Tiger Foam against roof sheathing ?

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
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I think venting is important but what abour SIPs construction, Ive had chipmunks in my foam and ive heard carpenter ants nest as well.
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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
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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.
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On Jan 23, 8:52 pm, snipped-for-privacy@cox.net wrote:

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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On Jan 23, 9:00�pm, snipped-for-privacy@gmail.com 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 damage
the foam and proper roof will cost more but reward you in a lifetime of energy savings
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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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On Jan 24, 9:04�pm, snipped-for-privacy@cox.net wrote:

might be time for mandatory building code insulation upgrade.........
good for the buyer, good for the environment. good for resale value.
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