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jarylu 05-21-2012 07:43 AM

cape style home insulating needs
Ive got a cape built 1945 in upstate NY. The code calls for R49 here. There's no way I can get that much insulation in the storage space behind the knee wall much less above the ceilings. Here''s what's happened so far:

1994 roofer installed ridge vent (why I can't say).
NY Energy Program did review in 1997 and suggested improving insulation in attic area. Floors behind knee wall had cellulose blown in (R19 at best). Knee walls have R19 installed (backwards--kraft paper facing out rather than against wall with heat) - again, don't ask me why..
Above ceiling area from knee wall to peak is cellulose blow in insulation (settled over time).
From soffit to knee wall is covered with rigid vent for air space at roof and then R21 insulation over it.

Heres the thing. I've got ice dams every year in the rear of the house. Front is fine it gets sun. There are holes in the soffit and it seems to be getting air but not sure if its moving above knee wall (at ceiling).

One issue: gutter may not be angled properly.
Question: I can't seem to get to R49...or am I missing something?
Is there adequate air flow? There is no gable vent...should there be?

The bedrooms upstairs have 1/4 "sheetrock". Not heated - in fact, we use space for cold storage (60 degrees). Yet, both rooms are hot -- as is the attic now (late May). It doesn't seem to be helping.

Oh,, and I read that fixtures, wiring, etc. should have air gaps plugged. That didn't happen..

Thoughts? Suggestions?

Gary in WA 05-26-2012 05:16 PM

You need to air seal the attic and bring insulation up to minimum Code for location. If the exterior wall top plates are above the ceiling line, you need to seal them from delivering warm air to the junction. Ice dams:

Stack effect:

Finding air leaks:

Getting enough attic ventilation/insulation with existing sloped ceilings can be a problem. Have you looked into conditioned attics?


AGWhitehouse 06-01-2012 03:08 PM

You need to re-roof if you expect to get anywhere near R-49 with a cape. Once the roof is stripped to bare substrate (plywood) you'll want to install vented nailbase panels which look like this:

They are typically a polyisocyanurate foam board bonded to blocking for an air space and then a layer of either osb or plywood. Depending on the manufacturer you can get varying insulation, air space, and plywood thicknesses. Once those are installed you lay down new shingles.

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