Can polyiso and spray foam contact a dryer duct?
BuildingNewb
| Posted in General Questions on
In completing my rim joist insulation project, I’ve come to an area where metal dryer duct exits the house. Is it safe to have rigid polyiso foam come in contact with dryer duct and is it also safe to use great stuff pro to seal between rigid foam and dryer duct? Thanks so much!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Building Newb,
As far as I know, it's OK for polyiso or canned spray foam to come in contact with a dryer exhaust duct.
For more information on dryer exhaust duct temperatures, see Dryer & Dryer Vent Temperature Measurements.
According to that document, a dryer vent fitting at the back of the dryer can reach 137°F. Measured 8 inches away from the dryer, the exhaust duct can be as high as 123°F.
Thanks, this would be roughly 5ft from the dryer. Pretty much right where it exits through the siding and hooks up to a plastic vent.
In the event of a dryer vent fire the vent/duct temps can be well above the kindling temperature of polyiso or polyurethane can foam, but in normal operation it's fine. Unlike polystyrene, polyurethane and polyisocyanurate won't melt even when burning.
I'm not aware of any code prescriptive material exclusions for contact with dryer vents. Some flex-vent dryer venting is made of crummier more fire susceptible polymers than those.
Thanks so much!
Since the Great Stuff website even recommends using it to seal around dryer vents, it seems to be an approved use of the product (they do recommend using the pest barrier version when sealing an exterior wall penetration).
http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0977/0901b80380977db0.pdf?filepath=styrofoam/pdfs/noreg/179-16011.pdf&fromPage=GetDoc