- Email: [email protected]
Results and conclusions of the Austrian radon mitigation project ‘SARAH’
The Science of the Total Environment 272 Ž2001. 159᎐167
Results and conclusions of the Austrian radon mitigation project ‘SARAH’ F.J. Maringer a,U , M.G. Akis b, H. Kaineder c , P. Kindl d, C. Kralik e, H. Lettner f , S. Lueginger g , E. Nadschlager ¨ c , W. Ringer h , R. Rolle f , f e c , , S. Sperker , H. Stadtmannb, F. Steger b, F. Steinhausler F. Schonhofer ¨ ¨ M. Tschurlovits i , R. Winkler f a Arsenal Research, Faradayg. 3, A-1030 Wien, Austria Austrian Research Center Seibersdorf, LLC-Labor Arsenal, Faradaygasse 3, A-1030 Wien, Austria c Office of the Upper Austrian Go¨ ernment, Stockhofstr. 40, A-4020 Linz, Austria d Technical Uni¨ ersity of Graz, Petersg. 16, A-8010 Graz, Austria e Federal Institute for Food Control and Research, Kinderspitalg. 15, A-1095 Wien, Austria f Uni¨ ersity of Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria g Architectural Office Lueginger, Rainerstr. 14, A-4020 Linz, Austria h Federal Institute for Food Control, Derfflingerstr. 2, A-4017 Linz, Austria i Atominstitute of Austrian Uni¨ ersities, Stadionallee 2, A-1020 Wien, Austria
b
Abstract The Austrian radon mitigation joint research project SARAH Žsupported by the Austrian Ministry of Economy ¨ ., and the Government of Upper Austria., a 2-year follow-up study of the Austrian National Radon Project ŽONRAP was started in 1996. The objectives of the research project were to find simple, cost-effective experimental methods for the characterisation of the radon situation in dwellings and to evaluate technically and economically the implementation of state of the art remedial actions for Austrian house types. After an intercomparison exercise of the assigned radon measuring instruments and detectors five houses were closely examined in regions with elevated radon levels in the federal state of Upper Austria. In this research work for the first time an extended Blower᎐Door method Žwhich is conventionally used for determining the tightness of buildings. was successfully applied to radon diagnosis of buildings. In this paper the methods used for the radon diagnosis, the applied mitigation measures and the related technical and economical aspects are discussed. In conclusion of the results of this project a common strategy for solving the radon problem in Austria in the future is presented briefly. 䊚 2001 Elsevier Science B.V. All rights reserved. Keywords: Radon; Radon mitigation; Radiometric methods; Natural radioactivity; Radiation protection; Construction engineering; Building redevelopment
U
Corresponding author. Tel.: q43-50550-6536; fax: q43-50550-6592. E-mail address: [email protected] ŽF.J. Maringer.. 0048-9697r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 1 . 0 0 6 8 7 - 8
160
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
1. Introduction Since 1992 the Austrian radon survey program ¨ ‘ONRAP’ is continuously carried out to acquire a radon potential map of Austria and to recognise radon prone regions in the country. To minimise the health risk of the population due to indoor radon exposure, well proven and cost-effective concepts and methods are needed for remedial action in high radon-exposure houses and as precautionary measures for new buildings in radon prone areas. This objective has led to a great international experience and to a multitude of mitigated houses in many countries Že.g. EPA, ˚ 1993; Clavensjo 1994; Hamel et ¨ and Akerblom, al., 1996.. In Austria up to now only few houses have been mitigated in regard to radon reduction ŽEnnemoser et al., 1994.. A survey of the indoor air radon situation in the state of Upper Austria ŽFriedmann et al., 1996. resulted in the identifi-
cation of regions with elevated indoor-air radon levels Žannual mean ) 400 Bq my3 .. This research work should increase the experience of Austrian physicists and building engineers in radon diagnosis methods, mitigation and precautionary procedures for Austrian-specific types of houses and building characteristics. The results of this project should become the basis of an Austrian-wide radon mitigation program.
2. Area and applied investigation methods The geological situation in the northern part of Austria ᎏ the granite rocks of the Bohemian massif ᎏ combined with the typical construction of buildings in this region Že.g. hillside position, living space directly positioned on the ground, no cellar below the living space, wooden floor. leads to elevated indoor radon concentrations in many
Fig. 1. Location of the state Upper Austria where the radon mitigated houses are situated.
