Volume 6, Issue 4 (April 2009)
Effect of Embedded Seams on Tested Water Vapor Transport Properties of Low Permeance Materials
A method based on ASTM E96/E96M-05 is described for testing the comparative effect of seams and closure types on the water vapor transmission properties of low permeance materials typically applied as moisture vapor retarders. The baseline performance of two materials with water vapor permeance values at 23°C around 5 and 50 ng⋅Pa−1⋅s−1⋅m−2 was measured at both 23°C with 50 % relative humidity and 38°C with 90 % relative humidity. Seams and closures of various types were imposed on both materials including simple overlap, C-fold, lap joint closed with double-sided tape, gap covered by single-sided tape, and lap joint closed with sealant. Testing at 23°C with 50 % relative humidity was repeated using seam widths of 20, 40, and 60 mm. Samples with seam widths of 40 mm were additionally tested at 38°C with 90 % relative humidity. The method gave comparative results indicating that tape and sealant closures are the more effective types in limiting leakage and that seam width can have a significant influence on water vapor transmission through the seam.