Large-Scale Experimental Investigation of Wood-Frame Walls Exposed to Simulated Rain Penetration in a Cold Climate

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As rain can be the most important potential source of moisture in wall assemblies, an experimental investigation compares the wetting and drying patterns of 15 walls subjected to simulated rain penetration in the stud cavity.

A 2-story test hut was built within a large Environmental Chamber to receive 31 wall specimens of 2’-4” x 8’ (0.9 m x 2.4 m). The 15 specimens discussed in this paper consider three different types of sheathing – oriented strand board (OSB), plywood and fiberboard, two exterior claddings – wood cladding on furring and cement stucco on metallic lath (no air space), and two different interior finish permeances – paint with/without polyethylene sheet. The walls were built with 2” x 6” (38 mm x 140 mm) studs and insulated with glass fiber insulation. The moisture content of the bottom plate and sheathing in each wall was monitored using moisture content probes and gravimetric measurements. The exterior conditions were controlled to reproduce August through November weather conditions for Montreal. The interior conditions were maintained at 21ºC and 40% RH. To simulate rain penetration conditions, the wall specimens received a wetted insert, i.e. a wetted bottom plate, at the beginning of each climatic period.

Gravimetry results obtained for the different wall specimens are presented and discussed. The moisture content distribution and levels in the bottom plates and sheathing through the four climatic sets of conditions show an increase in spread as conditions are cooler. The potential influence of the sheathing material, of the cladding with and without air space, and of the level of permeance of the interior finish is discussed. Overall, the walls with stucco cladding retained greater moisture content than those with a furred wood cladding.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: Dual

Citation: Thermal Performance of Exterior Envelopes of Whole Buildings X

Product Details

Published:

2008

Number of Pages:

9

File Size:

1 file , 3.9 MB

Product Code(s):

D-BldgsX163