radon remedial measures - kps.fsv.cvut.cz

IAEAInternational Atomic Energy Agency

RADON REMEDIAL MEASURES

CORRECTIVE ACTIONS FOR EXISTING BUILDINGS

Martin JiránekCZECH TECHNICAL UNIVERSITYFaculty of Civil EngineeringDepartment of Building StructuresThákurova 7, 166 29 Praha 6E-mail: [email protected]

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CONTENT

1. Purpose of corrective actions2. Factors influencing the design3. Principles of corrective actions4. Rules for selecting corrective actions5. Sealing of radon entry routes6. Ensuring air-tightness of the substructure7. Sub-slab depressurization8. Air gap depressurization9. Measures for houses on crawl spaces/cellars10. Ventilation measures11. Measures against radon from building materials12. Thermal retrofitting and indoor radon

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1. PURPOSE OF CORRECTIVE ACTIONS

The purpose of radon corrective actions is to ensure that radon concentration in every room of the habitable space decreases below the reference level or design value.

Reference level is prescribed by legislation within the range 100 – 300 Bq/m3.

Design value is prescribed by the owner (determined for example on the basis of ALARA principle).

Fulfilment of this objective is verified by measurement of radon concentration under the ventilation rate satisfying the minimum hygiene requirements.

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2. FACTORS INFLUENCING THE DESIGN

CORRECTIVE ACTIONS

Results of diagnostic

measurements

Existing conditionof the building

Climatic conditions

Applicability of the measure

Workmanship, experience of the contractor

Effectiveness of the measure

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The goal is to determine the sources of radon and gamma radiation, and the way that radon spreads throughout the building.

Examples of suitable diagnostic measurements are: • Determining the average radon concentrations in all rooms in the

floor in contact with the ground

• Determining the continual courses of radon concentrations

• Measurement of radon concentration in air samples taken from possible radon entry points

• Measurement of radon concentration in the soil and soil permeability around and under the building

• Determining the gamma dose rate

• Determining the radon concentration in the supply water

2.1 Results of diagnostic measurements

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2.2 Existing condition of the building

The goal of the building survey is to prepare a basis for the design of applicable and effective corrective actions with minimum negative impact on the house construction.

Building survey should focus on: • Location of habitable and non-habitable rooms;• Airtightness of the building envelope;• Predominant type of the building material;• Method of ventilation;• Defects and failures of the structure;• Condition and composition of structures in contact with the

soil (cracks, humidity, air-tightness of pipe penetrations, presence of installation channels and ducts).

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2.3 Climatic conditions

Climatic conditions (average annual wind speed, typical thickness of snow cover, temperature differences, amount of rainfall, etc.) influence the design of corrective actions as follows:

• Location of outlets of ventilation pipes;• Applicability of ventilation systems (natural x mechanical,

balanced systems x overpressurization);• Problems with condensation of water vapour (inside

ventilation pipes or on their surface, inside the building envelope, etc.).

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2.4 Effectiveness of corrective actions

Effectiveness (%)Corrective actionTypical range Max

New floors with radon-proof insulation 35 - 45 50

New floors with radon-proof insulation + passive sub-slab or floor air gap ventilation 45 - 55 60

New floors with radon-proof insulation + active sub-slab or floor air gap depressurization 80 - 90 95

Active sub-slab depressurization installed without the floor reconstruction 80 - 95 99

Sealing of radon entry points (cracks, pipe penetrations, etc.) 10 - 40 60

Increased natural ventilation of the habitable space 20 - 40 50

Improving ventilation rate by mechanical ventilation 50 - 70 75

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3.1 Sealing of radon entry routes

This method is often used in combination with other methods.

Effectiveness is usually lower than 40 %!

Sealing is usually applied for:• cracks in contact structures• services penetrations• gaps between walls and floors

3. PRINCIPLES OF CORRECTIVE ACTIONS

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3.2 Ensuring air-tightness of the substructure

Effectiveness is usually lower than 45 %!