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
buildings in the northern part of Upper Austria ŽFig. 1.. The first work was to find houses with average radon concentrations higher than 400 Bq my3 . These houses had to be representatives of widespread house types in different regions of Upper Austria. Additionally, the owners and inhabitants had to be convinced of the benefits of a troublesome mitigation procedures. To find houses suitable to these criteria, the owners of 40 houses were contacted by mail and personally. The houses were selected from a list of approximately 1400 dwellings with the highest radon concentrations ¨ of the ‘ONRAP’ study. Only 10 house owners were interested in a remedial action. In consideration of the selection criteia, five buildings in Upper Austria and a radon test house in the Austrian Research Centers Seibersdorf were selected for detailed investigations. Three of them were actually mitigated: a two-family house in Gutau and a farm-house near Konigswiesen ¨ ŽMuhlviertel, Bohemian massif., and a single ¨ family house in Traun Žgravel-terrace .. The twofamily house and the farm-house are in a hillside position without a cellar under the living space. The single-family house has a partial cellar under the living space only. At the practical onset of the project an intercomparison exercise under well-defined on-site conditions was carried out to check the response of different radon measurement instruments and detectors used in this research project. In two intervals ᎏ 3 days and 3 weeks ᎏ a set of passive radon detectors and active instruments was exposed under defined conditions: electret detectors ŽE-PERM., charcoal detectors with LSC- and gamma-evaluation ŽPICORAD, EG & G., track etch detectors ŽMAKROFOL & KfK chamber. and active radon measuring devices ŽALPHA GUARD, ATMOS, PRASSI, ALNOR.. The experiment was performed under realistic temperature and humidity conditions in a closed calibration room of the Geotechnical Institute at the Arsenal, Vienna. The results, uncertainties, and limits of application of the various radon methods are shown and discussed in Maringer et al. Ž1997.. The next step was the experimental investiga-
161
tion of the radon sources and entry paths in each house. The quantities representing the radon situation of a house are primarily the radon concentration ŽBq my3 ., the entry rate ŽBq sy1 ., and the ventilation rate Žl sy1 .. However, these simple quantities cannot be determined exactly at all points of a house all the time. To find acceptable approximations of these quantities a two-stage diagnosis method was chosen. A 2᎐3-week continuous radon monitoring in one room of the house with an ionisation chamber Že.g. Alpha Guard. combined with integrating electret or charcoal detectors in other rooms, was carried out. The evaluation of these measurements was followed by an intensive 1᎐3-day measuring campaign. Additionally, a soil air probe with an air pump and an ionisation chamber ŽAlpha Guard. gave a good indication of the radon potential of the ground. During the measurement periods the meteorological parameters were recorded simultaneously because the meteorological situation strongly effects the indoor radon situation. Together with the active radon measurement instruments a Blower᎐Door was applied ŽFig. 2.. This easily installed tool provides an adjustable pressure reduction in the house of up to y60 Pa. Under reduced-pressure conditions the radon entry paths can be found easily Ž‘sniffing’. with fast responding active radon instruments Že.g. Atmos.. The quantities and time sequence of the air and radon flux through the Blower᎐Door fan gave good estimates of the total average radon entry rate and the ventilation rates at reduced-pressure and normal conditions. The constant reducedpressure condition during the Blower᎐Door operation strongly moderated the current and seasonal meteorological influences. Several complementary measurements were also carried out on the sites Že.g. decay product and thoron measurements, exhalation-rate of building materials, radon and radium analysis of local ground water, radium analysis of local soil samples, assessment of soil permeability..
3. Applied mitigation techniques After the evaluation and discussion of all the
162
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 3. Installation of the perforated suction pipes in the sub-floor aggregate ŽGutau..
Fig. 2. Determination of the radon entry rate with the extended Blower᎐Door method.
measurements made on-site, a cost᎐benefit analysis with regard to the necessary site-specific radon-reduction and possibilities of state-of-theart remedial measures led to a constructional mitigation concept for each building. For the two-family house in Gutau a sub-floor depressuration system was chosen. In two central rooms of the basement perforated suction pipes were installed with sub-floor connections under the adjacent rooms ŽFig. 3.. The three branches of the pipe system were connected to an exhaust fan in the attic ŽFig. 4.. Because of the good soil permeability under the farmhouse near Konigswiesen a sub-house ¨ depressuration concept was selected for this building. Two holes with a diameter of 100 mm and a length of approximately 8 m were drilled at a depth of approximately 1.5᎐2 m under the basement floor of the farmhouse ŽFig. 5.. Then perforated suction pipes with a diameter of 50 mm were installed in the holes and an exhaust fan was connected. The great advantage of this mitigation method is that there is nearly no negative effect on the inhabitants during the installa-
tion. This mitigation method could be applied to many similarly constructed farmhouses in Austria. In the single-family house in Traun a passive sub-floor ventilation system has been installed. For this purpose every 2 m a 50-mm hole was drilled in the base of the living space ŽFig. 6..
