The role of behavior on variation in domestic space heating demand in similar dwellings: What does it mean for the payback period of re-insulation?

Reducing domestic space heating demand is vital for meeting climate targets. Despite mature technologies and subsidies, re-insulation of the existing housing stock remains slow. This research quantifies the impact of occupant behavior on space heating demand and its economic implications for re-insulation. Using the Trnsys model, the heat demand of the case apartment was calculated and verified using monitoring data. The behavior was simulated for a well- and poorly-insulated apartment, and the payback time (PBT) for energy efficiency investments was assessed under different behavioral scenarios. Results reveal that occupant behavior can cause heat demand variation differing a factor 4.8 between high- and low-impact behavioral scenarios for a fixed building type, size, and insulation level. Key factors include partial heating practices and preferred indoor temperatures. Adjusting indoor temperatures during holidays and work hours has a larger impact on poorly insulated apartments. PBT variations for upgrading from label B to A range between 12 and 56 years, with the longer PBT observed for more energy-conscious behavior. In poorly insulated apartments, PBT varies between 6 and 29 years for upgrades from F to B and 11–56 years for F to D. This study highlights two key policy implications: 1) Accounting for occupant behavior is essential to avoid overestimating the energy savings and financial benefits of re-insulation. 2) While re-insulation may be profitable for average households, it may not be for those with below-average heating demand. Alongside market failures, this behavioral variation helps explain the slow adoption of re-insulation measures.