It is usually not possible to place radon barrier material continuously over the entire surfaces of walls and floors in contact with the soil

Use only if the reconstruction of floors is necessary due to their bad technical condition.

It is recommended to use this measure in combination with sub-slab or air gap depressurization!


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3.3 Creating underpressure in the subsoil

Effectiveness is around 95 %.

Can be ensured by:• radon sumps• drilled tubes• perforated pipes• radon well

The preference should be given to systems that can be installed without the reconstruction of floors.


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3.4 Creating overpressure in the subsoil

Known also as air cushion method.

The principle is that indoor air is forced in the sub-floor region, in order to dilute radon concentration under the building.

Used rarely, when sub-slab depressurization is not effective.

Effectiveness can be as high as 85 - 95 %.

From UK and USA experience this works best in highly permeable soils.CTU

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3.5 Creating underpressure in the air gaps formed over the contact structures

Effectiveness is around 90 %.

The gap can be formed also along walls made of uranium rich materials. In this case the method serves for removing radon exhaled from the wall.

Suitable also for radon from building materials!


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3.6 Increasing ventilation rate of the habitable space

Can be ensured by:• improving natural

ventilation

• installation of hybrid or mechanical ventilation

Effectiveness is usually lower than 40% (natural

ventilation) or 70% (mechanical ventilation).

Suitable not only for radon from the soil, but also for radon from building materials!


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3.7 Increasing ventilation rate of crawl spaces or non-habitable spaces

Can be ensured by:

• improving natural ventilation

• installation of mechanical ventilation

Effectiveness is usually around 50% (natural ventilation) or 75% (mechanical ventilation).

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• Measure must have sufficient efficiency according to the measured radon concentration

• It must be easily applicable• It should not worsen the technical state and the quality of

the building• It should not disturb the occupants by higher noise levels

and other adverse effects• Operating costs must be at a reasonable level (it should

not induce large thermal losses)• It is advantageous, if other problems and defects of the

building are solved together with radon

4. RULES FOR SELECTING ACTIONS

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• sealing of radon entry routes (cracks, pipe penetrations, etc.)

• improving the cellar/crawl space – outdoor ventilation

• preventing the air movement from the cellar/crawl space into the first floor

• improving the indoor – outdoor (natural) ventilation• creating a slight overpressure within the building (not

applicable in countries with cold climates)

Measures applied in case of just above the reference level (C < 600 Bq/m3)


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• The most effective solution is a sub-slab depressurization installed without the reconstruction of floors

• Replacement of existing floors by new ones in which the radon-proof insulation is combined with the soil or air gaps ventilation is selected, when the reconstruction of floors is necessary

• Installation of mechanical ventilation is suitable in houses with low ventilation rate (below 0,3 h-1), or where radon problem is caused by radon from building materials


Measures applied in case of well above the reference level (C > 600 Bq/m3)

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5. SEALING OF RADON ENTRY ROUTES

5.1 Sealing of cracksPassive cracks (without any movement) – polymercement mortars and compounds, epoxy resins, etc.

Active cracks (dilatation movements can occur in the crack) –permanently elastic sealants (acrylic, silicone, bitumen) and PU foams.

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5.2 Sealing of pipe penetrations

Penetrations without dilatation movements

Concrete slab

Subsoil Subsoil

Concrete slab

Gap Groove

Permanently elastic jointing

compound

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5.2 Sealing of pipe penetrations

Penetrations with greater dilatation movements

Concrete slab

Subsoil

Permanently elastic jointing compound

PU foam

Concrete filler

Sealing cord from PE foam

Protective pipe

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5.3 Sealing of covers of inspection chambers

Steel angle

Sealing strip

Silicone/rubber sealing strip

Cover with tiles

Cover from steel plate

Sewage pipe with inspection fitting

Untightbottom

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5.4 Sealing of pipe penetrations through the floor above the cellar/crawl space

Concrete slab

PU foamPlaster

Floor layers

Permanently elastic jointing compound

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5.5 Sealing of doors to the cellar

Wall

Door leaf

Door frame

Silicone/rubber strip sealant

Additional sealant (not necessary)

Rotten and disintegrated door frames and sills and twisted doors must be replaced with new ones.