Fig. 4. Verification measurement of the radon concentration at the exhaust fan in the attic ŽGutau..
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 5. Drilling of the holes for the installation of the sub.. house suction pipes ŽKonigswiesen ¨
4. Results and discussion The results of all diagnosis and verification measurements and investigations are given in detail in the final report ŽMaringer et al., 1998.. In Table 1 the construction details, the location characteristics and the determined key radon-222 values on the treated sites before mitigation are shown. The highest Rn-222 activity concentration was found on the farm-house site Konigswiesen. ¨ Due to the very high soil permeability Žfluvial gravel. at the building location of Traun on this site the highest Rn-222 transfer from soil into the building indoor-air was found. As an example for the detailed indoor Rn-222 diagnosis investigations, the results of the Rn-222 measurements in
163
Fig. 6. Drilling of the sub-floor ventilation holes in the base of the living space ŽTraun..
the Traun building are given in Table 2. The maximum Rn-222 entry rate was determined during the Blower᎐Door application in the cellar of the building at approximately 5500 Bq my3 hy1 . The entry rate throughout the entire house is approximately 2.7 times higher in the winter season than in the summer season. The average radon reduction after the implementation of the mitigation measures in the three buildings are summarised in Table 3. In the Gutau building the average Rn-222 reduction factor after implementation of the sub-floor suction system is approximately 1r10 during fan operation and approximately 1r2 without fan Žnew construction of the floor in two rooms with sealing between floor and walls, Fig. 7.. The most cost-effective mitigation with specific
Table 1 Construction and local characteristics of the mitigated sites Building
House type
Construction year
Soil type
Average soil air Rn-222 activity conc.
Soil permeability
Average indoor air Rn-222 activity conc.
GUTAU
Two-family house, brick, concrete basement and ceiling, no cellar
1970 q 1992
Weather-worn
78 000 Bq my3
High
500 Bq my3
Farm-house, natural stone and brick, no cellar Single-family house, brick, cellar Žpartly.
17th century q 1989
Weather-worn granite
200 000 Bq my3
High
900 Bq my3
1973
Fluvial gravel
27 000 Bq my3
Very high
600 Bq my3
¨ KONIGSWIESEN TRAUN
granite
164
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Table 2 Radon-222 entry rates in the Traun building before mitigation: seasonal average at natural conditions and during Blower᎐Door application
Blower᎐Door position Room group
Air volume
Average Rn-222 activity conc.
V Žm3 .
cA,⬁ ŽBq my3 .
Blower᎐Door in operation (y50 Pa) Living area 256 Cellar 74 Total house 724
Average air exchange rate
600 900 600
Seasonal a¨ erage (natural condition "0 Pa) Winter Living area 256 1000 Cellar 74 300 Total house 724 600 Summer Living area 256 200 Cellar 74 150 Total house 724 150
Rn-222 mitigation costs of approximately 0.015 EUR my2 per Bq my3 reduction in average indoor Rn-222 was done in Traun ŽTable 4.. The long-term verification of the radon reduction of all the mitigated buildings and the posterior cost᎐effect analysis Žinvestment and operation. and the observation and evaluation of the long-term stability of the remedial measures are scheduled for a period of approximately 10 years. The mitigation measures applied in the three selected buildings were successful. The long-term observation of the indoor Rn-222 at the Traun building will show the necessity of the installation of an active ventilation system for assistance.
Average Rn-222 entry rate Volume-specific
Žhy1 .
qA ŽkBq hy1 .
qA ŽBq sy1 .
qcA ŽBq my3 hy1 .
6.8 6.1 2.9
1040 406 1260
290 113 350
4080 5490 1740
0.5 1.0 0.4
130 22 174
36 6 48
500 300 240
0.7 1.5 0.6
37 17 65
10 5 18
140 230 90
5. Conclusions In the course of this work three main reasons for elevated indoor-air Rn-222 activities in Austrian buildings has been identified: Ž1. weatherworn granitic ground with high permeability due to wash-out of fine grained particles in the soil; Ž2. hillside position of buildings; and Ž3. living space directly over the ground level without a cellar floor below. This project developed an extended Blower᎐Door method and has been improved for the determination of the radon reduction effect after mitigation and for the estimation of the
Table 3 Radon reduction of the mitigated buildings Building
Operation
Average Rn-222 activity conc. after mitigation
Average Rn-222 reduction factor
GUTAU
Passive-without operation of the suction fan Active ᎏ with operation of the suction fan ᎏ 100 Pa low-pressure
250 Bq my3
0.5
50 Bq my3
0.1
360 Pa low-pressure Passive
180 Bq my3 360 Bq my3
0.2 0.6
¨ KONIGSWIESEN TRAUN
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
165
Fig. 7. Results of the Blower᎐Door verification measurement for the determination of the radon reduction in the Gutau building.
