The environmental impact of the zero energy ready home program on manufactured housing

Manufactured homes, which are built in the factory and shipped to the site, provide economical housing for more than 20 million Americans. To improve energy measures and facilitate deployment of renewable energy systems to achieve net zero energy in manufactured homes, the U.S. Department of Energy (DOE) made public the Zero Energy Ready Home (ZERH) National Program Requirements for manufactured housing in 2022. To understand how these changes will impact the environment and the building's durability, life cycle assessment and hygrothermal simulations were carried out for a standard manufactured home design and two ZERH designs in Knoxville, Tennessee. The embodied carbon and operational emissions were compared for the standard design and two ZERH designs for a service life of 60 years. Operational emissions were determined using the Building Energy Optimization tool, BEopt, and durability assessment was carried out using WUFI Pro. Life cycle assessment was performed in accordance with ISO 14040 using Athena's Impact Estimator for buildings. Results indicate that the investment in embodied carbon of the zero energy ready homes is small relative to the savings in operational emissions. The increase in embodied carbon in the zero energy ready homes is offset by the reduction in operational emissions compared to the standard home for the first year of operation. With an investment of 59 kg CO₂ eq in embodied carbon, the reduction in operational emissions is approximately 680 kg CO₂ eq after one year compared to a construction that meets the prescriptive performance of the building code for manufactured housing.