I have a number of windows that were never sealed on the outside (Brick House). Some gaps are larger that others. Should they be sealed with outdoor silicone sealer (-UV) only, or should I attempt to fill the exposed gaps with an expandable foam first, then follow up with sealer after the foam dries? Some gaps are quite deep and would require a lot of silicone... so I am thinking it would be better to use some foam first to get an added benefit of some thermal barrier properties.
As for the expandable foam, I was going to get the yellow stuff in a can, but saw they had one from another manuf specifically for windows which came in white. I know the foam is quite messy, so the white may be less cleanup if it gets out of control in spots. Any thoughts?
Definitely go with the low expansion vs high expansion. The high can cause problems with the frame, and yes, can be more of a mess to clean up when it surges out of the gap. Then as you said, you can finish with a quality silicone.