I have a storage area in a bedroom over our garage. The area has
soffits to allow the area to breathe. My question started when I
visited the home and garden show this past weekend. A couple of spray
foam insulation guyes said that I could close off the soffits and
spray some foam insulation in there for a lot better weather
proofing. Of course, I cannot help but wonder if it is safe to cut
off the breathing in the storage area. If it can be done, is it safe,
and could it be done with batts of fiberglass insulation and
sheetrock, or do I have to use spray foam insulation, then sheet rock
over it. If it is safe and can be done, then I would have done it a
long time ago because the air leakage from the bedroom to the storage
area is terrible, and is changing the room in the bedroom by at least
a couple of degrees
I'd bet it's more than a couple of degrees. With spray foam people
are frequently astounded by how little heat needs to be applied, how
much quieter the attic room is, cooler in summer, etc. Good stuff.
Unvented attics cannot be done with anything other than spray foam. A
perfectly continuous, unbroken amount of insulation must be applied,
and there must be a perfect vapor barrier. The powers that be are in
the process of updating construction codes to incorporate unvented
spray foamed attics and living spaces under the rafters. If the
correct amount of spray foam is applied (Google spray foam rafters dew
point for more information on that), then there will be little problem
as long as the roofing is kept in good or better condition.
Code requires that foam must be covered, and if it's a living space
drywall is the obvious choice. There are some products that might
satisfy your local code, that come in rolls that are reflective on one
side, have a fiberglass mesh embedded and are barriers to ignition.
Spray foam is very expensive for a storage room (do you want a warm
storage room, or just a warmer bedroom?). Can't you just insulate the
wall between the storage room and the bedroom? Spray foam might be a
good choice for that, but rigid foam board might be good enough and
much cheaper and DIY (if the wall itself is not already insulated,
that's an easy fix too, just rip of the sheetrock or sheathing on the
storage room side and install batts).
Some cities (including mine) won't allow a spray foam installation
that eliminates venting from soffit to ridge (every bit of research
I've seen says this is overkill, but the inspectors haven't all caught
up yet). Maybe that won't apply in a storage room, but it might do
since it's still part of the house. Instead you have to run chutes
from soffit to ridge (that part's an easy DIY and not expensive)
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