average annual mean of the Rn-222 activity concentration of a building. The successful installation of a sub-house depressurisation system in an old farm-house has demonstrated a useful mitigation method without inside remedial activities necessary. One main result of this joint research project is a standard procedure for Rn-222 mitigation of buildings in Austria ŽFig. 8.. The preparation of a more detailed standard procedure for the realisation of mitigation measures in buildings with elevated radon levels Žradon diagnosis, mitigation schedule, verification and acceptance. by a working group of the Austrian standardisation institute is in progress. Based on acquired experience it seems that in the case of new buildings in radon prone areas, in
most cases conventional watertight construction against non-pressurised ground water is solving the radon problem. The experience of the work done and problems arising in this project lead to the following topics for future research work and investigation: 䢇
䢇
The connection between actual health risk and Rn-222 exposition should be investigated in more detail and with less uncertainty for low and medium indoor Rn-222 levels Ž100᎐1000 Bq my3 .. With regard to the quick reaction to the radon problem in Austria and optimisation of the usage of funds, at first only buildings with a Rn-222 activity concentration above 1000 Bq my3 should be treated.
Table 4 Specific radon mitigation costs of the mitigated buildings Building
Living area m2
Average Rn-222 activity conc. before mitigation Bq my3
Average Rn-222 activity conc. after mitigation Bq my3
Total costs of mitigation measures EUR
Specific Rn-222 mitigation costs EUR my2 Bq my3
GUTAU
135
500
50
14000
0.23
¨ KONIGSWIESEN TRAUN
90 110
900 600
180 360
7000 400
0.11 0.015
166
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 8. Flow chart of the run of a Rn-222 mitigation procedure of a building. 䢇
Particular attention should be given to the precaution measures for buildings under construction in radon prone areas. In such occasions suitable reduction effects could be reached with relatively low costs.
For the practical implementation of radon mitigation in Austria in the future, some aspects should be developed such as education of the construction industry, increased information for
the public, installation of public funds for radon mitigation and precaution, registration of radon prone areas in the land utilisation maps, and inclusion of regulations or at least recommendations into the building law.
Acknowledgements The authors are very grateful to the Austrian
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Federal Ministry of Economics for the research grant Žproj. No. F1375r1-IXrAr8r95. and to the Office of the Government of Upper Austria and the participating institutions for their manifold support. References ˚ Clavensjo G. The radon book. Measures against ¨ B, Akerblom radon. Stockholm: Ljunglofs ¨ Offset AB, 1994. 129 pp. Ennemoser O, Ambach W, Oberdorfer E, Brunner P, Schneider P, Keller G. Untersuchungen zur Radonbelastung in probesanierten Hausern der Gemeinde Umhausen.-5. ¨ Zwischenbericht einer Studie im Auftrag des Landesrates fur ¨ Gesundheitswesen des Landes Tirol, Innsbruck, 1994:49 pp. EPA. Radon reduction techniques for existing houses. Techni-
167
cal guidance for active soil depressuration systems. EPAr625rR-93r011. 3rd ed. Washington DC ŽOffice of Research and Development.: EPA, 1993. 298 pp. Hamel P, Lehmann R, Kube G, Couball B, Leissring B. Modellhafte Sanierung radonbelasteter Wohnungen in Schneeberg. Bericht BfS-ST-10r96, Bremerhafen Wirtschaftsverlag NW, 1996:120 pp. Friedmann H, Zimprich P, Atzmuller C et al. The Austrian ¨ radon project. Env Int 1996;22ŽSuppl. 1.:S677᎐S686. Maringer FJ, Akis MG, Kaineder H et al. The Austrian radon intercomparison exercise ‘96. Proc. Protect against Radon at Home and at Work, June 2᎐6, Part II. Praha: Techn. Univ. Prague, 1997:134᎐138. Maringer FJ, Lueginger S, Akis MC et al. Endbericht des Forschungsprojekts F1375 Sanierung radonbelasteter Hauser SARAH ŽFinal report of the Austrian radon miti¨ gation project SARAH.. Bundesministerium fur ¨ wirtschaftl. Wien: Angelegenheiten, Wohnbauforschung, 1998. 114 pp.
