The aims of that study were to find out how the thermal capacity, resistance, and the placement of insulation layers affect relative humidity in crawl spaces. The results show that there are two alternative ways to use ground covers in combination with air change to achieve acceptable conditions in crawl spaces.
Moisture conditions in highly insulated outdoor ventilated crawl spaces in cold climates
Energy and Buildings, 2003, Vol. 35, n° 2, pp 175-187, 14 Fig., 1 Tab., 19 Ref.