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The air leakage characteristics of eight methods of sealing, or otherwise treating, the rough openings (R/O) found around window and door frames were evaluated under laboratory conditions. The eight methods studied were: 1. no treatment (empty), 2. conventional (fiber glass), 3. densely packed, fiber glass, 4. backer rod, 5. casing tape, 6. poly-return, 7. poly-wrap, and 8. foamed-in-place urethane.
The untreated R/O (Method 1) displayed the greatest leakage while the second largest occurred using the conventional practice of packing fiber glass into the R/O space (Method 2). In contrast, Methods 5, 6, 7 and 8 were able to reduce R/O leakage to negligible levels.
To relate these results to the overall building leakage, an estimate was made of the percentage of the total building leakage which would occur through the R/Os in a typical 97 m2 (1040 ft2) bungalow. Two levels of total house airtightness were assumed: 1.5 air changes per hour at 50 Pa (ac/h50) representing tight construction and 5.0 ac/h50 (representing loose construction). For the tight house with Method 1 (no treatment), the R/O leakage accounted for 39% of the total house leakage; with Method 2 (conventional), this figure dropped to 14%. With each of Methods 5 to 8, the contribution of R/O leakage to total house leakage was less than 1%. For the loose house and Method 1, the R/O leakage was 12% of the total; with Method 2, it dropped to 4% and with Methods 4 to 8, it was less than 1%.
The incremental builder cost of each technique (i.e., exclusive of mark-up for overhead, profit, etc.) was estimated assuming Method 2 as conventional practice with a base cost of zero. Incremental costs ranged from a low of $18 per house for the urethane approach (Method 8) to $84 per house for the poly-wrap technique (Method 7).
residential airtightness, air leakage, rough-opening air leakage, window, door air leakage
Proskiw Engineering Ltd., Winnipeg, Manitoba