For clarification of discrepancy in LCA results caused by mismatches in the system boundaries of materials actually used and those of background data;
1) Matching ratios of the boundaries of materials in the manufacturing stage were calculated, with CO2-emission results ranging 40% to 80%.
2) Methods for developing database on errors were discussed, upon which an error database was created.
3) Using the database, errors found in 7 houses were analyzed and resulted in the variation coefficients ranging 0.15 to 0.30. This suggests LCA data on houses be carefully used for evaluation when small emission differences need to be interpreted.