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Posted by on January 23, 2008, 9:00 pm
On Jan 23, 8:52 pm, websu...@cox.net wrote:
>
>
>
>
>
> > > > 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
> > > > insulation.
>
> > > > 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.
>
> > > > Thanks,
> > > > John
>
> > > I think venting is important but what abour SIPs construction, Ive had
> > > chipmunks in my foam and ive heard carpenter ants nest as well.
>
> > 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.
>
> > John
>
> 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,
> misperception, whatever...
>
> 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
> batts.
Trust me, Tiger Foam is the best around. I fixed my 3 car garage last
fall and this winter its been soooo warm inside it's unreal.
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