Radon in civil engineering – building code, building

SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN

RADIATION AND NUCLEAR SAFETY AUTHORITY

Radon in civil engineering – building code,

building standards, guidelines for building

professionals

Olli Holmgren

STUK - Radiation and nuclear safety authority

Finland

IAEA Regional Workshop, Sofia, BulgariaOct 16, 2014



Outline

• Building code and guidelines in Finland

• Radon prevention methods used in Finland

• Short introduction to radon remediation methods

• RADPAR project, results on radon control technologies

• RADPAR recommendations and Conclusions

Oct 16, 2014 2Olli Holmgren



Building code and guidelines in Finland


RADIATION AND NUCLEAR SAFETY AUTHORITY 4

People: 5.2 mil

Housing: 1.4 mil dwellings in houses, 1.1 mil apartments

Average radon level: 100 Bq/m3

Soil: moraine, gravel, sand, clay

Climate:

Average temperature (1981-2010) South North

July +18 oC +15 oC

January -4 oC -13 oC

Annual +6 oC 0 oC



Organisations related to indoor radon in dwellings


Non governmental organizations• Universities: research• Societies in the area of indoor air:

risk communication• Private companies: remediation and

prevention work, measurements

Successful radon policy requires

good cooperation between

governmental and local authorities

as well as expert organizations

Ministry of Social Affairs and Health

Government

Ministry of Environment

Local building authorities: building permission and

inspection of new buildings

Building code

STUK Local health authorities: health related issues in

existing buildings



Reference levels for indoor radon

Decision of the Ministry of Social Affairs and Health 944/1992

• Given based on the radiation law

• Radon concentration in indoor air of a dwelling should not exceed 400 Bq/m3

• A dwelling shall be designed and constructed such that radon concentration would not exceed 200 Bq/m3




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.




Building code, Ventilation 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 appliedOct 16, 2014 9Olli Holmgren



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

• At the end, responsibility of correct solutions regarding the individual house to be constructed belongs to designer (and builder)




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 could be made obligatory as a part of building permission process (but is it legal-technically possible?)

• 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 mitigation guide

• First guide through the activities of Ministry of environment, Ministry of Social Affairs and Health, Helsinki University of Technology and STUK

– Funding of ministries has been important

– First radon mitigation studies in 1985–1986

– First guide: Sub-slab suction, 1996

• STUK’s mitigation guide (136 pp.)

– In Finnish: STUK-A252, 2012 (2nd edition)

– In Swedish: STUK-A237, 2009

• Intended for professionals and also for do-it-yourself remediators




Radon prevention methods used in Finland



Foundation and base floor types and radon


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 construction, guideline

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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Olli Holmgren



Installation of the bitumen felt

18

Figures from Guide RT 38056 (Katepal Oy)

Oct 16, 2014

Olli Holmgren



Example of successful sealing workBitumen felt before casting of floor slab

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Olli Holmgren



Radon resistant new construction, guideline

• 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

20Oct 16, 2014

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

24Olli Holmgren

Oct 16, 2014


RADIATION AND NUCLEAR SAFETY AUTHORITYOlli 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)

25

New construction

survey (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%

Oct 16, 2014


RADIATION AND NUCLEAR SAFETY AUTHORITYOlli 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%

26Oct 16, 2014


RADIATION AND NUCLEAR SAFETY AUTHORITY Olli Holmgren

Oct 16, 2014

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).

27

Decreasing

trend



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

• Other impurities…?




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




Remediation methods



Sub-slab depressurization (SSD)

• Common radon remediation and prevention method

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

– Active SSD: forced ventilation using an exhaust fan

• SSD creates under-pressure under the floor slab and lowers the soil air radon concentration

• In new construction: radon piping can be used(network of flexible perforated pipes )




0

100

200

300

400

500

0 0,5 1 1,5

Ra

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on

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n (

Bq

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Air change / hour

Ventilation and radon

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

• Improving ventilation in cellar or in crawl space also common

Nominal design value

in 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

33Olli Holmgren

Oct 16, 2014



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

• 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




Efficiency of radon remediation methods in FIN

• 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


Radon reduction (%)



RADPAR project



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




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




RAPDAR WP 6 Objectives

• Assessment of potential conflicts between energy conservation in buildings and radon exposure reduction

– Analyses and assessment of current techniques/technologies

• reduction efficiency

• potential impact on energy consumption (qualitative)

– Examination of the potential for conflict or links between radon control technologies and energy conservation in standard, climatic/passive and low energy consumption house technologies

• Establishment of measurement protocols for radon control technologies

• Design of training courses for radon measurement, prevention, remediation, and cost effectiveness analysis




Questionnaire

• National information on remediation and prevention methods

– radon reduction factor

– potential impact on energy consumption (qualitative information)

• Status of radon control in each country

– Action and target levels of radon concentrations

– Number of dwellings exceeding the action level

– Number of dwellings remediated & build with preventive measures

• References to guides, brochures, research reports, website links, other relevant documents

• Sent to all partners in 14 countries

• Ref. RADPAR report: Deliverable 13/1. Assessment of current techniques used for reduction of indoor radon concentration in existing and new houses (2012). Available online at the RADPAR website (web.jrc.ec.europa.eu/radpar/).




