Latest Discussions : Basement & Foundation

suggi1

06:10PM | 11/15/08
Member Since: 09/03/07
32 lifetime posts
A mold inspector told me to get this new company to completely seal off the attic with some kind of foam -- no vents at all - gable, ridge, soffit. He said it would save a tremendous amount on heating and cooling bills and would not encourage mold. Somehow, this does not seem right as I thought attics were supposed to breathe and not be all sealed up with no ventilation. Also, how would you know if you had a leak. It seems mold would actually like this type of attic.

If anyone has any thoughts on this please inform me. Thanks.

Billhart

05:24AM | 11/16/08
Member Since: 04/25/05
1915 lifetime posts
What you are talking about is call a "hot roof".

www.buildingscience.com

It has good design and but one needs to be a lot more careful in the design and installation than a the more common vented attic.

In general it is used in too cases Vaulted ceilings or where you have HVAC equipment or ducts in the attic.

Or possibly where you have plans to latter finish off the attic.

In general it is not used for retrofit.

Don't know mold inspector would suggest this. If you have mold in the attic then that should be fixed by attic venting and making sure that any stove or bath fan venting extends outside the house and not in the attic.

suggi1

12:36PM | 11/16/08
Member Since: 09/03/07
32 lifetime posts
Thanks - we do not have mold in the attic now and had the gable vents closed off (per inspector 2 years ago) - just have soffit and ridge vents. We do have an a/c unit and ductwork in the attic and the foam would not be on the floor just all over elsewhere. We o not have cathederal ceilings.

However, from your answer it seems you think it could be done but my concern is -- what if you ever got a roof leak???

If you were going to construct a house at some point is this something to consider?

Billhart

02:16PM | 11/16/08
Member Since: 04/25/05
1915 lifetime posts
This is a big area of discussion between contractors, insulators, and building science people.

First there are two types of insulating foam used.

Open cell and closed cell.

The open cell will let water through. And it is is lower R value so that it take more foam.

And in the very coldest climates (I think colder than 7500 heating degree days) it requires a vapor retarder, but that can be handled by painting it.

But in reality roof leaks or not that much of problem if the roof is done correctly with the right flashing etc.

I am not sure what I would do.

On new construction I would do anything possible to keep HVAC and ducts out of an unconditioned space. Either put them in different place, foam the roof or use SIPS for the roof.

The more cutup a roof the more possibility of leaks.

I would have to do some shopping before deciding to do that on a retrofit.

And part of that would be getting a quote from a GOOD HVAC contactor (find one that will do a duct blaster test) to seal and insulate the ducts and the HVAC where possible.

Sorry, but I can't give you an absolute yes or no.


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