I have vinyl windows with wood frames like this-
(https://i821.photobucket.com/albums/zz132/dug62/_DSC0017-1.jpg)
Does the wood frame on the interior get nailed at all? I didn't think so but I noticed they are pretty flexible and I am concerned that even low expansion foam insulation might bow them if I don't. ???
dug,
I would tear off glass from batts and stuff it, that way you can control the bow.
I do know the interior does not get nailed.