Doorsteps can reduce air leakage beneath the door.

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5.6 Sealing of the timber staircase

When sealing timber stairs above the cellar be careful about the water vapour condensation

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Additionally applied radon-proof insulation

In existing houses not so effective (less then 45 %), because it usually cannot be applied under the walls and thus radon can be still transported through wall-floor joints. Therefore combination with a soil ventilation system is recommended.

6. AIR-TIGHT SUBSTRUCTURE

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Additionally applied RPI must be connected in an air-tight manner to the existing waterproofing below the walls. Otherwise, radon transport through the wall/floor joints is to be limited by:

6. AIR-TIGHT SUBSTRUCTURE

• installation of sub-slab depressurization with perforated pipes placed in the drainage layer along the perimeter of the existing walls,

• creating a ventilated air gap in the floor construction below or above the radon-proof insulation.

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Options suitable for existing buildings

• Radon sumps

• Perforated tubes drilled beneath existing floors without their damage

• Network of flexible perforated pipes inserted into the drainage layer

• Radon well

7. SUB-SLAB DEPRESSURIZATION

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Selection of an appropriate option depends on:

• ratio of underfloor layer and soil permeabilities kd/ks

• airtightness of floors

• type and geometry of foundations (presence of internal strip foundations)

• preferred method of ventilation (passive or active)

• necessity to reconstruct part or all of the floor area

7. SUB-SLAB DEPRESSURIZATION

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7.1 Radon sump

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Design rules• The floors should be relatively tight• Continuous permeable layer under the slab significantly

increases the effectiveness of the sump• The sump should not be excavated in the soil layer of low

permeability• The min. diameter of the sump is 0,2 m• In existing buildings the forced ventilation is preferred

(underpressure within the sump should be from 100 to 250 Pa)

7.1 Radon sump

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7.1 Radon sump

Examples from UK

By: Chris Scivyer, BRE, UKCTU

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7.1 Radon sump

Examples from Finland

By: Hannu Arvela, STUK, Finland

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7.2 Perforated drilled tubes

Tubes drilled from the external trench

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Example of drilling tubes from the external trench

Indoor radon concentration before

mitigation:

1 145 Bq/m3

Fan NPV 190/125 above the terrain

Drilled pipes ∅ 60 mm, D = 5,0 m

PVC ∅110 mm

PVC ∅110 mm

PVC ∅80 mm

PVC ∅125 mm

WC

LIVING ROOM

BEDROOM

KITCHEN

HALL

BATHROOM

STOREROOM

Single family house

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Example - details of technical solution

Existing floor

Drilled pipe ∅ 60 mm

PU foam

Borehole Ø80 mmPVC pipe Ø60 mm

PVC pipe Ø 80– 125 mm

Backfill

Backfill

PVC pipe Ø80 – 125 mm

PVC pipe Ø125 mm

Wall

Fan at the height min. 600 mm above the terrain

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Example - realization

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Example - radon concentration after the corrective action was applied

During active ventilation radon concentration decreased to the mean value 152 Bq/m3.

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kuchyň

obývací pokoj

ložnice

Kitchen

Living room

Bedroom

Fan in operation

Fan in operation

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Tubes drilled from the cellar

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Indoor radon concentration before

mitigation:

3 240 Bq/m3

LIVING ROOM+

KITCHEN

WC

BATHROOM

HALL

RESTROOM

Single family house

Example of drilling tubes from the cellar

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PVC ∅80 mm

Exhaust PVC pipe ∅ 125 mm inserted in a free flue. Fan installed

above the roof.

