Exposed Styrofoam insulation

Good evening all,

If foam boards are exposed within the building envelope (cold cellar, garage etc.) we consider this a fire safety hazard and recommend removal or drywall covering. What if the same Styrofoam is exposed in a heated crawlspace?

How about 2 stage foam covering it instead of 5/8 drywall?

Any help or comments are appreciated.

Keep safe,

Mark Ellison

First off - the crawlspace is (generally) not considered a living space. I agree that it should be covered in other “habitable” areas.

This may also depend on the AHJ - authority having jurisdiction. Is this a new house or older existing home?

Bottom line - unless the furnace is in the crawlspace - it likely poses very little hazard as fire safety concern.

Thanks Claude,

I agree that the threat is minimal, older home with an addition BTW. I’m more curious than anything, as to what the building code (did I say that out loud?) might say.



** Protection of Foamed Plastics **
Except as provided in Sentence (2), foamed plastics that form part of a wall or ceiling assembly in *combustible construction *shall be protected from adjacent space in the building other than adjacent concealed spaces within attic or roof spaces, crawl spaces, and wall assemblies, by,
(a) one of the finishes described in Subsections 9.29.4. to 9.29.9.,
(b) sheet metal mechanically fastened to the supporting assembly independent of the insulation and having a thickness of not less than 0.38 mm and a melting point not below 650°C provided the building does not contain a Group C major occupancy, or
© any thermal barrier that meets the requirements of Clause Heated and Unheated Crawl Spaces
Crawl spaces shall be considered to be heated where the space,
(a) is used as a hot air plenum,
(b) contains heating ducts or heating pipes that are not sealed and insulated to minimize heat loss to the space, or
© is not separated from heated space in accordance with Section 9.25.
Heating of heated crawl spaces shall conform to Section 9.33.

Insulation, an *air barrier system *and a *vapour barrier *shall be installed in the walls of heated crawl spaces in accordance with Section 9.25.:slight_smile:

I think it says we don’t need fire protection, but we need a vapour barrier over the foamboard in the crawlspace, but who’s doing that?

John Kogel

Alot of foam products have a vapour permeance of less than 0.99 therefore they act as a vapour/air barrier as well.

Thanks Claude, much appreciated.