Actual measurement and numerical simulation were conducted in crawl space of detached houses, and the following points were clarified.
1. A house with high insulation performance of the floor insulation will have a lower temperature in the crawl space and higher humidity than a house with low.
2. Low temperature and high humidity becomes more noticeable in a house where it is difficult for outside air to flow into center of crawl space.
3. Outside air humidity has the largest effect on humidity of crawl space, followed by ventilation volume>thickness of floor insulation>cooling set temperature of room on 1st floor.