PVC ∅100 mm

PVC ∅125 mm

Drilled pipes ∅ 60 mm, D = 5,0 m

CELLAR

Drilled pipe∅ 60 mm, D = 2,5 m

Drilled pipe∅ 60 mm, D = 3,0 m


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Drilled pipe ∅ 60 mm

PU foamBorehole Ø 80 mm

PVC pipe Ø 60 mm

PVC pipe Ø80 – 125 mm

Existing floorBrick vault

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Fan NPV 190/125 at the top of the chimney

Exhaust PVC pipe ∅ 125 mm inserted in a free flue.


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Fan in operationFan in

operation

Living room Bedroom, 2nd floorRestroom Liv. room, 2nd floor

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př. - pokoj s krbem př. - obýv. pokoj + kuchyň patro - obývací pokoj patro - ložnice sever


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Tubes drilled from the internal pit

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Average indoor radon concentration before

mitigation:

1 130 – 1 390 Bq/m3

PVC ∅80 mm

Single family house

PVC ∅ 125 mm.Fan MRF 125

above the chimney.

Perf. PVC ∅60 mm

Perf. PVC ∅ 60 mm

1

HALL

KITCHEN

PANTRY

WC

LIVING ROOM

Drilled pipe∅ 60 mmD=1,0 m



STOVE

PVC ∅125 mm

1

1

BEDROOM

BATHROOM

Example of drilling tubes from the internal pit

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Existing floor

Drilled pipe∅ 60 mm

New floor with a radon-proof insulation jointed in an airtight manner to the walls

Borehole Ø 80 mm

Interconnecting PVC pipe Ø 100 mm

Drilling of perforated pipes


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Fan MRF 125 at the top of the chimney

Exhaust PVC pipe ∅ 125 mm inserted in a free flue.

Fan MRF 125 and a speed regulator


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New floor construction


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komora kuchyň ložnice pokojKitchen Living roomBedroomPantry

Fan in operation – max speed

Fan in operation –

medium speed


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• When drilling the tubes attention must be paid to existing installations (water pipes, cables) under the floor

• At least 1 tube beneath each habitable room• 1 m of the tube has the influence over the floor area:

- to 5 m2…...low tightness of floors ∧ kd/ks ≤ 1- 5–10 m2 ….low tightness of floors ∧ kd/ks > 1 or

floors are relatively tight ∧ kd/ks ≤ 10- 10-15 m2….floors are relatively tight ∧ kd/ks > 10

• Diameter of drilled tubes:- approx. 60 mm for active ventilation- approx. 100 mm for natural ventilation


Design rules

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7.3 Network of flexible perforated pipes

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Example - realization

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• Diameter of pipes:80 – 100 mm for natural ventilation50 – 60 mm for forced ventilation

• Minimum thickness of the drainage layer is 150 mm• Coarse gravel fraction 16/32 mm is used for the drainage

layer• Pipes are laid along walls in order to stop radon from

entering the house through the wall-floor joint or through the vertical holes within the wall

7.3 Network of flexible perforated pipes

Design rules

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Intended mainly for use in sick layers of highly permeable soils (gravel, coarse sand).

Arrangement of a Swedish radon well:1 - 0,4 – 1,0 m diameter pipe

with holes at the bottom end 2 – fan 3 – sealing plastic foil 4 – suction chamber 5 – cover 6 – vent pipe

7.4 Radon well

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Example from Finland

7.4 Radon well

• typical efficiency 70-90%• applicable to single family

houses, row houses and big industrial buildings

• effective up to 30 meters (50m)• fan power 150 W - 300 W• depth 3-5 meters• diameter 0,15 – 0,4 m

By: Hannu Arvela, STUK, Finland

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7.4 Radon well

Examples from Finland

Fan: 250 W, 60 l/s Fan: 260 W, 105l/s

By: Hannu Arvela, STUK, FinlandCTU

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7.5 Fans suitable for SSD systems

