Radon in civil engineering building code, building standards, guidelines for building professionals

Transcription

1 Radon in civil engineering building code, building standards, guidelines for building professionals STUK - Radiation and nuclear safety authority Finland IAEA Regional Workshop, Sofia, Bulgaria Oct 16, 2014

2 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,

3 Building code and guidelines in Finland

4 People: 5.2 mil Housing: 1.4 mil dwellings in houses, 1.1 mil apartments Average radon level: 100 Bq/m 3 Soil: moraine, gravel, sand, clay Climate: Average temperature ( ) South North July +18 o C +15 o C January -4 o C -13 o C Annual +6 o C 0 o C 4

5 Organisations related to indoor radon in dwellings Government STUK Ministry of Social Affairs and Health Local health authorities: health related issues in existing buildings Ministry of Environment Building code Local building authorities: building permission and inspection of new buildings 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 Oct 16,

6 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 Oct 16,

7 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. Oct 16,

8 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/m 3 (annual average) Guideline value for design (maximum acceptable value) Radon included for the first time in 1987 No big effect Oct 16,

9 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 Oct 16,

10 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/m 3, 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) Oct 16,

11 Follow up of new construction Measurements in national radon database Approximately 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 Oct 16,

12 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 Oct 16,

13 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 First guide: Sub-slab suction, 1996 STUK s mitigation guide (136 pp.) In Finnish: STUK-A252, 2012 (2 nd edition) In Swedish: STUK-A237, 2009 Intended for professionals and also for do-it-yourself remediators Oct 16,

14 Radon prevention methods used in Finland

15 Foundation and base floor types and radon Slab on ground Prevalence 2006: 64% High radon levels (mean 96 Bq/m 3 ) Monolithic slab Prevalence 2006: 1% Low radon levels (mean 38 Bq/m 3 ) Crawl-space, suspended floor Prevalence 2006: 19% Low radon levels (mean 44 Bq/m 3 ) Semi-basement and basement Prevalence 2006: 16% High radon (mean 151 Bq/m 3 ) Oct 16,

16 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 in contact with soil Oct 16,

17 Radon resistant new construction, guideline Sealing of joint between slab and foundation wall, and walls in contact with soil Polyestherreinforced bitumen felt cast in direct contact with bitumen felt at least 15 cm Figures from Guide RT Oct 16,

18 Installation of the bitumen felt Figures from Guide RT (Katepal Oy) Oct 16,

19 Example of successful sealing work Bitumen felt before casting of floor slab Oct 16,

20 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/m 3, install a radon fan Oct 16,

21 Installation of radon piping Figure from Guide RT Oct 16,

22 Multi-branch radon piping 1. Suction pipe (perforated drainage pipe) -end of the pipe closed 2. Collector pipe 3. Exhaust duct Figures from Guide RT Oct 16,

23 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 ) 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/m 3, median 58 Bq/m 3 Ref. Arvela H, Holmgren O, Reisbacka H. Radon prevention in new construction in Finland: a nationwide sample survey in Radiation Protection Dosimetry vol. 148, pp , Oct 16,

24 Results, Foundation and radon Lowest concentrations Houses with crawl space, median 29 Bq/m 3 Houses with a monolithic floor slab, median 27 Bq/m 3 Highest concentrations Houses with semi-basement and basement, average 161 Bq/m 3, median 97 Bq/m 3 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/m 3, median 68 Bq/m 3 Oct 16,

25 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 (sample survey 2006) New construction survey (2009) Sample survey (2006) Radon reduction Area (Bq/m 3 ) 237 (Bq/m 3 ) 47% Area2 83 (Bq/m 3 ) 112 (Bq/m 3 ) 26% Whole country 95 (Bq/m 3 ) 142 (Bq/m 3 ) 33% Oct 16,

26 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% Oct 16,

27 Radon concentration grouped by construction year Results of are based on the nationwide sample survey 2006 (STUK-A242, Mäkeläinenet al. 2009). The last bar ( ) represents the results of the new construction study (2009). Decreasing trend Oct 16,

28 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, ReisbackaH. Radon prevention in new construction in Finland: a nationwide sample survey in Radiation Protection Dosimetry vol. 148, pp , Passive radon piping extracts also moisture from the ground below the house Other impurities? Oct 16,

29 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 Oct 16,

30 Remediation methods

31 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 ) Oct 16,

32 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 Radon concentration (Bq/m3) Ventilation and radon Nominal design value in new houses 0 0,5 1 1,5 Air change / hour Oct 16,

