Thermal environment and energy performance of well-insulated and airtight houses in Tohoku district of Japan.

Newly constructed residential houses in Japan are better insulated and more airtight than their predecessors to increase energy conservation. Although reduced energy consumption was expected, the energy performance of these buildings has not yet been clarified. Therefore, the indoor thermal environment and energy consumption in 300 well-insulated and airtight houses newly constructed in the Tohoku District, the northern part of Honshu Island, were investigated by a questionnaire survey. The information provided by the homeowners included the floor area, level of thermal insulation, space heating equipment, occupants behavior in regard of heating and ventilation, utility bills, problems with the indoor environment. This paper firstly describes the characteristics ofindoor thermal environment in the investigated houses and energy consumption. Secondly, the relationship between kerosene consumption for space heating and the influencing factors on energy consumption is discussed by a multi-regression analysis method. Thirdly, the influence of these factors on the heating load is estimated using computer simulations. The energy consumption of well-insulated and airtight houses investigated consumed more kerosene than the ordinary existing houses, because ofincrease in heated floor area and heating hours. Computer simulation reveal that the well-insulated and airtight houses in the Tohoku District consume more energy for space heating than ordinary existing houses, in which only the living/dining room is heated. The results also show, that it would be possible to keep a comfortable indoor environment with less energy consumption than the ordinary existing houses, if the houses had an insulation comparable to R2000 houses in Canada.