This study summarizes measured data on energy savings from conservation retrofits in existing residential buildings. Retrofits to the building shell, principally insulation of exterior surfaces, window treatments, and infiltration-reduction measures, are the most popular, although data on various heating system retrofits are now available. The average retrofit investment per unit in multifamily buildings is approximately $700, far lower than the average of $1350 spent in single-family residences. Savings achieved are typically 20% to 30% of pre-retrofit space heating energy use, although large variations are observed both in energy-savings and in costs per unit of energy saved. Particularly cost-effective retrofit strategies are identified based on measured energy use data . Predicted versus actual savings are also compared for groups of homes in 24 retrofit projects.

Units: Dual