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demandrew 12-19-2011 10:16 PM

Insulating walls with varying depth
Hi all,
I'm currently engaged in my first major room renovation (the kitchen) and I'm now at the pre-insulation stage. For a number of reasons, which we can discuss later if you like, I have two walls with two different and slightly akward depths to insulate, and one ceiling with a depth that changes from one side to the other. So the question is, how would you insulate these areas?
Wall #1: There is approximately 4.5inches of room to insulate. Unfortunately larger than the standard 3.5 pinkpanther, but not quite big enough for the 5.5. Would you buy 5.5 and squish it in despite the loss in r-value owing to it being squished, or put in a layer of rigid foam first and then the standard 3.5inch on top?
Wall #2: There is approximately 2.5inches of depth. So a similar question goes: squish in 3.5 and lose some r-value or pack it with multiple layers of rigid foam (if I can afford it)
Ceiling: the depth in the ceiling goes from about 5inches at one end to almost a whopping 11inches at the other. Any thoughts with this one??
As always, thanks for your help and advice.

Windows on Wash 12-20-2011 08:15 AM

Where is the home?

Climate region will somewhat dictate the recommendations on foam.

Rigid foam is a great option and its R-Value remains constant.

Regardless of insulation schedule, you want to make sure that the wall assembly (exterior wall in this application because you can access it) is air tight.

shazapple 12-20-2011 08:52 AM

I have an older house and the walls were true 2x4 with 0.5" strapping, so effectively they were 4.5". I squished 5.5" insulation into the space. Owens Corning has a compression chart here that shows a R21 batt would be somewhere around R18. The time/cost of rigid insulation was not worth it for this wall.

For your 2.5" wall, I would sister the studs to give you more room. That would probably be cheaper than rigid insulation as well.

The ceiling depends on if it is a roof, in which case it will need ventilation. To gain more room you could slope your finished ceiling to get 11"+ along the entire section.

WoW is correct on all points, region definitely helps us and good air sealing is a must.

demandrew 12-20-2011 01:07 PM

Thanks for the replies!
I live in Toronto, so it does get a bit chilly here in the winter and rather hot in the summer. The kitchen is on the top floor, so it gets the worst of it in either season.
I think I will just compress 5.5inch into the 4.5inch space, and likewise squish some 3.5inch into the 2.5 space. The reason I don't want to sister the studs and bring the wall out farther is because the room is already tight, and to lose another inch or so, as little as it sounds, would be detrimental to my overall plans. The 2.5inch depth was actually determined by me to be the maximum extension possible from what was originally about a 1inch space.
The kitchen is on the top floor, so I guess that would make the ceiling the roof. I hadn't fully considered that it would need to be vented. I've heard of venting attic ceilings, but that's when you have access to the soffits which I don't think I do in this case. The exterior walls are brick (likely two layers) and then there are two interior walls. The ceiling butts up against the brick where it is present so I'm not too sure where or how I would ventilate. Any advice here?

Windows on Wash 12-21-2011 07:31 AM

4.5" of fiberglass is wholly inadequate in that region.

I would look at investing in rigid or spray foam. You can only do this it right...or "Make it Right!" for the Canadian folks (in honor or Mike Holmes). :laughing:

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