Effect of Thermal Capacity Differences on Energy Consumption in Heating and Cooling in Detached Houses

Abstract

The well-scheduled operation of heating and cooling in detached residential houses in Japan means both the thermal insulation performance and the thermal capacity of the house affect energy consumption. Many previous studies have shown energy consumption differences between houses with different thermal insulation performance. On the other hand, other studies have shown heat load differences between houses with different thermal capacities, although few have examined the energy consumption differences between such houses. Therefore, this research uses a simulation to show the impact on energy consumption of various thermal capacities. The house simulation focuses on a representative detached house used for the national energy saving model of TRNSYS. The air conditioner simulation uses the COP model, which is also used for the national energy saving model. The simulation is carried out for a year with 5 minutes intervals. The room temperature settings are 20 degrees Celsius for heating and 27 degrees Celsius for cooling. To evaluate the effect of thermal capacity differences on energy consumption, six thermal capacity patterns are considered. One is taken from standard building construction and the others are introduced from ISO13790. Based on the simulation results, it was found that the annual total energy consumption for heating and cooling decreases as the thermal capacity of the house increases. In case of “very heavy” thermal capacity, which has the highest thermal capacity, the annual energy consumption was reduced by 11% for cooling and by 15% for heating. These results show that a higher thermal capacity decreases energy consumption for heating and cooling even though their thermal insulation performance is same. To evaluate the effect of thermal capacity differences on energy consumption under various scenarios, six levels of thermal insulation performance are considered, taken from the Japanese energy saving law. Based on the simulation results, the annual total energy consumption for heating and cooling decreases as the thermal insulation performance increases. In addition, energy consumption decreases as thermal capacity increases under the same thermal insulation performance. For the standard construction, which has the lowest thermal capacity, the reduction rate from increasing the thermal capacity tends to be larger in case of higher thermal insulation performance.