• In principle, the fans used for SSD systems in new buildings are also suitable for existing buildings

• Fans must be able to transport soil air with a relative humidity from 80 % to 100 % and to resist the flow of condensed water

• Fan sizing depends on the airtightness of floors, vertical profile of soil permeability and the geometry and length of ventilation pipes

• In-line paddle-wheel fans and roof fans are mostly used

• Fans should not be installed in the habitable zone

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Typical paddle-wheel fan installations

Vent cowl

In-line paddle-

wheel fan

Exhaust pipe inserted into a

free flue

Unused chimney


Exhaust pipe running within the building must be airtight

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In-line paddle-wheel fan

Thermal insulation

Dewatering of condensed water

Ventilating grille

Drip ledge for dewatering of condensed water

Typical paddle-wheel fan installations

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Fans in plumbing and inspection chambers

Fan under the ceiling of the cellar


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Typical roof fan installations


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Typical roof fan installations

Exhaust pipe running in the soil outside the house must be airtight

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8. AIR GAPS DEPRESSURIZATION

• The air gap must be connected in an airtight manner to the surrounding walls.

• Condensation of water vapour in the gap should be prevented.

• Active ventilation creating a slight underpressure within the gap is preferred. Active ventilation is executed without any vent holes delivering external air into the gap.

• Soil air must not be used to ventilate the air gap. When ventilating with internal air, the back flow of air from the gap to the interior must be prevented (e.g. using back-flow valves located in the vent holes).

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An air gap below the radon-proof membrane


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An air gap above the radon-proof membrane


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8. AIR GAPS VENTILATION

Air gap on the external surface of the basement wall

serves as decompression

cavity which eliminates the

pressure difference

between indoors and soil.

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Fans suitable for air gap ventilation

• In principle, the fans used for SSD systems are also suitable for air gap ventilation

• Fan sizing depends on the airtightness of the gap andvolume of air in the gap, i.e. on the area and height of the gap and number and shape of dimples

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Indoor radon concentration before mitigation: 600 Bq/m3

LIVING ROOM

NURSERY

COAL HOME WORKS

CELLAR

KITCHENKITCHEN

BEDROOM

BATHROOM

CORRIDOR

PANTRY

Existing single family house

Example of wrong application of the floor air gap

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Example - original corrective action

1999 - 2000: new floors + passive air gap

ventilation

Indoor radon concentration after corrective action

1 150 – 2 250 Bq/m3

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Example - original corrective action

Reasons for failure:• Natural ventilation through vent holes of

insufficient dimension located in perimeter walls only (without vertical exhaust) – underpressure was not generated in the gap

• Leaky connection of the dimpled membrane to existing walls

• Leaky joints between dimpled membranes

• Underpressure generated in the house sucked radon from the gap to indoor space

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Example - additional corrective action

• Passive ventilation of the floor air gap was changed into an active one by means of connecting existing vent holes on one side of the house to a fan.

• All vent holes on the other side were blocked.

PVC ∅ 125 mm under the terrain

Fan NPV 190/125 above

the terrain

PVC ∅ 80 mm

PVC ∅ 110 mm

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Example - additional corrective action

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During active ventilation indoor radon concentration decreased to the mean value 281 Bq/m3.