Results and conclusions of the Austrian radon mitigation project ‘SARAH’ F.J. Maringer a,U , M.G. Akis b, H. Kaineder c , P. Kindl d, C. Kralik e, H. Lettner f , S. Lueginger g , E. Nadschlager ¨ c , W. Ringer h , R. Rolle f , f e c , , S. Sperker , H. Stadtmannb, F. Steger b, F. Steinhausler F. Schonhofer ¨ ¨ M. Tschurlovits i , R. Winkler f a Arsenal Research, Faradayg. 3, A-1030 Wien, Austria Austrian Research Center Seibersdorf, LLC-Labor Arsenal, Faradaygasse 3, A-1030 Wien, Austria c Office of the Upper Austrian Go¨ ernment, Stockhofstr. 40, A-4020 Linz, Austria d Technical Uni¨ ersity of Graz, Petersg. 16, A-8010 Graz, Austria e Federal Institute for Food Control and Research, Kinderspitalg. 15, A-1095 Wien, Austria f Uni¨ ersity of Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria g Architectural Office Lueginger, Rainerstr. 14, A-4020 Linz, Austria h Federal Institute for Food Control, Derfflingerstr. 2, A-4017 Linz, Austria i Atominstitute of Austrian Uni¨ ersities, Stadionallee 2, A-1020 Wien, Austria
b
Abstract The Austrian radon mitigation joint research project SARAH Žsupported by the Austrian Ministry of Economy ¨ ., and the Government of Upper Austria., a 2-year follow-up study of the Austrian National Radon Project ŽONRAP was started in 1996. The objectives of the research project were to find simple, cost-effective experimental methods for the characterisation of the radon situation in dwellings and to evaluate technically and economically the implementation of state of the art remedial actions for Austrian house types. After an intercomparison exercise of the assigned radon measuring instruments and detectors five houses were closely examined in regions with elevated radon levels in the federal state of Upper Austria. In this research work for the first time an extended Blower᎐Door method Žwhich is conventionally used for determining the tightness of buildings. was successfully applied to radon diagnosis of buildings. In this paper the methods used for the radon diagnosis, the applied mitigation measures and the related technical and economical aspects are discussed. In conclusion of the results of this project a common strategy for solving the radon problem in Austria in the future is presented briefly. 䊚 2001 Elsevier Science B.V. All rights reserved. Keywords: Radon; Radon mitigation; Radiometric methods; Natural radioactivity; Radiation protection; Construction engineering; Building redevelopment
U
Corresponding author. Tel.: q43-50550-6536; fax: q43-50550-6592. E-mail address: [email protected] ŽF.J. Maringer.. 0048-9697r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 1 . 0 0 6 8 7 - 8
160
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
1. Introduction Since 1992 the Austrian radon survey program ¨ ‘ONRAP’ is continuously carried out to acquire a radon potential map of Austria and to recognise radon prone regions in the country. To minimise the health risk of the population due to indoor radon exposure, well proven and cost-effective concepts and methods are needed for remedial action in high radon-exposure houses and as precautionary measures for new buildings in radon prone areas. This objective has led to a great international experience and to a multitude of mitigated houses in many countries Že.g. EPA, ˚ 1993; Clavensjo 1994; Hamel et ¨ and Akerblom, al., 1996.. In Austria up to now only few houses have been mitigated in regard to radon reduction ŽEnnemoser et al., 1994.. A survey of the indoor air radon situation in the state of Upper Austria ŽFriedmann et al., 1996. resulted in the identifi-
cation of regions with elevated indoor-air radon levels Žannual mean ) 400 Bq my3 .. This research work should increase the experience of Austrian physicists and building engineers in radon diagnosis methods, mitigation and precautionary procedures for Austrian-specific types of houses and building characteristics. The results of this project should become the basis of an Austrian-wide radon mitigation program.
2. Area and applied investigation methods The geological situation in the northern part of Austria ᎏ the granite rocks of the Bohemian massif ᎏ combined with the typical construction of buildings in this region Že.g. hillside position, living space directly positioned on the ground, no cellar below the living space, wooden floor. leads to elevated indoor radon concentrations in many
Fig. 1. Location of the state Upper Austria where the radon mitigated houses are situated.
