Window sill (stool) cold, how to seal?

snoopy7548

Diamond Member
Jan 1, 2005
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My house was built in 2012 with (crappy) Simonton double-hung vinyl windows. I'm suspecting that the builder didn't properly insulate the window framing as the window sill (or stool) is extremely cold compared to the temperature inside my house - I measured as low as 42F while the inside temp. was 65F, and the outdoor temp. was 31F. Granted, this was with a Thermopop, but still...

The funny thing is, the area along the top of the window feels perfectly fine; it's just along the jamb and sill, only maybe the first few inches along their plane, that feels cold. The trim isn't cold. I think I know what's going on, though, but I'd like some advice/opinions.

Looking at some really crappy pictures I took when the house was being built, and at my unfinished basement window, there is a 1-1.5" gap between the header and the top of the window frame. In the basement, this was filled with expanding foam, so I'm assuming all of my windows were done the same way, which is why this part feels normal.

The bottom and sides of the window frame butt up against the 2x6 framing of the house, leaving no room to spray in any foam. The build probably sprayed a thin line of foam along this, air sealing it but leaving a void.

Here are some pictures. Any idea if I should start ripping off trim or just deal with it until I replace my windows (something I've been considering, but I have also been thinking about moving in the next year or two). How would I even fill a crack this tight?


Coldest part, right where the vinyl frame meets the sill. The builder didn't caulk this area, but I don't feel or see a draft here when burning an incense stick. 42F
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Gets warmer as you move inwards. 53F.
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Header of unfinished basement window.
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Bottom of unfinished basement window. The builder just sprayed a thin line of foam across this crack, probably about 1/8" wide, but likely smaller on main living area windows. How could I fill something this small?
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Hopefully you can see something here. Crappy phone and dirty lens = terrible pictures. Bedroom 1/2. Notice how the window framing butts right up against the exterior 2x6 framing.
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After drywall. Better camera this time. Seems like I'll have to at least unscrew and cut away the bottom strip of drywall in order to even start, no? I guess the good thing is I can just re-use it, so it doesn't seem too serious or involved. Kitchen.
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Dining room:
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Bathroom:
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Any help is appreciated. Thanks.
 

Greenman

Lifer
Oct 15, 1999
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The bottom of the window didn't get sealed, or there is a gap between the cripple and king stud that wasn't foamed. The only way to know for sure, and to fix it, is to pull the trim and probably some drywall.
 

snoopy7548

Diamond Member
Jan 1, 2005
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Thanks. I'll rip the trim off one window in an unpainted room and see what I can find.

If it turns out that there's no gap between the saddle/sill and finished window sill, what should I do? I really don't want to rip out the finished sill and jambs for all 16 windows. Might as well start getting quotes for replacements (something I've been considering anyways)?
 

Greenman

Lifer
Oct 15, 1999
21,693
6,133
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It's altogether likely that the problem only exists only at the one window, that's the window you need to address, don't bother with the others. Replacing the window probably won't help as most replacement windows fit into the existing window frame. They don't remove exterior siding and trim to remove the window the just stuff a new one in over the old parts.
 

snoopy7548

Diamond Member
Jan 1, 2005
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It's altogether likely that the problem only exists only at the one window, that's the window you need to address, don't bother with the others. Replacing the window probably won't help as most replacement windows fit into the existing window frame. They don't remove exterior siding and trim to remove the window the just stuff a new one in over the old parts.

The thing is, every windowsill in my house feels the same. I only took measurements at that one window.
 

snoopy7548

Diamond Member
Jan 1, 2005
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That makes me think it's a function of how it was all assembled. It could simply be normal conduction at the edge of the window frame.

Yeah, I'm beginning to think that now. If not, the entire void would be cold instead of just the first 2" along the window frame. I'll still rip off the trim of one window and see if there's anything I could do. If not, maybe I'll just buy heavy drapes or those draft-stopper things.

Thanks for your help.
 

mxnerd

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Jul 6, 2007
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Greenman

Lifer
Oct 15, 1999
21,693
6,133
136
Why? What disaster will silicone sealant cause? Seen a lot of videos using silicone to seal windows.

https://www.youtube.com/results?search_query=sealing+windows+with+silicone+
Silicone can't be painted, and most people smear the crap on with their fingers and it ends up a disaster. I saw a house that the owner decided to repaint himself. He slathered that stuff over every seam and crack on the siding, even the horizontal seams between boards. All the paint fell off the silicone within a week. It was a mess that was going to cost him thousands to repair, all because he asked the helpful fellow at the hardware store what the best caulking was, and didn't read the instructions. When you put silicone over grout, moisture gets behind it and mold grows, it's almost impossible to get it all removed. It's a great material in the right place, incorrectly used it's a nightmare.
There is silicone caulk that's paintable, but it's a far different product than straight up silicone seal.