Abstract
The properties of building envelopes significantly affect indoor building energy consumption, indoor thermal comfort, and building durability. In the current standards for Japanese residential energy efficiency, insulation placement is not well regulated. Meanwhile, it is common in Japan to use air-conditioning intermittently, rather than having the units operate continuously. Therefore, considering specific Japanese lifestyles, we investigated insulation performance. In this research, we: (1) developed the interior insulation to include insulation on walls, ceilings and floors of building units (all of the interior surfaces) to achieve building energy savings by avoiding heat loss through thermal bridges; (2) discussed and demonstrated the effects of high heat capacitance for each of the building components and the thermal bridge by conducting building environmental simulations; (3) conducted simulations in seven cities in Japan and discussed the applicability of these different weather conditions; and (4) compared temperature distributions to investigate differences in indoor comfort with partial heating on winter nights. We demonstrated the energy saving and thermal comfort advantages of interior insulation. This research provides an innovative insulation style based on Japanese lifestyles that contributes to new energy-saving standards and formulations.
Highlights
In 1999, the Japanese Institute for Building Environment and Energy Conservation established the residential energy efficiency standard to specify the performance of building envelopes and overall thermal loss
Due to the optimization achieved in regard to this thermal bridge, the heat loss in the interior insulation unit was around 40% lower than the loss in the existing outside and inside insulation units
In an interior insulation unit, the peak time of the interior surface temperature was the same as the outdoor air temperature, and the temperate difference between the interior wall surface and the indoor air temperature was very slight when the AC was turned on. This is to say, a lower heat capacity of the building envelope contributed to greater control of indoor thermal conditions and reduced the cooling load on summer days
Summary
The “Act of the Rational Use of Energy” (May 2008) and the “Energy-Saving Standards for Houses and Buildings” (January 2009) were enacted [1] These acts, were not proposed for improving energy saving levels at residential units. It is necessary to clarify the properties of various insulation styles in apartment units and the mechanism of effects from insulation on thermal comfort and energy use [2]. It shows that building envelopes with high insulation properties should be introduced to the building exterior walls, floor slabs and the other components of the building envelope [3]. This guideline does not indicate details about the differences between insulation styles with an environmental variation and does not mention the effects of thermal bridges
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