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Re-insulating around windows

11 years ago

Hello Everyone!

I am in the process of insulating around the existing windows in my 1972 split level house in Central PA. There is fiberglass insulation in the gap around the window. I have removed the wood trim from around the windows.

The gap around the windows varies, but it seems that it is filled with fiberglass. Some areas are brown, showing that air movement is a problem.

I am looking to replace the insulation with Great Stuff window foam. From reading around on the forums here, I have found that compressed fiberglass insulation is worthless for insulation. I am under the impression that air sealing is more important then R value in this case.

What all do I have to remove? I have already removed the trim, but there seems to be a second piece of decorate trim that is around the window, which the other trim was attached to. Do I have to remove that to get at the framing around the window for spray-foaming?

Should I remove as much insulation from around the windows as I can? How should I go about cleaning off the surfaces around the window to allow the optimal adhesion from the spray foam to produce as tight a seal as I can?

The gap varies on different sides of the window, and there is a plain wood 'frame' behind the stained trim pieces. how should I get the spray foam in around the wood where the gap is to small between it and the drywall? Should I cut away a bit of the drywall (being sure to leave enough to reattach the trim later) as to fit the nozzle of the Great Stuff spray foam inside, or should I just apply some of the foam directly to the wood and just cut away the excess? Or should I caulk the gaps that are to small, and with what kind of caulk?

Thanks in advance for your help!

Daryl

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Comments (4)

PRO
Windows on Washington Ltd
11 years ago
Don't bother with removing those additional pieces unless they are covering some large void. Even in that case, you can drill a hole and fill (don't overfill) that section.

Shop vac out all the old fiberglass that you can readily get to. The issue is not insulation as much as it is stopping the air (as you noted). That being the case, a small skim layer to seal the envelope would accomplish about 85-90% of the value of the retrofit.

Do yourself a favor and get a foam gun. Don't bother with the straw stuff. It is more cumbersome and less controllable.

Make sure the can is warm and slightly mist the area that you are going to apply the foam to. These low pressure foam are water based cures.

Don't worry about making the substrates super clean. Once you work with the foam, you will quickly realize that it sticks to everything.....trust me.

Do not try to fill the larger void in one pass. You will get over expansion and leave yourself with a mess inside, outside, or both.

Fill the gaps with multiple passes of the foam if they require a larger fill.

Get some disposable tips for the gun and don't remove the can from the gun unless you have another can going on the gun. This will prevent the foam from curing in the gun barrel.

Thankfully these guns will still be available after the Executive orders.

Good luck.
HomeSealed
11 years ago
Perfectly stated.
Only thing I can add is that yes, it is a good idea to cut the drywall back. It will make the foam application much easier and as you mentioned, it will be covered back up by the woodwork.
I'd also reinforce the recommendation to get a foam gun. They sell them at the box stores now for around $50. Just make sure that you clean it well between uses. It comes in handy for other areas around the house as well.
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Thanks Gary. DH said this AM no way are we taking those casings down, though if I want to pull all the FG out of the open ones and spray foam instead I can (he won't). He also corrected me - it was the carpenter who said caulk on the backside of the casings would make a mess, but I can't see how it would be worse than caulking afterward. As far as the casings already up, since our walls aren't really flat (and jambs aren't level with walls - in some cases we've had to cut sheetrock and caulk anyway to get casing to lie flat b/c header is bowed), there are a few spots where there are small gaps at the sides. Carpenter was very neat caulking (white paintable) on tops and sides where he had to cut sheetrock, I can ask him to caulk sides of all the casings (clear this time) and maybe I won't have to paint all around the windows. Our modular was built in 2007 by factory now LEED certified and they still stuffed (not that much) FG around openings. But DH said all the factory-installed windows had house wrap right up to them so shouldn't be any air infiltration so I don't know why DH had to put more FG in. We have 1 site-installed window in MBR that carpenter had to put new jamb in, it was so poorly done so wrap might have been cut way back for that, there was no insulation above the header so we tried to stuff more up there after new jambs were in (carpenter didn't put any in, at least we saw that b4 he put the casing on). Still have all the aprons to do - we can use foam under all the windows. Thanks again!
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dawiest
Original Author
11 years ago
What great advice! Thanks for the speedy replies! I was having troubling finding good howto's for this specific fixup! I'll be sure to come back with a followup as well as ask more around the house fixups on these forums!
PRO
Windows on Washington Ltd
11 years ago
Sounds good!

Keep us posted and pictures with follow up are always fun to see.

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