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Recently, insulation retrofits of existing houses have been thought to be one of the effective measures from the viewpoint of global warming prevention. However, the overall reduction effects of environmental loads by the insulation retrofits have not yet been clarified. This study intends to accumulate basic data concerning the insulation retrofits and to promote the energy saving of existing houses.
The environmental performances of 4 detached wooden houses in Tohoku region, Japan before and after the insulation retrofits were investigated. The indoor thermal environments, energy consumption, and performances of insulation and air tightness before and after the retrofit were analyzed. In addition, the effects of insulation retrofits were clarified.
The heat loss coefficient (“Q”) and the equivalent air leakage area in proportion to the floor area (“C”) were calculated in each house before and after the retrofit. After the retrofit, the values were changed to Q=1.2 W/m2K & C=2.1 cm2/m2 in house_A and Q= 1.5W/m2K & C=1.1 cm2/m2 in house_B.
During winter, in house_C, temperature differences between the living room and other rooms went up to 20 ℃ before the retrofit. After the retrofit, temperature differences were limited about 5 ℃, and the indoor vertical temperature difference was 2.5 ℃at a maximum.
In house_A, city gas was used twice and once a day before and after the retrofit respectively. The average values of city-gas consumption were 10 kW and 8 kW before and after the retrofit respectively.
Comparing annual energy consumption before and after the retrofit, in houses_A and B, energy consumption were decreased by 35% and 44% after the retrofit respectively. However, in house_D, energy consumption was increased by 42% because the insulation retrofit had partial effect.