Use only medium density spray polyurethane foam meeting the requirements of CAN/ULC S705.1 Material Standard. DO NOT AT ANY TIME use “open cell” or “1/2 pound” foam in a crawl space where it may be in contact with moisture. The clauses in the National Building Code which apply to medium density spray polyurethane foam insulation are:
220.127.116.11 Protection of Foamed Plastics
18.104.22.168. Protection of Foamed Plastics
1) Except as provided in Sentence (2), foamed plastics which form part of a wall or ceiling assembly in combustible construction shall be protected from adjacent spaces in the building , other than adjacent concealed spaces with attic or roof spaces , crawl spaces* , and wall assemblies, by
a) one of the interior 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 0.38mm and a melting point not below 650°C, provided the building does not contain a Group C major occupancy , or
c) any thermal barrier that meets the requirements of Clause 22.214.171.124.(2)(e).
Crawl spaces are defined in the NBC in Clause
126.96.36.199. Crawl Spaces
1) Where a crawl space exceeds 1.8m in height or is used for any occupancy or as plenum in combustible construction or for the passage of flue pipes , it shall be considered as a basement in applying the requirements in Article 188.8.131.52.