# Insulating under part of my Flat Roof



## Hushpuppy (Feb 10, 2006)

Hi,
We're having a contractor gut and rehab our kitchen and bath. The ceiling is being torn out, as well. When we replace the ceiling we have the opportunity to replace the insulation between it and the roof. As this is an old house, much of the roof has little if any insulation under it.

It's an old building, about 80 years, with 2-3 feet between the ceiling and the bottom of the roof. Also, it's a flat roof and the kitchen is in the back (at the bottom of the slope).

And we live in Chicago.

So the question is, if the kitchen is insulated will we run into problems with snow melting on the roof in the front of the house, and the runoff getting stopped by the snow not melting over the colder-and-more-insulated kitchen? Thus the water will puddle and eventually leak. We're a little worried about this. Thanks.


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## AaronB (Jan 29, 2005)

With a posotive slope of at least 1/8" and a proper low slope roofing system installed, you shouldnt have a problem. Go for it. Make sure to install a vapor retarder between the insulation and drywall ceiling.

Hope this helps.


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## Bonus (Aug 25, 2005)

Not to hijack this thread, but what is the accepted method of ventilation in a roof like this, Aaron? Is there one?


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## AaronB (Jan 29, 2005)

Generally, you should not need ventilation in an assembly like this as there is not usually an attic space to build up heat, and there should be a vapor retarder between the insulation and ceiling. Occasionally, you will have an air space between the ceiling and roof deck, but most heat build up will come from the outside. Reflective roof coatings can do the trik most times to take care of this. Even when there is a cavity between the ceiling insulation and the roof deck, there is no intake ventilation, so exhaust ventilation would be useless for venting heat. If you do have intake vent, there are one way roof vents available, and also curb type vents with a sheet metal hood, but once again, this is rare.


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## Bonus (Aug 25, 2005)

Appreciate the info, tks.


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## Hushpuppy (Feb 10, 2006)

*Thank you*

Thanks for the replies! I feel more confident going forward. Our contractor was aware of the need for the vapor barrier, so I feel better that he understands what to do.

Thanks again.


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