Replies

1. 
   Piffin | Oct 08, 2011 07:36am | #1

   First be sure the frame is securely fastened and installed and shimmed right all the way around.

   Then use the low expansion foam made specifically for this sort of thing, and doinot fill the cavity first time. Do jst enought get a seal . Then an hour later do another run around the frame.

2. 
   davidmeiland | Oct 08, 2011 10:27am | #2

   You can also

   use "backer rod", which is a long, flexible roll of round foam. I usually get the 3/8" diameter and stuff it into the gap using a stiff putty knife. It is very easy to install and you can keep it flush with the inside of the framing, which is better if you are doing a carefully detailed sill pan.

1. 
   DanH | Oct 08, 2011 10:33am | #3

   You need to be a little careful with backer rod (or stuffed fiberglass, for that matter) since if you use something too wide (or stuff the fiberglass too tightly) then you can cause  the same problem (of bowed sides) that regular foam can cause.

1. 
   davidmeiland | Oct 08, 2011 02:03pm | #4

   After doing hundreds or thousands

   of windows, I would much rather be dealing with one insulated around the edges with backer rod. If there's foam, and the jambs are bowed. I have to cut the foam out completely and re-do it. With backer rod you can pull it right out and replace with smaller if need be. If you use rod that's slightly larger than the gap, there is no problem.

1. 
   DanH | Oct 08, 2011 05:55pm | #5

   Yep, I was just saying that you can overdo it with any technique.