Replacement Windows – December 1, 2009
air gap at newly replaced window
gap sealed by author
The current practice of replacing single-pane windows with double-glazed off the shelf windows is obviously what is encouraged and required in meeting energy efficiency standards. Reducing heating bills and gaining more comfort and sound transmission is great stuff. That being said, let’s insure that the installation methods actually help the product do what it is suppose to do, reduce air infiltration, sound and moisture. We can best achieve these results by producing a scope of work that includes proper sealing at the exterior side of the building.
Gaps, as shown above, are pre-existing for many reasons. Older building may have severe to moderate sagging at sills, so careful observation and attention to detail, will insure that these gaps are filled with proper back rod material and caulked with the appropriate sealer. Following manufacturer’s instructions is the best way to proceed to gain the most of the material used. Remember, do not assume the contractor will make these repairs.
Window installation contractors do not automatically provide these services, and, if included in the contract scope of work, usually are handled by someone trained in the art of weather sealing. In addition, the 2008 building energy efficiency standards, Section 117, require that openings around windows and doors be caulked, gasketed, weatherstripped or otherwise sealed to limit air leakage. Guess what, the contractor is required to do this.