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radgumbo 12-05-2010 07:02 AM

Shed roof addition question/advise
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I finished a (shed roof) addition on the back of my house which measures approx. 16' x 39'. I came off the back of my house and installed 2 x 6 rafters with a low pitch of about 2/12. (The span is supported by post & beam). Since, I was adding to an existing structure, I kept the roof pitch the same but wish now I had raised it slightly.

In any case the interior side of the roof/ceiling is where I want to use spray in foam insulation to eliminate any chance of a condensation/moisture problem. When I installed the roofing I used a waterproof membrane, 30# felt and roll asphalt roofing. I plan on going over this with metal roofing in the next couple of years. I'm concerned about ventilation through the rafters. I have soffit vents on the back side and the rafters run into the space that the original roof and the new roof created...with vents on the two opposing sides. If I use spray foam insulation @ 1-2" thick & fill the remaining void with fiberglass insulation won't that eliminate the need to have any ventilation at all (between the rafters)? Keep in mind, the waterproof membrane on the roof itself.

I had initially installed R19 paper faced insulation with styromfoam channels in the ceiling/rafters and noticed mildew building up so I removed it and began installing R13 insulation to allow more air flow thru the rafters. Photo 1 shows the first insulation and the last 3 the 2nd insulation. Additionally, I used radiant foil over the 2nd insulation and then learned of the spray foam...what do to think?

radgumbo 12-05-2010 09:24 AM

How come my editing (mispelled "question") isn't working....geez, is it a site glitch?

seeyou 12-06-2010 05:33 AM

Closed cell or open cell spray foam?

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