Energy (in)efficient comfort practices: How building retrofits influence energy behaviours in multi-apartment buildings

One of the main strategies employed to increase the energy efficiency of buildings is the insulation and sealing of building envelopes. This has led to considerable reductions in energy consumption in recent decades. However, with the increasing efficiency of the building envelope, a contrary effect is also evident: energy performance gaps (EPGs), the phenomenon where actual consumption exceeds calculated demand. While EPGs have often been associated with rebound effects, socio-technical studies argue that it is the interactions between occupants and buildings (or building technologies), which have negative, often unintended, consequences for energy consumption. To analyse these interactions and their contribution to EPGs, we conducted a survey of 34 households in two moderately insulated multi-apartment buildings and calculated EPGs at the apartment level. Based on the results, we argue that increasing the building insulation can lead to negative interaction effects because occupants adapt to the changes in building behaviour, producing a shift in energy consumption for the whole building. Building inertia and reduced feedback are likely accompanied by higher indoor temperatures and increased ventilation. We suggest that a better understanding of these mechanisms is necessary to evaluate the real savings of different efficiency measures, and discuss various implications for policy and research.