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

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Kris Russell Posted: Sep 13, 2011 10:20 PM	ignition barrier in attic When you spray the roof deck and the ac unit is in the attic do you need to spray the entire area of the roof deck with an ignition barrier or just the immediate area?
mason Posted: Sep 15, 2011 07:51 AM	Yes you do need to cover all of the foam. Also, be sure that the attic is not the plenum for the AC unit and that it has its own outside air source. If the attic is supplying the air for the AC, then it becomes a plenum and you can only use a foam that has a less than 25 flame spread and less than 50 smoke developed rating. Most of our sprayfoams can achieve the flame spread rating but not the 50 smoke rating. The best way to determine if you need an ignition barrier is to obtain a copy of the supplier's ICC evaluation report (or NPFA evaluation report if covered by the NFPA code). You can look up the supplier's evaluation report at www.icc-es.org/Evaluation_Reports/index.shtml The report will tell you where and when a sprayfoam can be installed with or without an igntion barrier and with what materials would qualify as an ignition barrier for that foam. Note a few foams do not require ignition barriers in attics based on passing specific fire tests as outlined in the sprayfoam acceptance criteria AC 377.
mason Posted: Sep 27, 2011 08:14 AM	I would like to correct my previous reply. The codes have changed since I last reviewed them concerning plenums. According the 2009 and the 2006 IBC code books, you can use a foam that has a 25 flame spread and 450 smoke rating in plenums so long as the foam is covered by a code approved thermal barrier. The same applies to the IRC, except for plenums under floors. The foam is required to have 25 flame spread and 200 maximum smoke rating. Thanks to Roger Morrison for bringing this to my attention. The 25/50 rule still applies to insulation in ducts in attics with one exception. The codes allow a sprayfoam on duct work that has a 25 flame spread and 450 smoke developed rating in residential applications, but not that exception is not listed in the 2009 IBC.

Author

Comments

Kris Russell

Posted: Sep 13, 2011 10:20 PM

ignition barrier in attic

When you spray the roof deck and the ac unit is in the attic do you need to spray the entire area of the roof deck with an ignition barrier or just the immediate area?

mason

Posted: Sep 15, 2011 07:51 AM

Yes you do need to cover all of the foam. Also, be sure that the attic is not the plenum for the AC unit and that it has its own outside air source. If the attic is supplying the air for the AC, then it becomes a plenum and you can only use a foam that has a less than 25 flame spread and less than 50 smoke developed rating. Most of our sprayfoams can achieve the flame spread rating but not the 50 smoke rating.

The best way to determine if you need an ignition barrier is to obtain a copy of the supplier's ICC evaluation report (or NPFA evaluation report if covered by the NFPA code).

You can look up the supplier's evaluation report at

www.icc-es.org/Evaluation_Reports/index.shtml

The report will tell you where and when a sprayfoam can be installed with or without an igntion barrier and with what materials would qualify as an ignition barrier for that foam.

Note a few foams do not require ignition barriers in attics based on passing specific fire tests as outlined in the sprayfoam acceptance criteria AC 377.

mason

Posted: Sep 27, 2011 08:14 AM

I would like to correct my previous reply. The codes have changed since I last reviewed them concerning plenums.

According the 2009 and the 2006 IBC code books, you can use a foam that has a 25 flame spread and 450 smoke rating in plenums so long as the foam is covered by a code approved thermal barrier.

The same applies to the IRC, except for plenums under floors. The foam is required to have 25 flame spread and 200 maximum smoke rating.

Thanks to Roger Morrison for bringing this to my attention.

The 25/50 rule still applies to insulation in ducts in attics with one exception. The codes allow a sprayfoam on duct work that has a 25 flame spread and 450 smoke developed rating in residential applications, but not that exception is not listed in the 2009 IBC.

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