The Environmental Impact of Deep Energy Retrofits in Residential Construction

Almost two thirds of the residential homes in the U.S. were constructed before the U.S. Department of Energy implemented energy conservation measures that were later formalized in the building codes. To reduce energy consumption and carbon emissions from the built environment, improvement to the existing housing stock is a prerequisite. However, improvements that lower energy consumption address carbon emissions related to heating, cooling and plug loads but not the embodied carbon of the building materials that also contribute to global carbon emissions. As the enclosure is made more efficient a larger portion of total carbon emissions is embodied carbon from the building materials. To mitigate carbon emissions, a holistic approach is required so that any improvement to the home results in a net reduction in carbon emissions. To understand the overall environmental impact of building enclosure improvements, the embodied and operational carbon emissions are calculated in this investigation and compared to the overall energy savings associated with enclosure improvements. The energy savings together with a reduction in operational carbon emissions are calculated using a novel building envelope metric. The net carbon emissions are then determined before and after the energy improvement measures. This approach allows or enables architects and builders to select designs that result in maximizing the overall reduction in energy and carbon emissions.