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
buildings in the northern part of Upper Austria ŽFig. 1.. The first work was to find houses with average radon concentrations higher than 400 Bq my3 . These houses had to be representatives of widespread house types in different regions of Upper Austria. Additionally, the owners and inhabitants had to be convinced of the benefits of a troublesome mitigation procedures. To find houses suitable to these criteria, the owners of 40 houses were contacted by mail and personally. The houses were selected from a list of approximately 1400 dwellings with the highest radon concentrations ¨ of the ‘ONRAP’ study. Only 10 house owners were interested in a remedial action. In consideration of the selection criteia, five buildings in Upper Austria and a radon test house in the Austrian Research Centers Seibersdorf were selected for detailed investigations. Three of them were actually mitigated: a two-family house in Gutau and a farm-house near Konigswiesen ¨ ŽMuhlviertel, Bohemian massif., and a single ¨ family house in Traun Žgravel-terrace .. The twofamily house and the farm-house are in a hillside position without a cellar under the living space. The single-family house has a partial cellar under the living space only. At the practical onset of the project an intercomparison exercise under well-defined on-site conditions was carried out to check the response of different radon measurement instruments and detectors used in this research project. In two intervals ᎏ 3 days and 3 weeks ᎏ a set of passive radon detectors and active instruments was exposed under defined conditions: electret detectors ŽE-PERM., charcoal detectors with LSC- and gamma-evaluation ŽPICORAD, EG & G., track etch detectors ŽMAKROFOL & KfK chamber. and active radon measuring devices ŽALPHA GUARD, ATMOS, PRASSI, ALNOR.. The experiment was performed under realistic temperature and humidity conditions in a closed calibration room of the Geotechnical Institute at the Arsenal, Vienna. The results, uncertainties, and limits of application of the various radon methods are shown and discussed in Maringer et al. Ž1997.. The next step was the experimental investiga-
161
tion of the radon sources and entry paths in each house. The quantities representing the radon situation of a house are primarily the radon concentration ŽBq my3 ., the entry rate ŽBq sy1 ., and the ventilation rate Žl sy1 .. However, these simple quantities cannot be determined exactly at all points of a house all the time. To find acceptable approximations of these quantities a two-stage diagnosis method was chosen. A 2᎐3-week continuous radon monitoring in one room of the house with an ionisation chamber Že.g. Alpha Guard. combined with integrating electret or charcoal detectors in other rooms, was carried out. The evaluation of these measurements was followed by an intensive 1᎐3-day measuring campaign. Additionally, a soil air probe with an air pump and an ionisation chamber ŽAlpha Guard. gave a good indication of the radon potential of the ground. During the measurement periods the meteorological parameters were recorded simultaneously because the meteorological situation strongly effects the indoor radon situation. Together with the active radon measurement instruments a Blower᎐Door was applied ŽFig. 2.. This easily installed tool provides an adjustable pressure reduction in the house of up to y60 Pa. Under reduced-pressure conditions the radon entry paths can be found easily Ž‘sniffing’. with fast responding active radon instruments Že.g. Atmos.. The quantities and time sequence of the air and radon flux through the Blower᎐Door fan gave good estimates of the total average radon entry rate and the ventilation rates at reduced-pressure and normal conditions. The constant reducedpressure condition during the Blower᎐Door operation strongly moderated the current and seasonal meteorological influences. Several complementary measurements were also carried out on the sites Že.g. decay product and thoron measurements, exhalation-rate of building materials, radon and radium analysis of local ground water, radium analysis of local soil samples, assessment of soil permeability..
3. Applied mitigation techniques After the evaluation and discussion of all the
162
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 3. Installation of the perforated suction pipes in the sub-floor aggregate ŽGutau..
Fig. 2. Determination of the radon entry rate with the extended Blower᎐Door method.
measurements made on-site, a cost᎐benefit analysis with regard to the necessary site-specific radon-reduction and possibilities of state-of-theart remedial measures led to a constructional mitigation concept for each building. For the two-family house in Gutau a sub-floor depressuration system was chosen. In two central rooms of the basement perforated suction pipes were installed with sub-floor connections under the adjacent rooms ŽFig. 3.. The three branches of the pipe system were connected to an exhaust fan in the attic ŽFig. 4.. Because of the good soil permeability under the farmhouse near Konigswiesen a sub-house ¨ depressuration concept was selected for this building. Two holes with a diameter of 100 mm and a length of approximately 8 m were drilled at a depth of approximately 1.5᎐2 m under the basement floor of the farmhouse ŽFig. 5.. Then perforated suction pipes with a diameter of 50 mm were installed in the holes and an exhaust fan was connected. The great advantage of this mitigation method is that there is nearly no negative effect on the inhabitants during the installa-
tion. This mitigation method could be applied to many similarly constructed farmhouses in Austria. In the single-family house in Traun a passive sub-floor ventilation system has been installed. For this purpose every 2 m a 50-mm hole was drilled in the base of the living space ŽFig. 6..
