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Window insulation advice, please

Mikeljon's picture

Advice from the wise, please. In process of redoing all of the trim in the final room of the whole house renovation. Window casing is removed and there's a puny bit of fiberglass shoved into a few gaps, but most of the space between framing and jamb is open. Typical gap is 1/2" wide. Wall is 2x6 construction. I'm aiming for good air seal. I'm somewhat nervous to use the Great Stuff window and door after a couple of experiences where this stuff bulged out window jambs (even when it says it won't). Room is otherwise refinished, walls renewed/painted, and floor in good shape, and some of the windows are clerestory and 12 feet off the ground--something that is minimal mess potential is also desirable (the great stuff cans, whatever precautions I take, tend to involve spray foam getting everywhere). Thanks for any advice about best systems/products out there.

If you look around you can (post #212670, reply #1 of 12)

If you look around you can probably find a true "low expansion" foam.  I know DAP used to make one variety.  This stuff seems to be water/latex based, and, because it really is low expansion, one can will hardly do a single window.

(Just to reiterate:  Do not use any sort of "urethane foam" for this duty.  The stuff you use should be latex or something similar, and come out of the spray can like thick, bubbly paint, not the fast-expanding smelly glop that is "Great Stuff".)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Great Stuff (post #212670, reply #2 of 12)

Window and door foam will bulge out of the gap. It needs to in order to fill the void and make a complete seal. What it won't do is expand ad distort the jambs or sides of the windows. Mask the opening and cut off the excess. 

Mike, alas I have seen the (post #212670, reply #3 of 12)

Mike, alas I have seen the "Great Stuff" brand of "window and door foam" sold at Home Depot cause jambs to distort.  The stuff appears (or did at the time, maybe 5 years ago) to be just their regular urethane foam "dumbed down" a bit.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Never had a problem. (post #212670, reply #4 of 12)

Never had that problem, but I've always left room for the excess to expand out of the gap.

me too (post #212670, reply #5 of 12)

hence my question here. I was using the disposable cans, though. Any experience with the pro gun (~$50) and the foam that comes in the pro versions? I wondered if that was better. I'm mostly concerned because the windows are 6" deep jambs and thus a lot of room for pressure to build and distort the tacks of the lower sash. I was so concerned about this I was ready to caulk in order to air seal and sacrifice the insulation, assuming that air sealing was the more important of the two. I'm sure someone will tell me if that's a wrong assumption...

I've never used a gun, just (post #212670, reply #6 of 12)

I've never used a gun, just the cans.  The Dap door and window stuff I used is latex (or something similar), and, unlike the urethane stuff, does not expand enormously, nor does it instantly harden but remains soft for days, at least, only forming a thin skin after a few hours.  It's really more like whipped cream.  The urethane stuff expands rapidly and a lot, and it hardens as it expands, so that pressure can easily build up.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Depth of window jamb is not a (post #212670, reply #7 of 12)

Depth of window jamb is not a consideration, because you are not trying to fill the entire thing.  Just run a bead of sealant at the inside wall to provide the air seal.

If you are concerned with adding insulation, slice some Roxul to fit and slide that in before putting the bead of sealant on.

Some reading material:  http://www.finehomebuilding.com/design/d...

Hilti (post #212670, reply #8 of 12)

I'd recommend the Hilti window and door foam CF 812 WD. This is what most professional insulators and window installers around my area use for windows and spot framing gaps. It does not distort jambs and sets up pretty quick (can shave off excess within 15-20 min) They sell a nice starter kit which is comprised of  a case (12 cans) , adjustable gun dispenser, and a can of cleaner for about $275 (if you have an account).

If you're too cheap to spend on that, then you're pretty much stuck wtih G.S. which, BTW, ain't all that great.

thanks (post #212670, reply #9 of 12)

thanks. that's very helpful.

Great Stuff Gun (post #212670, reply #10 of 12)

Got the Great Stuff gun off Amazon. Used the blue cans of window/door insulation. Used one of the black fine tips for application. WOW. Super control. no mess. No insulation flung all over, in my hair, on the walls or floor. I was 12' up on a ladder and had total control. Clean up was easy. No distortion of the jambs, either. Thanks for the advice.

Sealing (post #212670, reply #11 of 12)

Sealing windows and doors is one efficient way of insulation. Sealing is neccesary for windows to ensure energy efficiency and save on budget. It is said that three times sealing means even more savings. These days even Govt. tax credits are available to home and buisness owners.

Would you mind trying 2x4's (post #212670, reply #12 of 12)

Would you mind trying 2x4's for the gap. If you want to fix it right then take the jamb out and add the 2/4's then you can install the door corerctly. Great stuff foam is available at I guess $4. which you can use to fill the gaps. 

As for  aprofessional drywaller, he will bridge the door frame with the drywall and prevent cracks from the edge of the door frame