Until 2016, fossil fuels as primary energy are included in the top three most widely used. The process of combustion of fossil fuels causes the release of tremendous amounts of carbon to the atmosphere. In the atmosphere, carbon turns into carbon dioxide (CO2) or often called greenhouse gas. Greenhouse gas has a negative impact on the environment: direct effects like acid rains, and indirect effects like global warming. In Indonesia, the buildings used 37.8 percent of the total national energy consumption and are directly responsible for 37.8 percent of CO2 emission. This study aims to discuss the impact of reducing energy consumption used by the household on the risk of greenhouse gases. A computer simulation was used to calculate energy consumption in buildings. A conversion method from building energy consumption to the amount of CO2 emission was used to determine the level of reduction of greenhouse gas risk. Some parameters were evaluated, such as building’s material (e.g., roof, wall) and building geometry. It was found that the energy consumption savings were around 66.1 percent and operational CO2 savings were obtained 923 kg/year.