Any red flags for these new window installations?
mapnerd
| Posted in Green Building Techniques on
Hi
I’m having new windows installed at my home in Omaha, NE (zone 5A). I’m an amateur DIY’er, but I’ve never installed windows before so my contractor is doing the installs. Do you see any red flags in this photo? I don’t know what I don’t know so I thought I’d ask one of my most trusted resources – GBA. Thanks for any feedback here and for everything else I learn from this site.
Mike S
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Mike,
The tape at the sill is a problem. The window should have a sill-pan and that should extend out and down under the bottom flange of the window, so any moisture that gets in can drain out there. Right now that moisture will be trapped by the Zip tape over the flange at the sill.
https://www.youtube.com/shorts/h5hUZZ70yig?feature=share
Thank you for your feedback, Malcolm. I will speak with my contractor about it.
If you leave the sill loose so that water can drain as Malcolm suggests, you do need to also address the potential for air leakage at the sill. My go-to is to tape the interior of the window to the framing with Siga Rissan or another slightly vapor permeable tape. This assumes that the window framing is sealed to the ZIP somewhere.
Another approach that I have been using is to tape the full perimeter of the window as you show in your photo, but to use another vapor permeable tape like Siga's Wigluv tape. There should never be a lot of water in the sill pan area, and permeable tape allows this moisture to dry to the outside. Especially with the broad overhangs you have, you have low risk of leakage into the window sill area.