BC Building Code requires a vapour barrier in every crawlspace — and a 10 to 20 mil polyethylene liner is the standard for Langley BC installations. Without it, ground moisture evaporates upward from the soil into the crawlspace air continuously, condensing on every cold surface it contacts and creating the persistent moisture conditions that drive mold growth in floor joists and subfloor panels. Western Insulation installs code-compliant vapour barriers as a standard component of every Langley crawlspace insulation project — never an optional add-on. Book at westerninsulation.ca/basement-and-crawlspace-insulation/