Hi folks. My new cottage is all closed in weather tight but without
any interior finish and I'm looking at insulation options. I like the
idea of spray in foam because of the potential for rodents in batt
Question, would you spray the stuff tight against the inside of the
roof sheathing? Or would it be best to maintain an airspace against
the roof with Rafter-Mate vents or something similar, vented between
soffit and attic, spraying over that instead.
Everyone I talk to says to vent, so vent it will be. I'm also leaning
toward regular batt insulation. The place is pretty darn tight with
2x6 walls and all new doors and windows so it hopefully will be easy
to keep critters out, or to trap the few who might make it in...
heckuva lot cheaper too.
I looked into foam for our new house, but the builder was too busy to
accommodate anything different, so I couldn't. 8<(
However, the venting situation sounds like a common....habit,
Usually, a house has the blown in stuff or batts on the floor of the
attic. The space above that insulation must be vented to allow
moisture out, and to allow the attic to cool in the heat of the day
(the sun really heats up an attic).
The people who apply the foam recommended that the attic NOT be
vented, since the attic air space is now INSIDE the insulation
envelope, and therefore wouldn't get that hot in the first place. It
can abe considered as just another room in the house. Around here
(Phoenix), the attic would be much cooler if not vented (in summer),
than if it were. This all made perfect sense to me. Especially
considering that the air conditioning ducts and exchanger would be in
milder space than it is now, which would save energy and extend the
life of the equipment and ducts.
I only came up with one concern: if there is a roof leak (which there
will be, since they use cheap thin tar paper under the tiles), the
foam might hide it for a while, even if you went up periodically to
inspect the bottom of the roof.
Unfortunately, I can't speak from personal experience since I wasn't
allowed to upgrade the insulation of the house from the 1950's era
On Jan 23, 9:00�pm, firstname.lastname@example.org wrote:
foam is the way to go closed cell about R6 per inch, no need for
venting since moisture laden air cant get near the wood.
with a long lifved roof system the rubber membrame is a much better
choice than tar paper. seals all the nail holes and prevents ice dam
the foam and proper roof will cost more but reward you in a lifetime
of energy savings
Unfortunately, until we can convince the developers and mass builders
of this wisdom, it is near impossible to get them to change. They
know what they already know, and will take no risks. THEY don't pay
the utility bills for the rest of the life of the house....
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