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Un-ventilated attic space

Un-ventilated attic space

Un-ventilated attic space

I am working on home gable roof repair in Canada in a very cold climate region.
The attic space had soffit ventilation, however the assigned contractor had insulated the attic space using spray-foam and covered up the soffit ventilation area.
So, now, I have an airtight attic space with no ventilation what so ever.

Is this a problem for moisture damage/ice damming on the roof? My thought is that if you assume that the spray foam insulation provides an air barrier and air-tight space performance, then I don't expect warm air to travel up to the attic space and cause moisture damage/ice-damming during the winter months. Would ventilation therefore be required?

Are there any references published on the performance of air-tight attic spaces?

Thank you,

RE: Un-ventilated attic space

Ice dams may be an issue, although less so with it being well insulated. The bigger issue with unheated, unventilated spaces in cold climates is usually condensation, and the associated ceiling water spots, rotting roof sheathing, and mold. The spray insulation may prevent the roof sheathing from rotting, but you could still have issues with damp or dripping ceilings and mold.

Rod Smith, P.E., The artist formerly known as HotRod10

RE: Un-ventilated attic space

Thank you for the replies Compositepro and BridgeSmith.

I agree, un-ventillated space will lead to lots of complication especially here in Canada.
I found this really good resource talking about this particular issue (summary of the video above !):


RE: Un-ventilated attic space

Install some gable end vents, and poke some holes thru the foam at the soffets. The sheathing will rot otherwise. The attic will get condensation on the underside of the sheathing and freeze.

Mike McCann, PE, SE (WA, HI)

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