recommendations for radon prevention• The following general recommendations are given for prevention of

radon ingress from soil.

• In the application of these recommendations, national conditions and local geogenic radon potential (soil permeability and soil air radon concentration) should be taken into account.




RADPAR recommendations for radon prevention• The techniques of radon prevention in new construction should be

established in national building codes, regulations and guidelines.

– The technical means recommended for new construction depend on building, foundation and soil characteristics.

– Alternative approaches are the use of radon control options in all new homes (WHO 2009) or to define more strict requirements for radon-prone areas.

• Integration of radon prevention in new construction needs to done at early stage of building design.

• Most radon-resistant foundation types are recommended

– For example, crawl space/suspended floor or monolithic concrete slab




Examples of foundation and base floor types

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Figure 2. Typical entry routes in Finland for slab on ground and separate foundation wall made of light-weight aggregate concrete blocks

Figure 1. Typical entry routes in Austria for new houses. Thick concrete plate as a foundation and base floor.

www.radon-info.de



RADPAR recommendations for radon prevention• The base floor should be sealed as air tight as possible.

• The pipe penetrations and service entries should be sealed.

• In countries, where continuous waterproof or damp-proof courses are common part of building substructures, these courses should act also as efficient radon barriers.

• In houses with slab on ground, installation of a passive sub-slab depressurization system is recommended

– radon piping or sump with exhaust duct open above roof

• In houses with basement/cellar or semi-basement, walls in contact with soil should be air tight.

– This is very demanding and it should be done extra carefully if the walls are made of permeable lightweight concrete blocks.




Execution of radon-proof courses

Example from UK – application of a polymeric membrane

By: Chris Scivyer, BRE, UK By: Martin Jiranek, CTU, Czech Republic

May 3-4, 2016

Olli Holmgren

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RADPAR recommendations for radon remediation• The level and type of remediation works to be undertaken depends on the

initial level of indoor radon and characteristics of considered building.

• The best results have been achieved using active methods like sub-slab depressurization and radon well.

– This approach maximizes radon reduction with a small incremental cost difference compared to other, more limited approaches. Furthermore, more forceful approaches give greater confidence in achieving radon reduction targets.

• Where applicable, improving ventilation of the cellar or improving ventilation of the crawl space can be an efficient method to reduce radon concentration in living spaces.

• The ventilation of the living spaces should always be checked. Poor ventilation increases radon concentration. An air exchange rate of 0.5 to 1 1/h is generally recommended in national regulations.




Conclusions, prevention

• New radon regulation in the Finnish building code for foundations (set in 2004) increased considerable the number of houses protected against radon

– Local building authority requires radon prevention in the building permission, especially in radon-prone areas

– Detailed guideline for designing radon preventive measures in new construction

– Radon concentrations reduced 33 % in whole Finland, 47 % in provinces of highest concentration compared to houses build in 2000 - 2005

• STUK recommendations: Radon prevention in all new buildings

– Effective way to reduce the average radon concentration of the population, reduction of low radon levels as well

• Radon should be measured after the construction is finished

– If radon level > 200 Bq/m3, mitigation under warranty




Conclusions, remediation

• All remedial actions should aim at radon levels well below the reference level

– Radon sump should be primary remediation method

– Improving ventilation of the cellar or the crawl space can be efficient

• Sealing has been used with good results in work places(usually concrete structures)

• Unique national characteristics of construction practices must be taken into account

– Foundation, cellar, base floor




Thank you!

Contact information:

Olli Holmgren

olli.holmgren(at)stuk.fi

www.stuk.fi, www.radon.fi

p. +358 9 75 98 85 55

Laippatie 4, P.O.Box 14

FI-00881 Helsinki

Finland


http://www.stuk.fi/

http://www.radon.fi/

radon remediation and prevention in new construction

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