We analyzed the difference in weight between construction materials that we measured and those calculated from blueprints for four different houses. Next, we determined the coefficient used to calculate CO 2 emissions based on the calculation using the actual measurements and those measurements taken from the blueprints. The following results were obtained.1) The weights of the construction materials used in the bases, the building frames and the roofs that were calculated from blueprints were both heavier and lighter than the actual measured values. The weights of the materials used in the outside walls that were calculated from blueprints tended to be lighter than the actual measured values.2) Our calculated coefficients are 98.5%�102.5% for the bases, 97.7%�105.9% for the building frames, 102.7%�116.3% for the roofs and 126.1%� 137.7% for the outside walls.