Proposal for optimum combination of reflectivity and insulation thickness of building exterior walls for annual thermal load in Japan

This paper is a proposal to optimize the combination of surface reflectivity and the insulation thickness of exterior walls for energy savings in regions of Japan. Calculations of building thermal loads and economic analysis of the total cost for six cities from high-latitude to low-latitude regions of Japan were carried out for a range of surface reflectivity and insulation thickness of exterior walls. The results can be used in design to decrease the energy requirements of buildings. We estimated the annual thermal loads of a simulated building floor and analyzed the cost of the building envelope in Sapporo, Tokyo, Nagoya, Osaka, Fukuoka and Naha, Japan, varying the surface reflectivity of the exterior walls from 0.1 to 0.8, and insulation thickness of the exterior walls from 10 mm to 100 mm, using the thermal load calculation software, New HASP/ACLD-beta and cost analysis. Optimum combinations of surface reflectivity and insulation thickness for each region are proposed. (C) 2016 Elsevier Ltd. All rights reserved.