Detailing vapour barrier at windows
Just wondering how other guys detail the vapour barrier at window openings.
Most guys seem to like bringing the housewrap and vapour barrier into the window bay and taping these together.
I have always had a problem with this technique – I think the tape doesn’t adhere well enough, and the spray foam is now adhering to poly and houswrap instead of the wood surround. This doesn’t make for a very secure connection between window and house.
I have always liked to just cut the housewrap and poly flush with the window opening, then foam the cavity well. I think that sealing the window to the wood basically continues the vapour barrier – however I realize that there is some issue where the poly ends at the edge of the opening but it can be caulked here prior to interior wall coverings.
I’d love to hear other folk’s thoughts on this subject which has bothered me for years.
Replies
The link below is a PFD showing the accepted detailing for rainscreen construction in BC which includes window openings. Hope it is of some interest.
http://www.chbavictoria.com/center/members/Rainscreen/ACCEPTED%20RAINSCREEN%20DETAILS-4%20(July%202007).pdf
Thanks for that - they are suggesting lapping the air and vapour barriers like I said - not my favorite way. Interesting that they are still suggesting felt paper over synthetic wrap.
Okay here goes:
Make a tenmporary frame the same size as your jamb extentions (or if your brave enough just use your jambs)
Wrap the temp frame with poly leaving it 3 or 4 inches wider each side
Cut 45º notches in the back corners
Square cut face corners
Drill holes through the frame and screw onto window face
Foam between the poly and trim/head/sill studs
Fold poly over foamed space
Screw flat stock over all until foam cures.
Remove temp frame
Most of the time the foam will glue the VB together, but if not tape and your done.
I have pics if you need them, but they are high-rez ..