Heat and insulation capacities were evaluated by a regression analysis between the indoor-outdoor difference of temperature and the coefficient of variation of indoor temperature coupled with the way of living. Airtightness and ventilation were evaluated by a regression analysis between the indoor-outdoor difference of temperature and that of absolute humidity. The thermal performance in 5 houses with patients of atopic dermatitis was compared using the procedures described above. Absolute and relative humilities were extremely low in one patient house that had high-frequency ventilation.