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Posted: Nov 10, 2007 04:46 PM
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Foam over ducts
I am getting mixed results about spraying my ducts w foam, I have a ranch house and my ductwork is in the attic, and I do have a small access. I want to get the best out of my system, so I would like to foam them. Can I spray any foam over my metal ductwork, and if so, what type and then do I have to cover it with a particular product? (ignition or thermal barrier) I'm told it must have fire and smoke classifications, however, all foam meets E-84 requirements. I.m foaming all my exterior walls and have a vented attic, any suggestions. My unit is in basement, and only ducts in attic, very small not useable space.((only crawl around attic.
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mason
Posted: Nov 10, 2007 08:10 PM
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The IRC 2007 supplement allows the use of closed cell foam on ducts in attics. It must be covered with an ignition barrier. |
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Posted: Nov 10, 2007 09:09 PM
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what is classified as ignition barrier, drywall fiberglass wrap etc... because i have metal ducts and wondering how to cover it. and thanx for responding. |
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mason
Posted: Nov 11, 2007 07:58 PM
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The ICC codes list the following as ignition barriers; 1 & 1/2 inches of mineral fiber (fiberglass or rockwool), 1/4 inch of wood paneling, plywood etc, .016 thick metal, drywall, Intumescent coatings are not listed in the codes as ignition barriers, but if tested and pass the SWRI fire test may be listed with specific foams in specific applications. The foam manufacturer would have an ICC Evaluation Report listing the foam and the coating and how it can be used in the attic or crawl space. |
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Tim O'Keefe
Posted: Nov 11, 2007 09:46 PM
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I find it funny that they allow wood as an ignition barrier. Once the wood ignites doesn't that pose an even larger ignition source to what is underneath and supposed to be protected?? Tim Granite State Spray Foam Co. |
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Posted: Nov 11, 2007 11:13 PM
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Thank you for all u knowledge and help I will Pass it on to my code official. Also, I believe I can use a fiberglass wrap on ducts after I foam them to meet the ignition barrier, THANX AGAIN!!!! |
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mason
Posted: Nov 12, 2007 08:03 AM
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When tested in room corner fire tests, the wood burns differently than foam plastics. Foam plastics such as polyurethane can flash at a fairly low temperature then forms an intumescent char on the surface. But the speed and the amount of smoke that is developed from the flash fire makes foam a fire hazard. The ignition barrier prevents the flash from occuring. That is why wood can be used as an ignition barrier, it prevents the flash from occuring until after the wood burns away. This would give someone in the attic time to get out of the attic before the flash occurs. Please read SPFA's technical document AY 126, Thermal and Ignition Barriers. It can be downloaded at sprayfoam.org for no charge. |
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Posted: Nov 13, 2007 05:08 PM
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As you stated in p=previous discussions, It is probally better to leave ducts uncovered in unvented attic space, wont my inspector have a problem with that? And One last question, if I have 3inches cc in 2x8 wall, which is better for efficiency adding batts to fill space, or to leave air gap, I am only trying to have the best I can without wasting money, I would use cellulose but don't want to spend the extra money, I have tons of r-30. |
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Posted: Nov 13, 2007 05:08 PM
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mason
Posted: Nov 13, 2007 05:14 PM
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The sprayfoam will allow the fiberglass insulation to perform better, so it will provide some additional energy efficiency, but maybe not enough to justify the added expense. |
