unvented attic | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Author	Comments
Timothy Johnson Posted: Dec 26, 2007 06:45 PM	unvented attic I am installing full envelope on new house in Brandon Ms. The inspector is using 2003 Int. Res.code book and it is not showing any allowance for unvented attic .I am using .5 lb foam.Can You email me a copy of a new code or codes that can help.City of Brandon has never had a foam insulated house and are requiring more info before allowing home to prceed
mason Posted: Dec 29, 2007 09:33 PM	You can download the 2007 IECC Supplement at this link. http://www.iccsafe.org/cs/codes/2007-08cycle/2007Supplement/index.html The section is 402 and 502 that discusses unvented attics.
Derek Martz Posted: Mar 05, 2008 09:17 PM	Yes, Mason steered me onto a section in code that has a supplement added in 2007, which no allows for unconditioned attic, however my inspector told me that Pa does not acknowledge supplements, there fore I was required to add a supply and return in my attic. It meets code but will be removed as soon as I have occupancy, and besides the supplement will be added in the next code revision. So if your state doesn't allow supplements, then put it in and take it out later or just close it. Remember, if your attic has an access hatch and accessible then you need to have a 15min ignition barrier over your foam. Basically, you cannot see any foam after house it finished. I went through all this in Pa because no homes in my area where foamed either, and the inspector was following the written code to a "T".I'm trying to find a intumescent coating to cover my foam, but becoming increasingly difficult, so i will have to use another form of ignition barrier.
mason Posted: Mar 07, 2008 07:43 AM	Unvented attics were approved in the 2004 supplement and included in the 2006 ICC code books. They were modified in the 2007 supplement. So, if your area is using 2006 ICC code, then unvented attics are acceptable. If they use the 2003 code, they are not.
David Kang Posted: Mar 11, 2008 05:59 PM	Ahhh....no mason, that's not quite correct. The code allows any code official to accepyt anything he deems "better" than the code requirement. The code is a minimum standard, not a set of rules. The inclusion of the Unvented Attic assembly in the 2006 IRC (arguably in the addendum) INFERS it is an improvement....logic dictates that it is a better system. The code official has the right to accept it if he is so inclined.
Darren Gomez Posted: Mar 12, 2008 01:23 AM	Please correct me if I'm wrong. The supplement allows for closed cell 1.5-2.0 foam. Does it acknowledge open cell foam at all or did I read that wrong. Is open cell foam allowed based on ICC codes?
Posted: Mar 22, 2008 11:32 PM	Was told that using an unvented attic was counter productive because I would be heating the attic space and moving the thermal barrier to the roof line?? Also, that the foam on the under side of a slate roof with open batten. Seams would allow moisture to leech beneath slate shingles and dissipate through the open batten and would have no where to go essentially rotting the batten board.
mason Posted: Mar 23, 2008 11:07 AM	You would not want to spray to the underside of the slate, but it would not rot out the battens. As for the energy efficiency of unvented attics. They are far more energy efficient than installing foam or fiberglass to the floor of the attic space and venting the attic. Temperatures measured in the attic spaces in unvented configurations show temperatures in the attic within 7-8 degrees of the interior temperature even at severe outside temperatures without using more energy. This provides much greater efficiency, particularly if your duct work goes through your attic space. Note: It is true that a building code official may use or not use portions of the code at their discretion. But I have found most code officials do not like to stick their necks out unless they have first hand experience with the deviations from the code. So, if they are using the 2003 to the letter, they would have to be convinced the variance you are asking is credible. I have found that some will allow it but most will not.

Author

Comments

Timothy Johnson

Posted: Dec 26, 2007 06:45 PM

unvented attic

I am installing full envelope on new house in Brandon Ms. The inspector is using 2003 Int. Res.code book and it is not showing any allowance for unvented attic .I am using .5 lb foam.Can You email me a copy of a new code or codes that can help.City of Brandon has never had a foam insulated house and are requiring more info before allowing home to prceed

mason

Posted: Dec 29, 2007 09:33 PM

You can download the 2007 IECC Supplement at this link. http://www.iccsafe.org/cs/codes/2007-08cycle/2007Supplement/index.html

The section is 402 and 502 that discusses unvented attics.

Derek Martz

Posted: Mar 05, 2008 09:17 PM

Yes, Mason steered me onto a section in code that has a supplement added in 2007, which no allows for unconditioned attic, however my inspector told me that Pa does not acknowledge supplements, there fore I was required to add a supply and return in my attic. It meets code but will be removed as soon as I have occupancy, and besides the supplement will be added in the next code revision. So if your state doesn't allow supplements, then put it in and take it out later or just close it. Remember, if your attic has an access hatch and accessible then you need to have a 15min ignition barrier over your foam. Basically, you cannot see any foam after house it finished. I went through all this in Pa because no homes in my area where foamed either, and the inspector was following the written code to a "T".I'm trying to find a intumescent coating to cover my foam, but becoming increasingly difficult, so i will have to use another form of ignition barrier.

mason

Posted: Mar 07, 2008 07:43 AM

Unvented attics were approved in the 2004 supplement and included in the 2006 ICC code books. They were modified in the 2007 supplement. So, if your area is using 2006 ICC code, then unvented attics are acceptable. If they use the 2003 code, they are not.

David Kang

Posted: Mar 11, 2008 05:59 PM

Ahhh....no mason, that's not quite correct. The code allows any code official to accepyt anything he deems "better" than the code requirement. The code is a minimum standard, not a set of rules. The inclusion of the Unvented Attic assembly in the 2006 IRC (arguably in the addendum) INFERS it is an improvement....logic dictates that it is a better system. The code official has the right to accept it if he is so inclined.

Darren Gomez

Posted: Mar 12, 2008 01:23 AM

Please correct me if I'm wrong. The supplement allows for closed cell 1.5-2.0 foam. Does it acknowledge open cell foam at all or did I read that wrong. Is open cell foam allowed based on ICC codes?

Posted: Mar 22, 2008 11:32 PM

Was told that using an unvented attic was counter productive because I would be heating the attic space and moving the thermal barrier to the roof line?? Also, that the foam on the under side of a slate roof with open batten. Seams would allow moisture to leech beneath slate shingles and dissipate through the open batten and would have no where to go essentially rotting the batten board.

mason

Posted: Mar 23, 2008 11:07 AM

You would not want to spray to the underside of the slate, but it would not rot out the battens.

As for the energy efficiency of unvented attics. They are far more energy efficient than installing foam or fiberglass to the floor of the attic space and venting the attic. Temperatures measured in the attic spaces in unvented configurations show temperatures in the attic within 7-8 degrees of the interior temperature even at severe outside temperatures without using more energy. This provides much greater efficiency, particularly if your duct work goes through your attic space.

Note: It is true that a building code official may use or not use portions of the code at their discretion. But I have found most code officials do not like to stick their necks out unless they have first hand experience with the deviations from the code. So, if they are using the 2003 to the letter, they would have to be convinced the variance you are asking is credible. I have found that some will allow it but most will not.

You need to login to reply to this topic. Please click here to login.