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ložnice - 1.NPdětský pokoj - 1.NPkoupelna - 1.NPob.pokoj - 1.NP

Active ventilation

Example - radon concentration after corr. action

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9. HOUSES ON CRAWL SPACES

• Improving the natural ventilation of the crawl space by enlargement of existing vents or adding extra vents

• Converting the natural ventilation into a forced ventilation

• Sealing the floor above the crawl space including services penetrations (in case of timber floors be careful of water vapour condensation)

• Sealing the ground surface

Suitable measures:

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9. HOUSES ON CRAWL SPACES

Example - conversion to forced ventilation

Water and wastewater pipes passing through the crawl space and the floor above the crawl space are to be fitted with thermal insulation

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10. VENTILATION MEASURES

10.1 Improving natural ventilation by installing outdoor air registers and/or adding vertical exhaust pipes

Outdoor air

registers

Vertical exhaust

pipe

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Example of window registers


Interior side

Exterior side

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Example of window registers application

KITCHEN BATHROOM

ROOM FOR CHILDREN

HALL

LIVING ROOM STUDY ROOM

Flat on the 2nd floor of a single family house

Source of indoor radon: lightweight fly ash concrete blocks

Corrective action:

4 window registers installed in window frames

Mean indoor radon concentration before

remediation 745 Bq/m3.

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- liv

ing

room

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- st

udy

room

Air inlets opened Air inlets closed

Living room

Study room

Mean indoor radon concentration after corr. action 94 Bq/m3.

Example - radon concentration after corr. action

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10.2 Increasing air exchange rate by installing mechanical exhaust air ventilation

Exhaust fan

Outdoor air

registers


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10.3 Mechanical supply air ventilation (positive ventilation, house pressurization)


Not suitable for attached houses

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Increased risk of water vapour condensation within

the building envelope construction.

Supply fan + filter + heater

Indoor air escapes through leakages around window

frames and between window frames and casements

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10.4 Mechanical supply and exhaust air ventilation -local ventilation units with heat recovery

Intended for application in particular rooms with the floor area < 45 m2.

Typical characteristics:Power: 4 – 25 WAir flow: 15 – 60 m3/hNoise level: 17 – 49 dB(A)Efficiency of heat recovery: < 75 %


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Effectiveness: 55 – 75 %

Air exchange rate: vent. off 0,1 h-1, vent. on 0,4 h-1

Small ventilation unit with heat recovery installed in the living room

Vent

ilatio

n

Time

Ventilation OFFStove closed

Ventilation ON

Stove closed

Ventilation ONStove opened

Ventilation OFFStove opened

Example of local units application

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10.5 Mechanical supply and exhaust air ventilation forthe whole house

Ventilation unit with filters, heat exchanger, heater and fans.

Due to energy costs the ventilation rate should not exceed 1,0 h-1, otherwise supplementary measures (sealing of the substructure) should be adopted.

All rooms with radon concentration above 400 Bq/m3 should be ventilated.


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11. RADIUM-RICH BUILDING MATERIALS

• Lightweight concrete made of uranium-rich alum shale (Sweden)

• Clinker and clinker concrete products• Brick and concrete products containing slag from iron ore• Products containing coal ash• Materials containing radium-rich phosphate gypsum• Waste materials from uranium mining• Radium-rich granite used as aggregate or building

stones

Materials that may contain larger amounts of radium

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Radium-rich building materials are the source of:• gamma radiation• radon

The level of gamma radiation is directly proportional to the radium content. It is a time independent quantity.

Radon exhalation rate is directly proportional to the radium content, radon emanation coefficient, bulk density and thickness of the material. It is a relatively constant quantity - it does not depend on pressure differences, ventilation rates etc.

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The best way of determining whether the building material contains increased amount of radium is to measure the gamma dose rate from wall and floor structures.

Gamma dose rates 3 times higher than background indicate increased content of radium.

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Examples of radium-rich materials from CZ

• Waste materials from silver and uranium ore processing in Jáchymov

floor fillings, mortars, plasters, stuccoaRa ≈ 1 000 – 100 000 Bq/kg

• Clinker concrete panels (1956 – 60, 1965 – 83)prefabricated single family houses + prefabricated blocks of flatsaRa ≈ 1 000 – 4 000 Bq/kg

• Lightweight fly ash concrete blocks produced before 1984bearing walls for single-family housesaRa ≈ 800 Bq/kg


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11.1 Measures against radon from BM

Suitable measures• Removing building materials• Increasing the ventilation rate• Creating ventilated air gaps around building

constructions

Unsuitable measures• Impermeable surface coatings (low

effectiveness, very sensitive to puncturing and surface condensation)

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• Removing building materials (non-bearing walls, floor fillings, plasters etc.)

