Introduction:
Considering the relationship between the environmental load and the environmental quality is very important in design of the ecological housing. Moreover, the importance of study from the viewpoint of lifecycle is increasing. This study aims to clarify relations between LCCO2 and thermal environment in passive solar house with thermal mass.
Method:
Firstly, the settings for the model of living room with various combinations of window and thermal mass are assumed. The models are mainly based on wooden structure with the wide frontage facing south to gain solar heat. The supposed site is in suburb area of Tokyo, Japan. Three variations of the south window are set by size and position of opening and depth of eaves. Besides, four compositional variations of thermal mass to store solar heat are set by position and amount of reinforced concrete element. Consequently, the twelve models are set for following investigations. Secondly, the amount of embodied CO2 for each model is calculated by LCA tool offered by the Architectural Institute of Japan. Thirdly, the amount of operating CO2 emitted from the air-conditioning load is calculated by the Solar Designer which is a thermal environment simulation tool. Furthermore, the qualities of thermal environment focusing on the change of room temperature on sunny day in winter and summer are investigated by considering the Degree・Hour (D・H) which integrates the fluctuation of room temperature. Finally, the amount of LCCO2 is calculated by combining the embodied and operating CO2, and then, the relationships between LCCO2 and thermal environment quality by D・H are clarified.
Results:
1) The model AS which has the smallest thermal mass and window indicates the smallest embodied CO2. On the other hand, the model CL which has the second largest thermal mass and the largest window shows the largest embodied CO2. These are regarded by differences for the repairing cycle of element.
2) The models of A, B and C which have larger thermal mass tend to indicate smaller operating CO2 according to reduction of window size. However, only the model D with the largest thermal mass shows a different tendency that indicates smallest operating CO2 in the case with medium window size.
3) The room temperature’s change tends to become smaller along with increase of thermal mass. However, the model DS which has largest thermal mass and smallest window shows minimum D・H in winter which is a stable environment in low temperature.
4) For the relations between LCCO2 and thermal environment, the models AS, BM, CM and DL which have different combinations of thermal mass and window size indicate smaller LCCO2 with an appropriate D・H combination in winter and summer. Especially, the model AS and DL have contrastive difference for the passive design strategy regarding with the less or more thermal mass and the smaller or larger window for solar gain, in addition to their differences for the combination of embodied CO2 and operating CO2. This result means a “trade-off” relations between LCCO2 and thermal environment and shows alternatives for design regarding the balance of thermal mass and window with proper combination of environmental load and quality.
