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Matt Kenner Posted: Oct 13, 2009 04:42 PM	unvented attics Mason, Ohio goes by the IBC (in ohio it is called OBC). Ohio uses very limited amounts of the IRC. Do you know of anywhere in the IBC I can find provisions for unvented attics? I know it's in the IRC806.4 but I can't find anything in the IBC. Thanks for your help.
mason Posted: Oct 13, 2009 04:53 PM	I am having trouble finding the section in my 2007 supplement and in my 2009 IBC code book as well. Let me work on it tomorrow and provide the answer. It may be in the IBC structural section of the 2009 code book. I'll check it there.
mason Posted: Oct 14, 2009 07:55 AM	I remember now. Unvented attics were approved in the 2004 supplment in the IECC Chapter 8; Building Design for Commericial Buildings: The section 802.1.2 MOisture Control had the following language "All framed walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder having a permeance rating of 1 perm or less, when tested in accordance with the dessicant method using procedure A of ASTM E -96. The vapor retarder shall be installed in the warm-in-winter side of the insulation." Exceptions: 1. Buildings located in Climate Zones 1-3 ... 2. In construction where moisture or its freezing will not damage the materials. 3. Where other approved means to avoid condensation in unventilated framed wall, floor, roof and ceiling cavities are provided." This language adopted by the IECC automatically pertains to the IBC codes. However, it does not neccesarily pertain to the IRC. So, if they are using the 2004 supplement you are covered. Now going to 2006 code books: The IECC Chapter 8 was deleted and the moisture control language allowing unvented attics was moved to the following sections 402.5 which represents residential construction and section 502.5 which represents commercial construction. Again, the IECC language is dominant when using the IBC. "402.5 Moisture control. (Mandatory). The building design shall not create conditions of accelerated deterioration from moisture condensation. Above-grade frame walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder. The vapor retarder shall be installed on the warm-in-winter side of the thermal insulation. Exceptions: 1. In construction where moisture or its freezing will not damage the materials. 2. Frame walls, floors and ceilings in jurisdictions in Zones 1 through 4. (Crawl space floor vapor retarders are not exempted.) 3. Where other approved means to avoid condensation are provided. 502.5 Moisture control. (Mandatory). All framed walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder having a permeance rating of 1 perm (5.7 × 10 –11 kg/Pa • s • m2) or less, when tested in accordance with the dessicant method using Procedure A of ASTM E 96. The vapor retarder shall be installed on the warm-in-winter side of the insulation. Exceptions: 1. Buildings located in Climate Zones 1 through 3 as indicated in Figure 301.1 and Table 301.1. 2. In construction where moisture or its freezing will not damage the materials. 3. Where other approved means to avoid condensation in unventilated framed wall, floor, roof and ceiling cavities are provided I am still looking in the 2009 IBC and IECC for the moisture control sections. I will post them when I find them. It might take a while because I have to get to some other projects today. But, if your code official is using the 2006 book, this should cover you.
Matt Kenner Posted: Oct 19, 2009 08:27 AM	Thank you Mason. I appreciate the time you put into this response. Matt

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Matt Kenner

Posted: Oct 13, 2009 04:42 PM

unvented attics

Mason,
Ohio goes by the IBC (in ohio it is called OBC). Ohio uses very limited amounts of the IRC. Do you know of anywhere in the IBC I can find provisions for unvented attics? I know it's in the IRC806.4 but I can't find anything in the IBC. Thanks for your help.

mason

Posted: Oct 13, 2009 04:53 PM

I am having trouble finding the section in my 2007 supplement and in my 2009 IBC code book as well.

Let me work on it tomorrow and provide the answer. It may be in the IBC structural section of the 2009 code book. I'll check it there.

mason

Posted: Oct 14, 2009 07:55 AM

I remember now. Unvented attics were approved in the 2004 supplment in the IECC Chapter 8; Building Design for Commericial Buildings: The section 802.1.2 MOisture Control had the following language
"All framed walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder having a permeance rating of 1 perm or less, when tested in accordance with the dessicant method using procedure A of ASTM E -96. The vapor retarder shall be installed in the warm-in-winter side of the insulation."

Exceptions:
1. Buildings located in Climate Zones 1-3 ...
2. In construction where moisture or its freezing will not damage the materials.
3. Where other approved means to avoid condensation in unventilated framed wall, floor, roof and ceiling cavities are provided."

This language adopted by the IECC automatically pertains to the IBC codes. However, it does not neccesarily pertain to the IRC. So, if they are using the 2004 supplement you are covered.

Now going to 2006 code books: The IECC Chapter 8 was deleted and the moisture control language allowing unvented attics was moved to the following sections 402.5 which represents residential construction and section 502.5 which represents commercial construction. Again, the IECC language is dominant when using the IBC.

"402.5 Moisture control. (Mandatory). The building design shall not create conditions of accelerated deterioration from moisture condensation. Above-grade frame walls, floors and
ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder. The vapor retarder shall be installed on the warm-in-winter side of the thermal insulation.

Exceptions:
1. In construction where moisture or its freezing will not damage the materials.
2. Frame walls, floors and ceilings in jurisdictions in Zones 1 through 4. (Crawl space floor vapor retarders are not exempted.)
3. Where other approved means to avoid condensation are provided.

502.5 Moisture control. (Mandatory). All framed walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder having a permeance rating of 1 perm (5.7 × 10 –11 kg/Pa • s • m2) or less, when tested in accordance with the dessicant method using Procedure A of ASTM E 96. The vapor retarder shall be installed on the warm-in-winter side of the insulation.

Exceptions:
1. Buildings located in Climate Zones 1 through 3 as indicated in Figure 301.1 and Table 301.1.
2. In construction where moisture or its freezing will not damage the materials.
3. Where other approved means to avoid condensation in unventilated framed wall, floor, roof and ceiling cavities are provided

I am still looking in the 2009 IBC and IECC for the moisture control sections. I will post them when I find them. It might take a while because I have to get to some other projects today. But, if your code official is using the 2006 book, this should cover you.

Matt Kenner

Posted: Oct 19, 2009 08:27 AM

Thank you Mason. I appreciate the time you put into this response.

Matt

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