Fig. 4. Verification measurement of the radon concentration at the exhaust fan in the attic ŽGutau..
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 5. Drilling of the holes for the installation of the sub.. house suction pipes ŽKonigswiesen ¨
4. Results and discussion The results of all diagnosis and verification measurements and investigations are given in detail in the final report ŽMaringer et al., 1998.. In Table 1 the construction details, the location characteristics and the determined key radon-222 values on the treated sites before mitigation are shown. The highest Rn-222 activity concentration was found on the farm-house site Konigswiesen. ¨ Due to the very high soil permeability Žfluvial gravel. at the building location of Traun on this site the highest Rn-222 transfer from soil into the building indoor-air was found. As an example for the detailed indoor Rn-222 diagnosis investigations, the results of the Rn-222 measurements in
163
Fig. 6. Drilling of the sub-floor ventilation holes in the base of the living space ŽTraun..
the Traun building are given in Table 2. The maximum Rn-222 entry rate was determined during the Blower᎐Door application in the cellar of the building at approximately 5500 Bq my3 hy1 . The entry rate throughout the entire house is approximately 2.7 times higher in the winter season than in the summer season. The average radon reduction after the implementation of the mitigation measures in the three buildings are summarised in Table 3. In the Gutau building the average Rn-222 reduction factor after implementation of the sub-floor suction system is approximately 1r10 during fan operation and approximately 1r2 without fan Žnew construction of the floor in two rooms with sealing between floor and walls, Fig. 7.. The most cost-effective mitigation with specific
Table 1 Construction and local characteristics of the mitigated sites Building
House type
Construction year
Soil type
Average soil air Rn-222 activity conc.
Soil permeability
Average indoor air Rn-222 activity conc.
GUTAU
Two-family house, brick, concrete basement and ceiling, no cellar
1970 q 1992
Weather-worn
78 000 Bq my3
High
500 Bq my3
Farm-house, natural stone and brick, no cellar Single-family house, brick, cellar Žpartly.
17th century q 1989
Weather-worn granite
200 000 Bq my3
High
900 Bq my3
1973
Fluvial gravel
27 000 Bq my3
Very high
600 Bq my3
¨ KONIGSWIESEN TRAUN
granite
164
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Table 2 Radon-222 entry rates in the Traun building before mitigation: seasonal average at natural conditions and during Blower᎐Door application
Blower᎐Door position Room group
Air volume
Average Rn-222 activity conc.
V Žm3 .
cA,⬁ ŽBq my3 .
Blower᎐Door in operation (y50 Pa) Living area 256 Cellar 74 Total house 724
Average air exchange rate
600 900 600
Seasonal a¨ erage (natural condition "0 Pa) Winter Living area 256 1000 Cellar 74 300 Total house 724 600 Summer Living area 256 200 Cellar 74 150 Total house 724 150
Rn-222 mitigation costs of approximately 0.015 EUR my2 per Bq my3 reduction in average indoor Rn-222 was done in Traun ŽTable 4.. The long-term verification of the radon reduction of all the mitigated buildings and the posterior cost᎐effect analysis Žinvestment and operation. and the observation and evaluation of the long-term stability of the remedial measures are scheduled for a period of approximately 10 years. The mitigation measures applied in the three selected buildings were successful. The long-term observation of the indoor Rn-222 at the Traun building will show the necessity of the installation of an active ventilation system for assistance.
Average Rn-222 entry rate Volume-specific
Žhy1 .
qA ŽkBq hy1 .
qA ŽBq sy1 .
qcA ŽBq my3 hy1 .
6.8 6.1 2.9
1040 406 1260
290 113 350
4080 5490 1740
0.5 1.0 0.4
130 22 174
36 6 48
500 300 240
0.7 1.5 0.6
37 17 65
10 5 18
140 230 90
5. Conclusions In the course of this work three main reasons for elevated indoor-air Rn-222 activities in Austrian buildings has been identified: Ž1. weatherworn granitic ground with high permeability due to wash-out of fine grained particles in the soil; Ž2. hillside position of buildings; and Ž3. living space directly over the ground level without a cellar floor below. This project developed an extended Blower᎐Door method and has been improved for the determination of the radon reduction effect after mitigation and for the estimation of the
Table 3 Radon reduction of the mitigated buildings Building
Operation
Average Rn-222 activity conc. after mitigation
Average Rn-222 reduction factor
GUTAU
Passive-without operation of the suction fan Active ᎏ with operation of the suction fan ᎏ 100 Pa low-pressure
250 Bq my3
0.5
50 Bq my3
0.1
360 Pa low-pressure Passive
180 Bq my3 360 Bq my3
0.2 0.6
¨ KONIGSWIESEN TRAUN
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
165
Fig. 7. Results of the Blower᎐Door verification measurement for the determination of the radon reduction in the Gutau building.