Radon reduction factors, remediation

Method Summary AT BE CZ FI FR NO CH UK

Sub-slab depressurization 60-95 80 90 85-95 65-95 89 50-95 90 89

Improving natural ventilation in living spaces

10-50 < 30 15-55 49 10-50 33

Improving mechanical ventilation in living spaces

10-60 5-55 61 10-20

Replacing the existing natural room air ventilation by a mech. exhaust ventilation

10-40 15-45 10-20

Installation of a new mech. supply and exhaust ventilation with heat recovery system

30-60 60 30-60 30-65 10-80

Improving ventilation in cellar 20-60 50 25-50 20-55 47 10-50 75

Decreasing under-pressure in the house

20-70 50 10-50 25 60

Sealing entry routes 10-60 10 10-40 10-55 55 10-60 25 41

Improving crawl space ventilation

40-60 50 40-65 47 10-80 75 47

Reduction factor (%), Typ. range




Other remediation methods

Other methods Country

Reduction factor

(%), Typ. range

Radon well (soil ventilation, outside the house) FIN, CH 80 - 90

Soil ventilation through existing drainage pipingoutside the footings

FIN, CH 50 - 90

New floors with radon-proof membrane CZE 35 - 45

Active floor air gap ventilation CZE 70 - 85

Quit using water from drilled well FIN 25 - 55

Decreasing under-pressure in the housewith insufflating mechanical ventilation

FRA 81

Soil ventilation by exhaust air from house NOR 50 - 95

Mechanical ventilation of under floor space UK 64

Radon gas barrier POR 40 - 70

Building of crawl space POR 60 - 80




Typical combinations of remediation methods

Combination Country

Reduction factor

(%), Typ. range

Sealing + SSD AUT 80

New floors with radon-proof membrane+ sub-slab depressurization

CZE 85 - 95

New floors with radon-proof membrane+ floor air gap depressurization

CZE 80 - 90

Sealing + building ventilation FRA 72

Sealing + basement ventilation FRA 68

Building and basement ventilation FRA 67

Sealing entry routes + improving natural ventilation NOR 20-80

Several methods used FIN 35-75

Sealing + new mech. supply & exhaust ventilation+ house pressurization + decreasing under pressure

AUT 80




Example

• New floors with radon-proof membrane + floor air gap depressurization (Czech Republic)[Ref: RADON REMEDIAL AND PROTECTIVE MEASURES IN THE CZECH REPUBLIC according to the Czech standards ČSN 73 0601 and ČSN 73 0602, Martin Jiránek, Czech Technical University.]


www.ihlcanada.com



Radon reduction factors, prevention

Prevention method Summary CZ FI NO PT CH UK

Passive sub-slab depressurization 20-50 30-40 0-20 20-50 50

Active sub-slab depressurization 70-95 70-90 70-95 40-70 95

Radon proof insulation, membrane below floor slab

30-70 50

Radon proof insulation, membrane above floor slab

30-70 30-70 0-90 30-60 50 50

Sealing the joint of floor slab and foundation wall using membranes

30 0-90 30

Sealing the lead-throughs in structures with soil contact

50 0-90 50

Reduction factor (%), Typ. range




Sealing pipe penetrations

46Olli Holmgren

Oct 16, 2014



Other prevention methods

Other methods Country

Reduction factor

(%), Typ. range

Double Radon proof insulation membrane, abovefloor slab combined with depressurizationthe space between the membranes

GER

Arrangement for sub-slab or crawl spaceventilation with exhaust air from house

NOR 70-95

Passive ventilation under suspendedconcrete floor

UK 50

Building a crawl space POR 70-90

Detailed Radon risk maps POR




Typical combinations of prevention methods

Combination Country

Reduction factor

(%), Typ. range

Radon proof membrane above floor slab+ active or passive sub-slab ventilation

CZE 40-80

Radon proof membrane above floor slab+ active or passive floor air gap ventilation

CZE

Passive SSD + sealing the joint of floor slab andfoundation wall using bitumen felt

FIN 40-60

Radon proof insulation, membrane below floor slab+ passive SSD (In high radon areas)

IRL




Summary, RADPAR

• Effectiveness of different methods is quite similar in all countries

– Unique characteristics must be taken into account

• Active sub-slab depressurization most efficient remediation and prevention method

– reduction of radon concentration by 60 - 95 %

– passive system: up to 50 % reduction

• Other methods less efficient, typically < 60 %

– improving ventilation and sealing

• RADPAR website: web.jrc.ec.europa.eu/radpar/




RADPAR recommendations

and Conclusions



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.

• When necessary, the remediation can be enhanced by improving ventilation of living spaces (including reduction of under-pressure) and sealing entry routes.

• 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.




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.





• 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

54Olli Holmgren

Oct 16, 2014

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




• 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.




Conclusions, remediation in Finland

• 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

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

– Foundation, cellar, base floor

• Active cooperation between ministries, universities and STUK has been important

– Radon mitigation studies have been done actively since 1985=> Results have been utilized in the mitigation guide




Conclusions, prevention in Finland

• New radon regulation in the 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

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

• Radon concentrations have 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




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


Documents

Radon in civil engineering – building code, building