Residential gas boilers for heating and hot water are major sources of greenhouse gas emissions. Hence, this study examines the environmental impact of greenhouse gas emissions from the combustion of fossil fuels in gas boilers used for domestic hot water and building heating. It investigates current residential heating practices to ensure adequate ventilation, maintain a healthy environment, and reduce odors. The article proposes a ventilation and heating scheduling protocol to minimize heat loss from air exchange between the building’s interior and exterior. This approach reduces the additional energy required to maintain thermal comfort inside the home. As a result, greenhouse gas emissions decreased, and air quality and environmental impact improved. The proposed protocol reduces fossil-fuel use and energy consumption by up to 20% and decreases annual greenhouse gas emissions per person by 252.7 kg. The study assumes that the boiler supplies hot water at a temperature higher than that required for standard domestic use, requiring mixing of hot and cold water at the tap. Regarding building heating, the research assumes a standard range of ventilation rates. The study concludes that, extrapolating the results of this work to a community of one million people, the reduction in carbon dioxide emissions could reach up to 257,000 metric tons per year. The analysis extends this recommendation to other domestic hot water and building heating systems, such as biomass boilers. The proposed method is more sustainable because it requires less fossil fuel and helps reduce atmospheric pollution.