33 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 Oct 16,

34 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 Oct 16,

35 Efficiency of radon remediation methods in FIN Sub slab depressurization and radon well most efficient techniques Efficiency typ % 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 (%) Oct 16,

36 RADPAR project

37 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 Oct 16,

38 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-effectivenessand health benefits of radon control strategies Oct 16,

39 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 Oct 16,

40 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/). Oct 16,

41 Radon reduction factors, remediation Method Summary AT BE CZ FI FR NO CH UK Sub-slab depressurization Improving natural ventilation in living spaces Improving mechanical ventilation in living spaces Replacing the existing natural room air ventilation by a mech. exhaust ventilation Installation of a new mech. supply and exhaust ventilation with heat recovery system < Improving ventilation in cellar Decreasing under-pressure in the house Sealing entry routes Improving crawl space ventilation Reduction factor (%), Typ. range Oct 16,

42 Other remediation methods Other methods Country Reduction factor (%), Typ. range Radon well (soil ventilation, outside the house) FIN, CH Soil ventilation through existing drainage piping outside the footings FIN,CH New floors with radon-proof membrane CZE Active floor air gap ventilation CZE Quit using water from drilled well FIN Decreasing under-pressure in the house with insufflating mechanical ventilation FRA 81 Soil ventilation by exhaust air from house NOR Mechanical ventilation of under floor space UK 64 Radon gas barrier POR Building of crawl space POR Oct 16,

43 Typical combinations of remediation methods Combination Country Reduction factor (%), Typ. range Sealing + SSD AUT 80 New floors with radon-proof membrane + sub-slab depressurization New floors with radon-proof membrane + floor air gap depressurization CZE CZE Sealing + building ventilation FRA 72 Sealing + basement ventilation FRA 68 Building and basement ventilation FRA 67 Sealing entry routes + improving natural ventilation NOR Several methods used FIN Sealing + new mech. supply& exhaust ventilation + house pressurization + decreasing under pressure AUT 80 Oct 16,

44 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 and ČSN , Martin Jiránek, Czech Technical University.] Oct 16,

45 Radon reduction factors, prevention Reduction factor (%), Typ. range Prevention method Summary CZ FI NO PT CH UK Passive sub-slab depressurization Active sub-slab depressurization Radon proof insulation, membrane below floor slab Radon proof insulation, membrane above floor slab Sealing the joint of floor slab and foundation wall using membranes Sealing the lead-throughs in structures with soil contact Oct 16,

46 Sealing pipe penetrations Oct 16,

47 Other prevention methods Other methods Double Radon proof insulation membrane, above floor slab combined with depressurization the space between the membranes Country GER Reduction factor (%), Typ. range Arrangement for sub-slab or crawl space ventilation with exhaust air from house Passive ventilation under suspended concrete floor NOR UK 50 Building a crawl space POR Detailed Radon risk maps POR Oct 16,

48 Typical combinations of prevention methods Combination Radon proof membrane above floor slab + active or passive sub-slab ventilation Country CZE Reduction factor (%), Typ. range Radon proof membrane above floor slab + active or passive floor air gap ventilation CZE PassiveSSD+ sealingthejointoffloor slaband foundation wall using bitumen felt FIN Radon proof insulation, membrane below floor slab + passivessd(in highradon areas) IRL Oct 16,

49 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 % passive system: up to 50 % reduction Other methods less efficient, typically < 60 % improving ventilation and sealing RADPAR website: web.jrc.ec.europa.eu/radpar/ Oct 16,

50 RADPAR recommendations and Conclusions

51 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. Oct 16,

52 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 geogenicradon potential (soil permeability and soil air radon concentration) should be taken into account. Oct 16,

53 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 radonprone 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 Oct 16,

54 Examples of foundation and base floor types Figure 1. Typical entry routes in Austria for new houses. Thick concrete plate as a foundation and base floor. Figure 2. Typical entry routes in Finland for slab on ground and separate foundation wall made of light-weight aggregate concrete blocks Oct 16,

55 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. Oct 16,

56 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 Oct 16,

57 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 STUK recommendations: Radon prevention in all new buildings Oct 16,

58 Thank you! Contact information: olli.holmgren(at)stuk.fi p Laippatie 4, P.O.Box 14 FI Helsinki Finland Oct 16,