This study compared the performance of closed crawlspaces, which had sealed foundation wall vents, a sealed polyethylene film liner, and 1.0 ft3/min (0.5 L/s) of HVAC supply air for each 30 ft² (2.8 m²) of crawlspace ground surface, to traditional vented crawlspaces with wall vents and polyethylene film covering 100% of the ground surface. The study was conducted at 12 owneroccupied, all-electric, single-family detached houses with the same floor plan located on one cul-de-sac in the southeastern United States. Using the matched pairs approach, the houses were divided into three study groups of four houses each. Comparative moisture measurements for these crawlspaces and submetered heat pump kWh use were recorded. Findings supported that for the humid conditions of the southeastern United States, properly closed crawlspaces were a robust measure that prodproduced substantially drier crawlspaces and significantly reduced occupied space conditioning energy use on an annual basis