Disentangling rebound effects and construction errors in building retrofits using integrated energy signature analysis

Building retrofits have become a vital strategy for achieving carbon neutrality in the building sector, yet numerous cases report that the anticipated energy savings after retrofit interventions are not fully realized. The observed performance gap can be attributed to factors such as reduced energy saving effects due to occupant usage characteristics, rebound effects, and errors occurring during the design phase.

To investigate the underlying reasons for these lower-than-expected energy savings, this study proposes an Integrated Energy Signature (IES) analysis method that utilizes publicly available data. The proposed methodology employs a data-driven approach using a Change Point Model (CPM) to analyze the energy consumption associated with heating and cooling. Initially, a CPM-based algorithm was applied to derive key parameters for each building, including base load, heating and cooling slopes, and heating and cooling change points.

Subsequently, the differences in these parameters before and after retrofit interventions were calculated to generate energy signatures that represent changes in energy consumption patterns. Based on these results, the study presents an IES analysis method that integrates the energy signatures derived from public data. The resulting IES reflects a composite signature that incorporates both the building’s thermal performance and occupant behavioral factors, thereby enabling a more precise assessment of the actual performance changes following retrofit.

Application of the proposed methodology allowed the classification of post-retrofit performance degradation factors into three distinct categories. First, the critical temperature rebound effect describes the phenomenon in which occupants adjust their heating and cooling setpoints, thereby offsetting the expected energy savings. Second, the base load rebound effect is characterized by an increase or sustained energy consumption irrespective of outdoor temperature due to the installation of additional equipment. Third, construction errors refer to situations where the intended improvements to the building envelope are not achieved, resulting in a deterioration of thermal performance.

The proposed IES method provides a robust framework for evaluating performance shortfalls that conventional simulation methods struggle to assess. It underscores the need to combine technical performance data with occupant behavior to enhance retrofit evaluations and support cost-effective energy improvements in existing buildings.