Outlines three surveys relating to moisture in house crawl spaces in a cool temperate climate and conclusions drawn from them. The surveys were - (1) A two-year survey of ten houses, monitoring moisture conditions in crawl spaces and roof spaces where the two were coupled by air leakage paths. Three different remedial treatments were tested, including covering the ground with polyethylene film. This ground cover was assessed later as at least 70% and possibly up to 95% effective. (2) A pilot study on measurement of subfloor ground evaporation using lysimeters, leading to a one-year survey on ground evaporation under 60 houses in three towns. Average evaporation was on approximately 400 g/(m²×day). (3) A small survey on subfloor natural ventilation rates and the interchange between the subfloor and other parts of the building. This survey showed that a NIST model correlated well with observed air exchange.

KEYWORDS: crawl spaces, ventilation, moisture, New Zealand, roof spaces, foundations, moisture barriers, measuring, housing.