Fwiw ... R20 conductance is .050 ... 95% efficient, and R28 conductance
is .036 ... 96.4% efficient or not much of a difference. And you didn't
say but just in case, a ridge vent is the perfect partner for that
raft-R-mate (although I would think if the fiberglass is installed
carefully the raft-R-mate should not be required). And of course a
completely sealed vapor barrier.
With a cathedral ceiling you get one chance to do it right.
Put in the max. Stuff in 6" of fiberglass then add as much
foam below as you can afford, then add a bit more.
I'm in Manitoba, Hydro is recommending R50 now.
I put in R60 two years ago. Yes R-Six-Zero.
Temps. around here drop below -40 Deg F. in the winter.
With a good fire going in the wood stove the inside temp.
near the ceiling peak is probably 80 or 90 deg. F. even with
a fan going. A lot of heat to keep snow off the roof.
As for economy and the 95% - 96% boys, where were they years
ago when R12 was enough, then R20, R40.
The cost of heat is only going to go up. The bean counters will
whine today because "You won't get the return for your money"
then tomorrow they will cry "It costs so much to heat, put in
more insulation". In reality that bunch doesn't know their ass
from a hole in the ground.
If you are building to sell and make a quick buck then go bean
counter minimum, otherwise think 20 years down the road. If not
for yourself then for your kids if you want them to be able
to afford the place.
Lots of ventilation. I put in metal ridge vent right across all
One added bonus of the metal ridge vent is that birds don't
like to land on the things. they stay away from my roof and crap
all over my neighbors roof (ridge vent covered with a shingles)
Seagulls, crows etc. the stuff covers half the top of his roof
and hardly a drop on mine .
By the way I built that place, I hired out the foundation,
shingles and HVAC, the rest I did with help from family and
friends, not a fricken bean counter among them. :) :) :)
and as they say "Put my money where my mouth is".
How strange. Why would the ceiling be so hot with a ceiling fan going?
Is the stove red hot, with no insulation in the house walls? :-)
You want lots of R1/inch snow on the roof, no?
How can it melt with that 2" air gap?
Nick, you seem to have no experience heating a house in a cold climate.
of course the heat rushes to the peak of his vault! ever heated a
house with a wood space heater? an air space alone won't stop snowmelt
either. that one has been proven time and again.
Don't bother Nick. He's busy trying to solve some partial differential
equations to calculate how hot it theoretically should get at the top
of a vaulted ceiling, instead of actually having one and knowing it
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