Measurement of through-assembly air leakage and its impact on moisture performance of wood-frame walls

Natalia Farkas; Charles R. Boardman; Samuel V. Glass; Samuel L. Zelinka

doi:10.1007/978-981-97-8305-2_37

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Measurement of through-assembly air leakage and its impact on moisture performance of wood-frame walls

Formally Refereed

Authors:

Natalia Farkas, Charles R. Boardman, Samuel V. Glass, Samuel L. Zelinka

Year:

2025

Type:

Paper

Station:

Forest Products Laboratory

DOI:

https://doi.org/10.1007/978-981-97-8305-2_37

Source:

proceedings paper

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Download (PDF 6.75 MB): https://research.fs.usda.gov/download/treesearch/68824.pdf

Abstract

Air leakage is one of the critical moisture sources that may compromise the structural integrity and air quality of wood-frame buildings. The present study investigates air leakage through typical North American oriented strand board (OSB) sheathing using a one-of-a-kind analytical chamber, the CARWASh, which is designed to generate temperature- and humidity-controlled outdoor and indoor conditions for the evaluation of water management performance and moisture dynamics of exterior wall assemblies. We establish a baseline estimate for air leakage through OSB sheathing in full-scale wood-frame walls by combining moisture content, temperature, and relative humidity measurements and a one dimensional transient hygrothermal model. The results show large variations in air leakage between the different OSB panels tested and demonstrate that complete airtightness commonly assumed for wall assemblies in hygrothermal simulations as a computational convenience may not be justifiable. We therefore use the measured data to specify a default air change rate (ACH) value for the average air leakage and assess its impact on the moisture performance of several wood-frame wall assemblies across multiple climate zones. The modeling results imply that a typical through-assembly air leakage likely leads to sizable moisture risk for wood-frame walls under elevated moisture load conditions. This work overall contributes to ongoing efforts in developing a quantitative basis for the evaluation of moisture problems in wood-frame buildings.

Keywords

air leakage, moisture risk, OSB sheathing, hygrothermal model

Citation

Farkas, Natalia; Boardman, Charles R.; Glass, Samuel Z.; Zelinka, Samuel L. 2025. Measurement of through-assembly air leakage and its impact on moisture performance of wood-frame walls. In: Berardi, U., ed. Multiphysics and multiscale building physics. Proc., 9th International Building Physics Conference (IBPC 2024). Vol. 1: Moisture and Materials. Toronto, Ontario, Canada. July 25-27, 2024. Lecture Notes in Civil Engineering. Vol. 552. Singapore: Springer Nature: 270-275. https://doi.org/10.1007/978-981-97-8305-2_37