Rafter Baffles (no soffits)

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Joined: Wed Dec 04, 2019 10:23 am

Rafter Baffles (no soffits)

Post by Longnok »

I'm in the final stages of prepping the attic in my 1928 bungalow for blown-in insulation. Currently, there is 3 inches of insulation (mineral wool) and I will be taking the total r-value up to R60. I'm in Zone 5 and in a low humidity climate at 6,000 feet. Total snowfall this season has been around 36 inches.

My house has no soffit vents, as it is a traditional Craftsman bungalow with exposed rafter tails under the eaves. The front and rear of the house is fully gabled and has a gable vent on each end (front and back). I will not be adding soffit vents. I have air sealed all ceiling penetrations in the attic following the guidelines by Building Science and energystar.gov.

The question: Do I need rafter baffles?

I cannot find any definitive information for my situation, although I know it is no unique. Obviously, with R60, insulation will be touching the underside of the roof sheathing and my concern would be moisture accumulation, although things around here dry out quickly. I have Nash and Litchfield's books, as well as, read several papers by Lstiburek (Building Science). Lstiburek eludes about needing separation of insulation from the roof sheathing, but nothing definitive in relation to a house with no soffit vents.

Thoughts? Thanks!

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