The high cost of improving thermal insulation performance in houses is one of the hindrances to the spread of the improvement in thermal insulation performance, and it takes a long time to recover these costs through reduction of heating and cooling costs alone. Under such circumstances, in recent years, it has been reported that improvement in thermal insulation performance reduces the likelihood of various diseases among people inhabiting these houses, and this reduces medical costs. However, the relationship between thermal insulation performance and medical costs has not been quantitatively evaluated. If medical costs in relation to the thermal insulation performance of a house can be evaluated quantitatively, they can be taken into consideration in the recovery period of the costs of the improvement of the thermal insulation performance. Furthermore, it is possible to examine the most economical thermal insulation performance when considering the costs for thermal insulation, heating and cooling costs, and medical costs together.
Therefore, in this study, we estimated the medical costs in relation to the thermal insulation performance of the house, and examined the thermal insulation performance that is most economical when the costs for thermal insulation, heating and cooling costs, and medical costs are considered. Furthermore, we examined the cost recovery period for the improvement in the thermal insulation performance from that which satisfied the 2013 standard to the above-mentioned most economical thermal insulation performance, taking into consideration the reduction in heating and cooling costs and medical costs.
We assumed that the onset of various diseases is not directly affected by the thermal insulation performance of the house, but is affected by the thermal environment in the house, which is formed according to the thermal insulation performance of the house and the heating and cooling method. On the basis of the relationships between insulation levels of various houses and improvement rates in various diseases shown in the previous research, we estimated the thermal environments in houses in correspondence to each level of insulation and estimated medical costs from improvement rates in various diseases. We proposed formulas to estimate the medical costs for heart diseases and vascular brain diseases from the mean daily minimum operative temperature of the house from February 1 to February 7 and formulas to estimate the medical costs for diseases, excluding heart diseases and vascular brain diseases, from the mean operative temperature of the rooms the family inhabits from January 1 to February 28. We proposed these formulas separately for the age groups 0 to 19, 20 to 39, 40 to 59, and 60 and older.
Furthermore, using these formulas, we examined the most economical insulation performance, including insulation costs, heating and cooling costs, and medical costs. The average heat transmission coefficient of the envelope (UA value) of a house having this most economical insulation performance is 0.4 to 0.5 W/m2K for a floor-insulation house, and 0.36 to 0.4 W/m2K for a foundation-insulation house. We found that by considering not only heating and cooling costs but also medical costs, the cost recovery period for the improvement in the thermal insulation performance from that which satisfied the 2013 standard to the above-mentioned most economical thermal insulation performance was significantly shortened, to around ten years.
