Monthly gas and electricity use data from a set of 13 study apartments and 20 control apartments from three apartment buildings (B1 -B3) in California were analyzed. The study apartments were retrofit with simultaneous energy savings and indoor environmental quality (IEQ) improvements as the goal. The control apartments were not retrofit. Pre-retrofit modeling indicated annual energy savings of 21%, 17%, and 27% for the study apartments in B1-B3, respectively. Based on a comparison of changes in energy use of study apartments to energy use changes of control apartments, total measured savings of gas energy plus site electrical energy were 28% in B1, 5% in B2, and 3% in B3. Given the small number of study apartments and the substantial changes in energy use within control apartments, the project yielded no conclusive evidence of energy savings. Apartment energy use increased with number of occupants and with floor area; however, the association with occupancy was most evident. Climate differences did not appear to be the major driver for the variability in energy use among apartments. Changes in occupant behaviors affecting energy use may have overwhelmed and obscured the energy savings in this small number of buildings. Much larger prior studies employing similar retrofits indicate that the retrofits usually do save energy. BACKGROUNDThe U.S. is implementing many energy retrofits in homes with the goal of reducing building energy consumption and carbon dioxide emissions, as well as improving national energy security. Several protocols and tools exist to help with the selection and implementation of housing energy retrofit measures [1]. These protocols are typically based on energy models, engineering judgment and costbenefit analysis, rarely considering potential effects on indoor environmental quality (IEQ). Features of IEQ that may be affected by retrofits include thermal comfort conditions, indoor air pollutant concentrations, and acoustic and lighting conditions [2][3][4]. Although retrofit efforts provide an opportunity to simultaneously save energy and improve occupant's health and comfort, potential IEQ improvement opportunities are often not considered during selection of retrofits measures.