Analysis on design data of low energy housing in Japan

Abstract

Purpose / Context – In order to achieve low energy housing, it is important to quantitatively and comprehensively determine the effectiveness of energy saving technologies and to evaluate the energy conservation performance of an entire house. Low Energy Housing with Validated Effectiveness (LEHVE) is one of the measures for home energy saving in Japan. The evaluation procedure of LEHVE can quantitatively show the energy saving effect of each technology, such as insulation and equipment, and total energy consumption of a house in the design phase. The LEHVE’s evaluation procedure is not mandatory, however it is widely used in Japan and its outcome has developed into Japan’s Energy Saving Standard. Methodology / Approach – Design data of newly-built houses are investigated using the LEHVE’s evaluation procedure to evaluate the energy conservation performance in both mild climate region and hot humid climate region in Shikoku island, Japan. The present situation of energy conservation performance of newly built housing is analysed using the obtained data of the both regions. In the analysis, energy consumption, energy reduction rates and adoption rates of elemental technologies, such as natural energy application technology, heat control technology of building envelopes and energy-efficient equipment technology, have been yielded. Results – 370 cases of design data of newly built timber houses in Japan, which were obtained between FY 2013 and FY 2015, have been analysed based on the LEHVE’s evaluation procedure. 265 cases of design data were obtained in mild climate region and 105 cases were obtained in hot humid climate region. As the analysis results, it is suggested that the energy conservation performance of the newly built houses has been improved year by year in the both regions. Key Findings / Implications – The energy conservation performance of the newly built houses in both mild climate region and hot humid climate region has been improved year by year. However, some natural energy application technologies, such as wind utilisation or daylight utilisation, have not been widely adopted in the houses even though the both regions have suitable climates for use of natural energy. Originality – Energy conservation performance of housing can be estimated by using the LEHVE’s evaluation procedure. 370 cases of the latest design data of newly built housing have been obtained in Shikoku island where only dozens of data had been available by previous studies.