BCAB #1614 - Window Installation, Sentence 18.104.22.168.(6), Sentences 22.214.171.124.(1) and 126.96.36.199.(1)
November 23, 2005
Re: Window Installation, Sentence 188.8.131.52.(6), Sentences 184.108.40.206.(1) and 220.127.116.11.(1)
The subject is the installation of factory built windows in a wood frame residential building.
Reason for Appeal
The BC Building Code does not specifically describe methods for window installation. Sentence 18.104.22.168.(6) requires penetrations of the air barrier system, such as those created by the installation of windows, shall be sealed to maintain the integrity of the air barrier system over the entire surface. Sentence 22.214.171.124.(1) requires thermally insulated wall assemblies be constructed with a vapour barrier to provide a barrier to diffusion of water vapour from the interior into wall spaces. Sentence 126.96.36.199.(1) requires vapour barriers be installed to protect the entire surfaces of thermally insulated wall assemblies.
The appellant has used the following method for window installation to comply with the Building Code’s air barrier vapour barrier requirements.
- The integrity of the air barrier is met by the window flange being caulked to the wall and on the interior the polyethylene caulked to the window frame and caulking the finished wood liner and trim to the window and drywall.
- The requirement for a continuous vapour barrier is met by the polyethylene being caulked to the window frame.
The appellant considers the additional window installation details requested by the Building Official are not mandatory Code requirements.
Building Official's Position
The Building Official is requesting the window installation include spacer shims below the window unit to allow for drainage, a waterproofing membrane protecting the rough opening sill, and provisions for a sill dam on the interior side. This protection is considered necessary should airborne vapor condense on a non-thermally broken window flange and then accumulate on unprotected wood framing.
Appeal Board Decision #1614
It is the determination of the Board that the additional window installation details requested by the Building Official are not mandatory prescribed requirements of the Code.
The air barrier and vapour barrier design, as proposed, complies with the Code.
George Humphrey, Chair