Now that it's turned cold outside, I've noticed that near my windows is quite drafty. Considering I live in a pretty new raised ranch with modern vinyl insulated windows, I was surprised that it was so noticeable, so I decided to take a look.

After battling the trim for about an hour, I discovered that there is only a minimal amount of fiberglass insulation packed tightly between the window and the rough opening. In some places there is none.

My initial thought is to pull out all the fiberglass and spray some minimally expanding foam into the gap, but since the window isn't centered in the opening, I will just have to use caulk on one side since there isn't a space for the foam.

Since there is housewrap stapled to the rough opening, am I supposed to shoot the foam in between the house wrap and the window frame? What about caulk, should the caulk seal the housewrap to the window frame, or should I be trimming the Tyvek back flush with the window frame, then caulking the window to the rough opening (the wood)? Should I finish up with some foil tape as an added barrier?

The other problem is that the trim work (jam extensions and sill) was assembled as a unit, screwed together, then nailed into the opening on all 4 sides. Even stranger is that the trim "unit" is actually about 2" narrower than the rough opening. As a result, I pretty much had to destroy it to get it out. Since the walls are 2X6, am I just supposed to make jam extensions out of 1" stock to come flush with the wall on the top and sides, nail them into the rough opening and then trim out as desired?

Any help would be really appreciated...