Wooden roof structures with high vapor retarder, low vapor retarder, and moisture-dependent vapor retarder

Research output: Contribution to journalConference articleContributedpeer-review

Contributors

  • Heiko Fechner - , Chair of Building Physics, TUD Dresden University of Technology (Author)
  • Peter Häupl - , TUD Dresden University of Technology (Author)

Abstract

In the moderately cold climate areas, the assessment of the vapor retarder for insulated wooden roof structures is important. In the case of a tight roofing felt, it is common to use retarders with a resistance of 100 m at the inside of the structures. A condensation amount of less than 50 g/m2 will arise. However, in the case of built-in moisture, the structure cannot dry out and damage will follow. With a resistance of 2 m, the amount of condensation increases to 250 g/m2, but the built-in-moisture can dry out. For a pitched roof (toward the south) with an extremely high initial wooden moisture content of 30 V-% (0.3 m3/m3) the drying process takes about four years. With a moisture-dependent vapor retarder (wintertime 4 m, summertime 0.5 m) the moisture behavior of the insulated wooden structure can be improved further. In the case of a vapor permeable roofing membrane, the drying out process of the rafters and the roof battens can be reduced to three months without any condensation in the future. A simulation has been performed for coupled heat, air, and moisture transfer in building structures with hourly values of the Test Reference Year of Munich as boundary conditions.

Details

Original languageEnglish
JournalThermal Performance of Exterior Envelopes of Buildings - International Conference
Publication statusPublished - 1 Jan 2001
Peer-reviewedYes

Conference

Title8th International Conference on Thermal Performance of Exterior Envelopes of Whole Buildings 2001
Duration2 - 7 December 2001
CityClearwater
CountryUnited States of America

External IDs

ORCID /0000-0003-0771-6370/work/142251602

Keywords

ASJC Scopus subject areas