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Tracer gas measurements of water vapour permeability of porous building materials
KTH, Superseded Departments, Building Sciences and Engineering.ORCID iD: 0000-0003-0615-4505
(English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684XArticle in journal (Other academic) Submitted
National Category
Building Technologies
URN: urn:nbn:se:kth:diva-13310OAI: diva2:323525
QS 20120326Available from: 2010-06-11 Created: 2010-06-11 Last updated: 2012-03-26Bibliographically approved
In thesis
1. Alternative methods for analysing moisture transport in buildings: Utilisation of tracer gas and natural stable isotopes
Open this publication in new window or tab >>Alternative methods for analysing moisture transport in buildings: Utilisation of tracer gas and natural stable isotopes
2003 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

New methods, based on tracer gas measurements and isotopicanalysis can be used to evaluate the moisture properties ofbuilding materials and provide the means for forensic analysisof the origins and history of excessive water in buildings, theimmediate practical consequences of which will be the abilityto improve the moisture performance of constructions.

It is shown, in theory and through measurements how thewater vapour permeability of porous building materials can witha good degree of accuracy be estimated with tracer gasmeasurements that provide an efficient alternative to the cupmethod. Complementary measurements may be carried out in orderto evaluate the contribution of surface diffusion and theeventual enhancing effects of moisture content on the diffusioncoefficient. The Random Hopping Model is used to illustrate howthe surface diffusion coefficient depends on the amountadsorbed and the activation energy of migration that can beevaluated from the sorption isotherms.

It is explained how the abundance ratios of two of the mostordinary isotopes of hydrogen and oxygen in water can be usedto determine its history. These isotopes are stable and givethe water a distinct signature that can be used to reveal itssource as shown in a case study. In a contrary manner themeasured isotopic separation can be used to determine therelevance of different transport processes and reactions. It isof central importance that not only does the magnitude ofisotopic separation for the reactions vary for deuterium andoxygen-18 but even the ratio thereof. One of the challenges hasbeen to construct an experimental method for retrieving samplesof water for comparison.

Furthermore this thesis includes an evaluation of a new typeof a light weight construction with loose-fill cellulose fibre,in which the conventional polyethylene vapour barrier has beenreplaced with polypropylene fabric. With a verified model ithas been investigated how the construction would perform fordifferent internal moisture loads and reference climate fromthe literature. The results suggest that this type ofconstruction is not to be recommended.

KEYWORDS:tracer gas, water vapour permeability,diffusion, surface diffusion, isotopic analysis, deuterium,oxygen-18, fractionation, vapour barrier, transient numericalmodelling of diffusion.

Place, publisher, year, edition, pages
Stockholm: KTH, 2003. xii, 57 p.
Trita-BYT, 191
tracer gas, water vapour permeability, diffusion, surface diffusion, isotopic analysis, deuterium, oxygen-18, fractionation, vapour barrier, transient numerical modelling of diffusion
National Category
Building Technologies
urn:nbn:se:kth:diva-3509 (URN)
Public defence
2003-05-09, 00:00
QC 20100611Available from: 2003-04-28 Created: 2003-04-28 Last updated: 2010-06-11Bibliographically approved

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