Fibreglass batt insulation in crawlspace floor joists is the most common insulation failure Western Insulation finds in older Langley homes — and it fails specifically because of BC's damp climate. Fibreglass absorbs moisture from damp crawlspace air and holds it directly against structural floor joists, creating the conditions for mold and structural damage that progress for years before any visible sign appears inside the home. Closed-cell spray foam on crawlspace walls does not absorb moisture, does not support mold growth, and acts as both insulation and vapour barrier simultaneously. Full guide at westerninsulation.ca/basement-and-crawlspace-insulation/