Window Dressing

After a few hiccups with our supplier, we finally have all the windows installed.  It’s amazing how much of a difference that makes to the environment inside the house. I love fresh air, but when it’s blowing the plan-set all over the living room, there can be too much of a good thing.

installed - awaiting detailing

installed – awaiting detailing

The installation process went well. Removing an operator here and there helped lighten the load a bit;  tri-pane windows are noticeably more heavy than their double-pane counterparts.  Installation started out the same as any other house… a level, some cedar shims, fasteners and special low-expansion foam (which remains flexible – this is important!).  The first photo shows an installed window in the SIP wall assembly.  What you can’t see (translation: what I forgot to take a picture of) is that each window opening was first detailed with a trowel-on elastomeric water-proof membrane, also called the “Weather-Resistive Barrier” or WRB.  The most common WRB’s are of the “house-wrap” variety, of which Typar and Tyvek are the most popular. The main detriment to wrapping a WRB around a window/door opening is that it makes it difficult to air-seal on both sides of the membrane.  With a trowel-on membrane, it is sealed to the substrate (frame opening) when applied and the window is subsequently sealed to it; far less opportunity for air leakage.  The other detail missing is the outermost 2×4 window buck hiding just behind the inside edge of the window frame. 2013-11-15 11.11.40

Though not significant, that 2×4 does represent a thermal bridge in the window installation so we chose to isolate it by wrapping the interior of each window opening with polyiso insulation.  Two beads of spray-foam and a bead of calking ensure it also becomes part of the vapour-barrier continuation.

Air-sealing tape applied

Air-sealing tape applied

Finally, an application of air-sealing tape between the window frame and the foil-faced polyiso completes the air-tight seal.

These pictures also give you a glimpse of the 2×4 service partition. That partition is currently being well-utilized by the electrical, plumbing and HVAC subcontractors, and we’re happy to see that, knowing the alternative would be to carve holes and channels into the OSB vapour-barrier.  We have chamfered the sides and top of the service partition around window openings as an architectural detail; this also improves the field of view and the amount of light allowed to enter the rooms.

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3 thoughts on “Window Dressing

  1. I bet the windows have improved the working enviro. I feel for our crew as they will have a long cold haul until we reach window install stage. I look forward to seeing more of Kingston Passive House. You may be getting a call or two for some tips as we fumble through our progression.
    Best,
    Marilynn (aka Mimi)

  2. Hi great information, thanks for sharing your project. What windows did you select for your project? We are designing a PH in Halifax and interested in all Canadian experiences. Thanks

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