This paper focuses on how to reduce CO 2 emissions regarding construction materials. We compared section by section the amount of CO 2 emissions from the four different houses. Next, we made an improved plan that took away the first floor that was constructed with reinforced concrete, as well as the interior decorations which emitted less CO 2 during their factory production. The following results were obtained. 1) We determined which sections of the four houses had less construction waste. We determined which sections of the four houses emitted less CO 2 during their production. 2) The total amount of CO 2 emissions per floor from construction materials is 318.8kg-CO 2 /m 2 �498.1kg-CO 2 /m 2. 3) The proposed countermeasure that took away the first floor reduced CO 2 emissions by 15.7×10 3 kg-CO 2 , a decrease of 30.4%.The proposed countermeasure that used the interior decorations, which emitted less CO 2 during their factory production, reduced CO 2 emissions by 5.1×10 3 kg-CO 2 , a decrease of 9.9%.The countermeasure that the authors described in their improved plan reduced CO 2 emissions by 20.8×10 3 kg-CO 2 , a decrease of 40.3%.