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.

Residential energy efficiency interventions are complex social and construction programmes that may benefit health, yet the interactions between the material improvements, health and health-related outcomes, and householder responses are not well understood. While indoor winter warmth and householder satisfaction have been identified as the key mediators for physiological, mental and social health outcomes, this paper explores how programme contexts may have influenced the outcomes. This review revealed that common target populations were low income households, children and the elderly.

This study presents three cost-optimal calculations. The overall aim is to provide a deeper analysis and to provide additional guidance on how to properly implement the cost-optimality methodology in Member States. Without proper guidance and lessons from exemplary case studies using realistic input data (reflecting the likely future development), there is a risk that the cost-optimal methodology may be implemented at suboptimal levels.