Estimation of the relationship between the thermal environment of a house in winter and its occupants' health

Abstract

This study aims to quantify the relationship between the arbitrary thermal environment of houses in winter and their occupants' health through a comprehensive questionnaire survey, involving approximately 24,000 individuals who moved into insulated dwellings in Japan. A relationship between the degree of the thermal insulation of these houses and corresponding rates of improvement in the following 10 diseases were formulated: heart disease, cerebrovascular disease, hypertension, diabetes mellitus, asthma, dermatitis and eczema, pneumonia, inflammatory polyarthropathies, allergic rhinitis, and conjunctivitis. Following the statistical analysis of these outcomes, significant differences in improvement rates were identified among the levels of the thermal insulation of houses for the following five diseases: cerebrovascular diseases, asthma, dermatitis and eczema, allergic rhinitis, and conjunctivitis. In addition, the thermal environments of houses corresponding to each thermal insulation level were estimated by numerical simulations. Using these results, we organized the relationships between the thermal environment conditions of houses and observed prevalence rate for the following four diseases for which the improvement rates increased with increasing insulation levels and significant differences were identified: asthma, dermatitis and eczema, allergic rhinitis, and conjunctivitis. Consequently, we formulated equations to predict the prevalence rates of these diseases using the "mean operative temperature of rooms occupied by each family member from January 1 to February 28."