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What is the proper installtion technique for blown insulation without soffit vents?

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I have a Michigan Home built in the 1950's with very little attic insulation. The attic rafters are only 4 inches in height and have vermiculite insulation up to the top of the 2x4's. also the attic does not have soffit vents. It does however have two large gable vents on each side, apporx. 12" x 24" and 5 round vents on the top of the attic.

I'm considering adding addtional blown insulation to the attic (around 12 inches), since I don't have soffit ventilation, should I blow the insulation right to the attic walls? Or should I still use rafter vents? The slope of the roof is very low, and i'm unsure if I would even be able to get out far enough to install the rafter vents.

asked in Attic Area by obricko (120 points)
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1 Answer

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Hi Obricko,
Since you are in Michigan, because of the cold winters, there should be some space left between the insulation and the roof decking. With gable vents installed there’s no need for soffit vents, however, if you fill the sides of your attic with insulation all the way up to the rafters / roof decking condensation may start developing when temperatures drop below freezing. 
What you can do, instead of installing rafter baffles, is to get some blanket insulation (un-faced), cut  12”-24” long pieces and slide it (push it with a stick if unable to crawl that far) towards the corner where the attic’s floor meets the roof framing. That way you can better control the air gap. Whatever area you have left can be filled with blown-in insulation. 
A couple of tips... be extremely careful with that vermiculite insulation because it might contain asbestos. It will be impossible not to disturb it while working there and pushing those pre-cut pieces so make sure to wear an appropriate respirator mask (not just a dust mask) and eye protection!.
Always assume that it contains asbestos unless it was already lab tested and proven otherwise! Wear bosy protecting suit / gloves and seal off the house access to prevent any possible contamination. Wait for a cool weather.
Let me know if have more questions, just click “comment” below
answered by darekrudy (21,730 points)