This paper reviews empirical data from evaluations of the influence of residential energy efficiency retrofits on indoor environmental quality conditions and self-reported thermal comfort and health. Data were extracted from 36 studies described in 44 papers plus two reports. Nearly all reviewed studies were performed in Europe or United States. Most studies evaluated retrofits of homes with low-income occupants. Indoor radon and formaldehyde concentrations tended to increase after retrofits that did not add whole-house mechanical ventilation.

Cost savings from efficiency gains are at the core of the green building business case. Significantly lower energy bills are said to be a major factor in the green rent premium observed in earlier studies. Our study tests this relationship by inferring energy costs from operating expenses for a large dataset of U.S. office buildings and relating them to rental rates. We find that eco-certification is associated with a higher than anticipated total energy expenditure, which is the opposite of its expected effect.

Heat pumps are relatively simple appliances. They share similar components to refrigerators and air conditioners and effectively move an external source of heat to where it is needed, such as in buildings for heating or the production of hot water. Their key value is efficiency; for each unit of electricity consumed to operate them, they produce multiple units of usable heat. Because of this, they require much less energy input for a similar heating outcome compared to combustion technologies, making them naturally cleaner and generally cost effective to run.