Frontiers of weatherization: Evolving programmatic needs and expanding evaluation tools

Low-income weatherization programs provide home energy efficiency upgrades to reduce utility costs, improve indoor comfort, and address the health and safety needs of income-constrained households. This review examines seventeen retrospective, outcome-focused evaluations of weatherization programs conducted over the past four decades to assess how program evaluation methods have evolved, where critical gaps remain, and how future studies can improve. This review highlights key developments in evaluation design and causal inference methods, from early pre-post comparisons to recent use of randomized encouragement designs, matching techniques, and staggered difference-in-differences estimators. Second, it evaluates the potential of new digital and physical tools such as smart meters, sensors, and other measurement and verification technologies to improve data collection for more timely and precise evaluation. Third, it identifies growing programmatic needs that evaluations must address, including persistent barriers to participation and the expansion of weatherization services to homes requiring pre-weatherization repairs. Across prior studies, we find that many evaluations remain limited by small or unrepresentative samples, selection-biased control groups, and reliance on self-reported or inconsistent data. No evaluations to date have incorporated community-based participatory research (CBPR) approaches, limiting their responsiveness to local needs. The review concludes by offering recommendations for strengthening future evaluations, including strategies for incorporating CBPR, improving data access, and leveraging advanced econometric tools.