spray foam insulation


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Old 02-16-15, 11:16 AM
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spray foam insulation

I bought a house in the north suburbs of Chicago about 2 1/2 years ago. Over the past two winters, we have had ice damming along a few parts of our roof. I would like to better insulate the roof. There is no attic below the concerned areas of the roof.

I had an insulation contractor come out today. He wants to use spray foam to fill in the space between the existing dry-walled ceiling and the existing roof. I have been trying to research this technique, but I have had little success finding any answers.

Does anyone have any thoughts about this plan? Will be effective? Will be safe for the roof?

Thanks
 
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Old 02-16-15, 11:25 AM
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While I go looking for articles, what is up there now for insulation, ventilation, and heated/conditioned space.

Bud
And welcome to the forum!
 
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Old 02-16-15, 11:33 AM
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At this point, we don't know what is up there. Whatever it is, it has not been effective in preventing heat escape and ice dam formation.

Thanks for your help and the welcome.
 
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Old 02-16-15, 11:51 AM
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ckay, I still need more details.

1. <There is no attic below the concerned areas of the roof.> This would seem to be a finished sloped roof as you also mention drywall. IMO, it would be rare for there to not be some insulation in there and subsequently trying to fill that space with spray in foam can be less than desirable.
2. Is there ventilation, soffit vents, ridge vents, roof vents, or gable vents? Again, doubtful it is an unvented roof assembly, which is what you/they are suggesting.
3. Is the floor layer below this an insulated ceiling?
4. Is this space heated and/or cooled. If this is conditioned space, then the proposed roof assembly should meet minimum insulation requirements if for no other reason, they are bare minimum.

Here is a link for some reading, to quote:"In recent years, most building codes have begun to allow the construction of unvented insulated sloped roof assemblies. Many such roofs have failed over the years, however, so it’s essential to get the details right." from:
How to Build an Insulated Cathedral Ceiling | GreenBuildingAdvisor.com

Bud
 
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Old 02-16-15, 12:05 PM
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In our area, they are doing this same thing on many new homes or remodels where adequate insulation can't be achieved by other means... usually because of the thickness of the rafters and joists at the top plate or on cathedral ceilings. They opt for a non-ventilated closed roof with maximum r-value over a ventilated roof with substandard r-value.

Whether or not this helps solve the ice damming is unknown, however since the space available may not be sufficient to create the temperature difference needed to keep the roof deck cold.
 
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Old 02-16-15, 02:00 PM
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You don't need much. I have 3" of CCSF under my roof now and I haven't had any ice dam issue this year. I had one area on my roof that was always a problem.
 
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Old 02-16-15, 02:08 PM
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That's pretty impressive drooplug...

I guess what I meant by "whether it helps or not..." was that the op didn't say anything about the size of the space needing to be filled, the distance from top plate to roof sheathing, or anything about the existing insulation.

3" to fix your problem is pretty impressive, though. That's encouraging.
 
 

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