average annual mean of the Rn-222 activity concentration of a building. The successful installation of a sub-house depressurisation system in an old farm-house has demonstrated a useful mitigation method without inside remedial activities necessary. One main result of this joint research project is a standard procedure for Rn-222 mitigation of buildings in Austria ŽFig. 8.. The preparation of a more detailed standard procedure for the realisation of mitigation measures in buildings with elevated radon levels Žradon diagnosis, mitigation schedule, verification and acceptance. by a working group of the Austrian standardisation institute is in progress. Based on acquired experience it seems that in the case of new buildings in radon prone areas, in
most cases conventional watertight construction against non-pressurised ground water is solving the radon problem. The experience of the work done and problems arising in this project lead to the following topics for future research work and investigation: 䢇
䢇
The connection between actual health risk and Rn-222 exposition should be investigated in more detail and with less uncertainty for low and medium indoor Rn-222 levels Ž100᎐1000 Bq my3 .. With regard to the quick reaction to the radon problem in Austria and optimisation of the usage of funds, at first only buildings with a Rn-222 activity concentration above 1000 Bq my3 should be treated.
Table 4 Specific radon mitigation costs of the mitigated buildings Building
Living area m2
Average Rn-222 activity conc. before mitigation Bq my3
Average Rn-222 activity conc. after mitigation Bq my3
Total costs of mitigation measures EUR
Specific Rn-222 mitigation costs EUR my2 Bq my3
GUTAU
135
500
50
14000
0.23
¨ KONIGSWIESEN TRAUN
90 110
900 600
180 360
7000 400
0.11 0.015
166
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Fig. 8. Flow chart of the run of a Rn-222 mitigation procedure of a building. 䢇
Particular attention should be given to the precaution measures for buildings under construction in radon prone areas. In such occasions suitable reduction effects could be reached with relatively low costs.
For the practical implementation of radon mitigation in Austria in the future, some aspects should be developed such as education of the construction industry, increased information for
the public, installation of public funds for radon mitigation and precaution, registration of radon prone areas in the land utilisation maps, and inclusion of regulations or at least recommendations into the building law.
Acknowledgements The authors are very grateful to the Austrian
F.J. Maringer et al. r The Science of the Total En¨ ironment 272 (2001) 159᎐167
Federal Ministry of Economics for the research grant Žproj. No. F1375r1-IXrAr8r95. and to the Office of the Government of Upper Austria and the participating institutions for their manifold support. References ˚ Clavensjo G. The radon book. Measures against ¨ B, Akerblom radon. Stockholm: Ljunglofs ¨ Offset AB, 1994. 129 pp. Ennemoser O, Ambach W, Oberdorfer E, Brunner P, Schneider P, Keller G. Untersuchungen zur Radonbelastung in probesanierten Hausern der Gemeinde Umhausen.-5. ¨ Zwischenbericht einer Studie im Auftrag des Landesrates fur ¨ Gesundheitswesen des Landes Tirol, Innsbruck, 1994:49 pp. EPA. Radon reduction techniques for existing houses. Techni-
167
cal guidance for active soil depressuration systems. EPAr625rR-93r011. 3rd ed. Washington DC ŽOffice of Research and Development.: EPA, 1993. 298 pp. Hamel P, Lehmann R, Kube G, Couball B, Leissring B. Modellhafte Sanierung radonbelasteter Wohnungen in Schneeberg. Bericht BfS-ST-10r96, Bremerhafen Wirtschaftsverlag NW, 1996:120 pp. Friedmann H, Zimprich P, Atzmuller C et al. The Austrian ¨ radon project. Env Int 1996;22ŽSuppl. 1.:S677᎐S686. Maringer FJ, Akis MG, Kaineder H et al. The Austrian radon intercomparison exercise ‘96. Proc. Protect against Radon at Home and at Work, June 2᎐6, Part II. Praha: Techn. Univ. Prague, 1997:134᎐138. Maringer FJ, Lueginger S, Akis MC et al. Endbericht des Forschungsprojekts F1375 Sanierung radonbelasteter Hauser SARAH ŽFinal report of the Austrian radon miti¨ gation project SARAH.. Bundesministerium fur ¨ wirtschaftl. Wien: Angelegenheiten, Wohnbauforschung, 1998. 114 pp.