Insulating Unvented Cathedral Ceilings

 
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Old 06-10-2017, 04:52 PM   #1
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Insulating Unvented Cathedral Ceilings


I got called to look at a house that the USDA is funding the money to do some repairs, it is for low income reasons. Anyway, the back part of the house is an ad-on, so the roof rafters and ceiling joists are the same, 2 x 6's. The instructions by the USDA says it has to be insulated to a r-33, which I know isn't going to happen.

My question is - Is there going to be a problem using fiberglass bat insulation in the 5.5 inch space?

These people are not rich, hence the USDA loan, I wonder if I should bid to put in sister joists, 2 x 14 to get a r-33?

Edit - btw it is a 25' x 14.5' room.
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Old 06-11-2017, 01:12 AM   #2
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Re: Insulating Unvented Cathedral Ceilings


You can get that rating with rigid foam insulation products.

You don't really give enough information on the house to make a definite recommendation on a product though.

Now depending on the application and the local Authority Having Jurisdiction (AHJ), the climate zone and if the addition was permitted previously or not you may indeed be able to get away with the R-19 FG batt insulation.

Andy.

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Old 06-11-2017, 11:16 AM   #3
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Re: Insulating Unvented Cathedral Ceilings


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Originally Posted by ScipioAfricanus View Post
You can get that rating with rigid foam insulation products.

You don't really give enough information on the house to make a definite recommendation on a product though.

Now depending on the application and the local Authority Having Jurisdiction (AHJ), the climate zone and if the addition was permitted previously or not you may indeed be able to get away with the R-19 FG batt insulation.

Andy.
Thank you, I understand. This is N Texas, out of city limits so no special codes, probably was not previously permitted and from what I saw does not have insulation in it now.

My main concern is it not being vented and condensation developing and causing further damage and mold. As far as the r vallue goes I am just going to call the USDA on Mondayt and discuss if that 33 has to be met.
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Old 06-11-2017, 02:31 PM   #4
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Re: Insulating Unvented Cathedral Ceilings


If there are no codes to comply with then there are no codes to comply with.

I might suggest using about two inches of foam board directly attached to the underside of the deck in the bays then fill the rest with FG batts.

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Old 06-11-2017, 08:04 PM   #5
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Re: Insulating Unvented Cathedral Ceilings


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If there are no codes to comply with then there are no codes to comply with.
OTOH, he has to meet the lender's specs if he wants to get paid, code or no code. If he can talk the USDA into lowering the spec, better get it in writing.
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Old 06-11-2017, 11:59 PM   #6
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Re: Insulating Unvented Cathedral Ceilings


It is so weird to me that the USDA United States Department of Agriculture is funding a project and that they have requirements for the house.

Very strange, does that actually happen?

Andy.
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Old 06-12-2017, 07:16 AM   #7
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Re: Insulating Unvented Cathedral Ceilings


Been going on for quite some time; it was originally mostly to help poor farmers. Decent summary here:

http://www.ruralhome.org/whats-new/b...-programs-usda

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