[Greenbuilding] insulating around windows... best practice
RT
archilogic at yahoo.ca
Thu Sep 5 18:52:32 CDT 2013
On Thu, 05 Sep 2013 03:00:39 -0400, Reuben Deumling <9watts at gmail.com>
wrote:
> I like backer rod. My method has evolved into stuffing the appropriate
> diameter backer rod from the outside and from the inside around the
> perimeter of the window.
I tried canned expanding foam once, way back in the 70's or 80's of the
previous millennium when the manufacturers started to boast that their
product didn't use ozone layer-thinning CFCs as a propellant any more.
I didn't like the stoopit stuff because it had a tendency to bridge small
gaps before completely filling the cavity, made friggin' mess, was a PITA
having to trim off the protruding crud, made a friggin' mess and no doubt
a bunch of other irritants that I've long since forgotten about.
However, one good thing came out of the experience.
To address the issue of foam bridging the gap before filling the cavity I
simply made the framing for the rough opening larger than the sizes that
window manufacturers recommended ... say up to 2" larger in width and 1.5"
larger in height than the actual frame size (rounding off the dimension to
a whole number)... but cut the opening in the sheathing very close to the
actual window size.
Then when it came to insulating the shim allowance, it dawned on us that
since the gap was so large and accessible, there was no need to use that
stoopit foam-in-a-can that *everybody* hated.
There was always plenty of EPS scraps around and it was a simple matter to
measure the gap that needed to be filled and rip strips of the EPS scraps
to fit, oversizing the strips so that they needed to be compressed in
order to be shoe-horned into the gap, using 12" drywall knives as the
shoehorns and insertion tools made from scraps or OSB or plywood to
efficiently push the EPS in without damaging the EPS.
But as BCJohn mentioned, insulating the framing gap was only part of the
story. Ensuring continuity of the air barrier by first wrapping a strip of
12" wide black poly around the outside of the window frame (and providing
an extra 8" of length & double folds at each corner to allow for effective
joining to the inside & outside air barrier membranes) was also done.
=== * ===
Rob Tom AOD257
Kanata, Ontario, Canada
< A r c h i L o g i c at Y a h o o dot c a >
(manually winnow the chaff from my edress if you hit "reply")
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