Foam application on ductwork?

[Rick Hurst]

Should spray on foam insulation be on ducts? I've never seen this before.

Thanks,
Rick

[Raymond Wand]

Found this article from the the forum at the link below.

Foam on ducts on Spray Foam Q&A Forums Message Boards - SprayFoam.com (http://sprayfoam.com/mnps/fullthread.cfm?threadid=11346&mnboardid=5&mnforumid=2&startat=1)

There is a conflict in the ICC codes. The IRC (residential code) specifically allows the use of SPF on ducts in attics and crawlspaces. However, the IMC (mechanical code) does not allow any insulation that does not have a 25 flame spread or less and a less than 50 smoke rating.

Show them the section in the IRC that allows SPF (with a suitable ignition barrier) stressing that this is a residential construction and should go by the IRC and not the IMC (which is for commercial buildings primarily).

The section is M1601.3 in Chapter 16 of the IRC

"Duct coverings and linings, including adhesives where used shall have a flame spread index not higher than 25 and a smoke developed index not more than 50...

Exception: Spray application of polyurethane foam to the exterior of ducts in attics and crawl spaces shall be permitted subject to all of the following:

1. The flame spread index is not greater than 25 and the smoke developed index is not greater than 450 at the installed thickness.

2. The foam plastic is protected in accordance with the ignition barrier requirements of Sections R316.5.3 and R 316.5.4

3. The foam plastic complies with the requirements of Section 316." (the foam plastics section of the IRC)

[Scott Patterson]

I have seen it before, and I could not find anything that said it was wrong when I researched it several years ago.

[ted kidd]

You are likely to be seeing more and more of this in high performance homes. Kills three problems in one pass; duct leakage, condensation/moisture within porous insulation, and dramatically increased effective r value.