• Application of a shielding on the surface of radium-rich building materials (it must be verified that the structure is able to carry the additional load from the shielding)

• Limiting human presence in the proximity of radium-rich building materials

11.2 Measures against gamma radiation from BM

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Effectiveness of shielding materialsAttenuation – ratio between the gamma dose rate with shielding

material to the rate without it

Tabl

e fr

omSa

fety

Gui

de D

S421

11.2 Measures against gamma radiation from BM

Shielding material

Thickness of shielding material (mm) for indicated attenuation

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1

Lead 11 300 kg/m3 0.9 2.3 4.0 6.3 9.3 13 18 26 38

Iron 7 800 kg/m3 6.1 11 17 23 29 37 46 59 81

Barite concrete 3 300 kg/m3 12 24 37 50 65 83 100 130 180

Barite concrete 2 800 kg/m3 18 34 50 66 84 100 130 160 220

Ordinary concrete 2 300 kg/m3 30 50 69 89 110 130 160 200 270

Solid brick 1 800 kg/m3 46 72 100 130 160 190 230 280 370

CTU

IAEA

Testing of shielding effectiveness

Brick lining (sand-lime brick, bulk density 1800 kg/m3, thickness 65 mm) – reduction of the gamma dose rate to 66 % of the initial value.

Brick lining (sand-lime brick, bulk density 1800 kg/m3, thickness 140 mm) – reduction of the gamma dose rate to 54 % of the initial value.

Dry walling – without using a mortar

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Removing plasters and floor fillings

Example of removing radium-rich materials

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Repeated measurement of the gamma dose rate in air


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New plasters and ceilings (soffits)


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12. THERMAL RETROFITTING AND RADON

Energy need of existing buildings is usually reduced by:

• installing ETICS (the external thermal insulation composite system) on the external walls,

• increasing the thickness of the thermal insulation in the roof structures,

• adding thermal insulation in the ceiling below the loft spaces or above the cellars,

• replacing existing windows and entrance doors by new ones with negligibly small infiltration.

CTU

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Energy-saving measures increase the air-tightness of the above-ground building shell. As a consequence,

the house ventilation becomes less intense. Ventilation rates can decrease up to 4 times.

Negative effects:• impaired quality of the indoor environment• increased indoor radon concentration

Thermal retrofitting modifies also the indoor - outdoor pressure difference and thus changes radon supply rate from the soil.

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Replacing windows has the greatest effect on the indoor radon level.

Energy –saving measures are rarely applied to floors and walls in contact with soil. Air-tightness of these structures is usually not improved – radon can still penetrate indoors.

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When installing energy-saving measures the following precautions should be undertaken:• measure indoor radon concentration before and after

thermal retrofitting,

• improve ventilation system,

• increase the air-tightness of floors and walls in contact with soil or adopt another suitable radon countermeasure.Energy consumption cannot be reduced at the

expense of the quality of indoor air.

Build tight – Ventilate right CTU

IAEA

Single family house of the „START“ type built in 1975

Example – consequences of thermal retrofitting

CTU

LVING ROOM

KITCHEN BA

TH

GARAGE

CORRIDOR

HOBBY ROOM

BOILER

UN

DER

GR

OU

ND

FLO

OR

FIR

ST F

LOO

R

IAEA

Prefabricated structure – wall and ceiling panels

WALL PANELS = SOURCE OF RADON AND GAMMA RADIATION

Clinker concreteRadium content:1 000 – 4 000 Bq/kg

Emanation coefficient:0,02

Radon exhalation rate:35 – 150 Bq/m2h

Gamma dose rate:0,5 – 1,5 μSv/h

300

2 50

0


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New air-tight plastic windows

