Knee wall space
Hello,
I’m not a builder or expert.
I had my (2) knee wall space foamed with open cell foam at the slope of my roof as well as the outside walls.The inner walls to the rooms were not foamed.
I put down some carpet in the knee wall area so I can use the space for storage.(I cut in some hatch panels.)
My 2 dormers inside walls (on the roomside)in the rooms get freezing cold to the touch.I get a cold draft that comes down my steps making the house cold.Ive had a new roof,new windows,new doors, open cell foam sprayed in the attic rafters and blown inn cut up newspapers insulation on the attic floor.
The roofer put in every 2ft. or so a 2″ hole in the soffits for air flow on both sides of my Cape house. 2 years went by and my house was still cold wit this draft.The roofer came back 2 years later and plugged all the 2″ holes in the soffits on both sides of house with pieces of fiber glass insulation.I still have this cold draft coming down the stairs.
I had another insulating company blow close cell foam in the dormers and the floors in the knee walls.Still I have a draft of cold air coming down the steps.
Upstairs bath vent is insulated well.
Can you help?
What should I do?
Also,
Was it a mistake to put down carpet in the knee wall areas?
Could that be trapping the cold air?
Bob
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Replies
It sounds like you have air leaks. They could be anywhere. You need to find them and seal them.
If you can feel a draft, you should be able to walk along the wall with a source of smoke -- an incense stick is the usual thing -- and isolate where the air is coming in.
Thanks DC,
Definitely air leak or leaks.
I will try with the smoke.
Do you think I should seal all the soffit holes with foam on each side of house?
..and should I remove th carpet from the knee walls space?
If DC comes back to this thread he will probably give you better and more advice than me. I'd say do the smoke test but hold off on sealing the soffits. I doubt the carpet is the issue. The soffit ventilation may be providing important ventilation to the unheated parts of your attic and blocking them may cause other problems. Most likely you'll find leaks elsewhere, independent of that desirable attic ventilation.
As far as the dormers, it sounds like important spots were missed for insulation, which suggests other shortcuts might have been taken. Do a search here on the site for "attic knee wall insulation" and a number of useful articles will show up. Read through them and that should give you some ideas what should be done. Then you can look at the work at your place and perhaps identify overlooked areas.
Here is an excellent article that describes the best way to insulate and air seal the attic behind a knee wall:
https://www.greenbuildingadvisor.com/article/insulating-behind-kneewalls?oly_enc_id=9907F5428378J3D
I had a little trouble understanding you description of the existing conditions, but I think I mostly understand. First of all, is the roof vented or unvented? I assume that it is vented if the roofer drilled holes for soffit vents? If unvented, wouldn’t the holes just go right into the foam insulation? If it’s unvented, and if the foam does not completely fill the rafter bays, this could be a source of your air leaks. Fiberglass insulation is air permeable, so stuffing the holes with air permeable insulation will not prevent outside air from entering. The article that I linked to above advises to use closed cell spray foam for an unvented roof. I thought you might be getting air leaks from the rim joist, but then you said that you had closed-cell spray foam installed on the floor of the triangular attic. Unfortunately, this is mostly completely useless, except that hopefully the rim joist was completely air sealed with the spray foam, although that is not known. As far as the cold dormers, there are many possible locations for air leaks around the dormers. I’m also confused as to where the cellulose insulation is located. Is that in the attic above the second floor ceiling? Is so, then that attic is most likely a vented attic, perhaps with gable vents(?). Are there ventilation channels on the sloped ceiling between the knee wall attic and the upper attic? If not, then there is no point in having soffit vents or a vented knee wall attic because the ventilation air will not have anyplace to escape. I think the best advise would be to get a blower door test with smoke so that air leaks can be definitively located and dealt with. Infrared photography might also be useful. Finally, the carpet has no bearing whatsoever on any of this.
Additional reading:
https://www.greenbuildingadvisor.com/article/insulating-a-cape-cod-house
https://www.greenbuildingadvisor.com/article/using-smoke-to-find-air-leaks
https://www.greenbuildingadvisor.com/article/blower-door-directed-air-sealing-2