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Community and Q&A

Insulating Low-Slope Roof in Hot-Humid Climate

user-1148246347 | Posted in General Questions on

I am a homeowner in the Southeast (mild winters and hot, humid summers) and am looking for guidance on how to approach issues of ventilation and insulation in our mid-1960s, low-slope roof home. I’ve really struggled to find contractors who can properly advise me and to be honest, just don’t have the knowledge or expertise to navigate the more technical articles on this otherwise extremely useful website.
As we try to move towards a more energy efficient home, we are encountering many of the problems that I’m seeing described here– things like ceiling and wall condensation after sealing gaps between our cathedral ceiling and roof assembly, as well as small gaps around can light fixtures below the attic.
In addition to these concerns, we had our roof replaced about 5 years ago by a contractor who didn’t have as much experience with low-slope roofs as we thought. The roof that was installed, a rolled-out MuleHide product, seems to be holding so far, but does not appear to be vented anywhere except through some soffit vents off the attic.
The blown-in insulation in our very small attic (under one half of the roof, while the other half covers a cathedral ceiling) is old and has welcomed lots of critters. It’s time to replace it, but I’m unsure of how we can effectively insulate the attic without compromising roof ventilation.
The attic gets very hot in the summer and the walls below it start to sweat. I hesitate to insulate the entire attic space with the spray-foam applications I see advertised by local contractors because I worry that this might make the roof susceptible to moisture, especially if it’s not well ventilated.
I was wondering if it would be possible to apply spray-foam insulation to just the parts of the attic that are in contact with the living space (the floor and a wall on one side). This would help mitigate the temperature differential in the summer between the hot attic space and the air-conditioned living space directly below. At the same time, it would leave the attic ceiling uninsulated but allow the air to move freely between the attic and the roof …I think.
I would appreciate any guidance or recommendations about this plan or any alternatives. Thank you!

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