ETICS – 100 mm polystyrene

ROOF – 100 mm polystyrene 2008 – energy-saving measures undertaken


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IAEA

Indoor radon concentration before and after adoption of energy –saving measures (track detectors exposed for 1 year)

Radon concentration [Bq/m3]Roombefore Cbefore after Cafter

Ratio [-] Cbefore/Cafter

Living room + kitchen – 1st

floor 302 753 2,5

Children`s bedroom -2nd floor 296 1 165 3,9Main bedroom - 2nd floor 312 1 524 4,9Kitchen - 2nd floor 438 1 025 2,3Mean values 337 1 117 3,4

Possible reasons•a decrease in the ventilation rate (higher air-tightness)•an increase in the radon exhalation rate (ETICS) – not confirmed


CTU

IAEA

Thermal performance before and after adoption of energy - saving measures – EN ISO 13790:2008

Parameter Before After Ratio Bef/AfIntensity of ventilation n 0,36 h-1 0,106 h-1 3,4Contribution of ventilation to the total energy loss 8,6 % 5,6 % 1,5

Mean thermal transmittance of the building envelope U,em

1,42 W/m2K 0,66 W/m2K 2,2

Specific annual energy need for heating E,A

311 kWh/m2a 110 kWh/m2a 2,8

Total annual energy need for heating EN,H

47,7 MWh 16,9 MWh 2,8

Annual energy savings = 30,8 MWhAnnual costs savings = 1 540 EUR (price of natural gas 50 EUR/MWh)


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Health consequences of energy – saving measures

Additional risk of lung cancer16 x (1117 – 337) / 100 = 125 %

(risk increases by16% per 100 Bq/m3 – Darby S. et.al.)

125 % higher risk of lung

cancer

Savings of at least

1 540 EUR/year


CTU

IAEA

Ensuring the same risk as before energy conversion = increasing the ventilation rate

Forced ventilation with heat recovery

Window registers

5 – 35 m3/h

LVING ROOM

KITCHEN BA

TH

Improved natural ventilation


105428.106,0.1337

1117..1..

=⎟⎠⎞

⎜⎝⎛ −=⎟

⎟⎠

⎞⎜⎜⎝

⎛−=⎟

⎟⎠

⎞⎜⎜⎝

⎛−= Vn

CC

VnC

nCQ after

before

afterafter

before

afterafterm3/h

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Thermal performance after increasing the ventilation rateIntensity of ventilation nafterParameter 0,36 h-1 0,106 h-1

Ratio n0,36/n0,106

[-]Mean thermal transmittance of the building envelope U,em

0,66 W/m2K 0,66 W/m2K 1,0

Specific annual energy need for heating E,A

133 kWh/m2a 110 kWh/m2a 1,2

Total annual energy need for heating

20,4/17,4 MWh 16,9 MWh 1,2/1,03

Natural ventilation Forced ventilation with 85% efficiency of heat recovery

Annual energy savings = 27,3 / 30,3 MWhAnnual costs savings = 1 365 / 1 515 EUR

(price of natural gas 50 EUR/MWh)


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IAEA

Recovery of investments

47,7 MWh/year, 337 Bq/m

3

17,4 MWh/year, 337 Bq/m3

16,9 MWh/year, 1 117 Bq/m320,4 MWh/year, 337 Bq/m3

Comparison of long-term costs


CTUCosts included: installation costs, heating costs, costs for maintenance

and operation of ventilation systems. Annual increase in prices of energy sources is also considered.

IAEA

Not only energy needs, but also indoor air quality should be considered when planning energy conversion of buildings

It is almost always possible to find an optimal solutionOptimal solution = energy needs are kept to a reasonably low level and the indoor radon concentration is kept to an acceptable level (i.e. below the reference level)


CTU

radon remedial measures - kps.fsv.cvut.cz

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