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Rigid Foam Question

hurlbz

Registered User
Joined
Nov 15, 2020
Messages
2
Location
Nova Scotia
Hello, I'm trying to find an answer on the requirements for rigid foam to be used to block air flow underneath a knee wall in my home, currently there is no air blockage and cool air is running right from the soffits under the kneewall. Google tells me rigid foam is typically used for this but I find the codes hard to decipher whether the foam would be considered "exposed" and if this is ok due to fire regulations, it's not in a livable space so I think it's ok but find the codes confusing, difficult to find and hard to follow (I'm a home owner, not a contractor). If someone could answer my question I'd appreciate it, basically can I put rigid foam to block the air flow through the floor joists underneath the kneewall or do I have to cover it up after? Also, for extra insulation I was thinking about putting foam on the outside of the kneewall (on the attic side), would this have to be covered?

Thanks again.
 

Rick18071

Sawhorse
Joined
Nov 28, 2009
Messages
2,640
Location
Poconos/eastern PA
If there is an access opening to this area foam cannot be exposed per 2015 R316.5.3. If you use the foam that has the thin metal coating on it you do not need to cover it.
 

hurlbz

Registered User
Joined
Nov 15, 2020
Messages
2
Location
Nova Scotia
Thanks for the replies, it wouldn't be exposed in the walk in area since it's under a floor, does that make it not exposed? For the other side of the house there is no access door, so you'd have to remove a panel to see it, I would also consider that not exposed?

Thats for the insulation for the joists anyway, sounds like for covering the wall it would be considered exposed (at least on the side that has an access door), is that reasoning correct?
 

tmurray

Registered User
Joined
Jun 10, 2011
Messages
1,923
Location
NB, Canada
If the foam is in the attic you are fine. There is nothing in the National Building Code of Canada that would require it to be covered if it is in the attic (or crawlspace for that matter).
 
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