戸建住宅のインベントリ分析における問題点と対策

抄録

Objective. The case study of LCA analysis of a detached wooden house from cradle to grave by Process Analysis Method was performed as the second LCA Project by NEDO (New Energy and Industrial Technology Development Organization). The inventory data of a two-by-four system house and of an aluminum sash were collected in detail. For this two-by-four house, several kinds of aluminum sashes with different size were used as windows or terraces. However we obtained only one inventory data set of the most common sash. It is necessary to estimate the CO₂ emission of an unknown different size sashes from the known inventory data of the most common sash. The degree of data coverage is very important because the degree of precision of the analysis depends on it. The effect of data coverage on the precision of inventory analysis was performed for an aluminum sash, heat insulating aluminum sash and detached wooden house. The 1^st objective is to estimate the CO₂ emission of an unknown different size sashes from the known inventory data of the most common sash. The 2^nd objective is to make clear the effect of data coverage on the precision of inventory analysis.

Results and Discussion. For the 1st objective, several estimation methods were studied and the method that uses the power function of the ratio of perimeter was found to be the most precise and a simple method. For the 2nd objective, in the case of both aluminum sashes, about 70 weight % of degree of data coverage was enough to obtain 90% of CO₂ emission. On the other hand, in the case of the house, 90% CO₂ emission was obtained by 97 weight % of data coverage. In the case of the house, if the data coverage were calculated by accumulating materials weight in descending order of CO₂ emission, then 90% of CO₂ emission would be attained by 90 weight % data coverage. It is important to collect inventory data with the help of the information about CO₂ emission factor of materials.

Conclusions. In the case of aluminum sash, the CO₂ emission by production of any sash was found to be able to estimate from the only one known sash by the method that uses the power function of the ratio of perimeter. For collecting inventory data effectively, it is important to collect them in consideration with weight and also CO₂ emission factor of materials.