Rebound effects projected onto carbon footprints - Implications for climate change mitigation in the built environment

Climate change mitigation in the built environment encompasses various mitigation measures, such as energy efficient buildings, spatial planning instruments and other policies targeting the emissions resulting from transport. However, studies on the impacts of these measures typically only focus on a single emission source, such as housing energy or transport. The thesis enlightens, why the focus on the targeted emissions alone is misguiding in many cases. The key concept of the thesis is the rebound effect. While mitigation measures often reduce the targeted emissions, they have unintended consequences due to shifts in consumption. These unintended consequences are called rebound effect. The thesis contributes to carbon footprint research in the built environment and supports the earlier findings that urban structure has a weak or even statistically insignificant connection to total carbon footprints, despite having a relatively strong effect on driving-related emissions. The thesis explains this phenomenon via the rebound effects for reduced car ownership and driving, but also by means of other issues covered in the thesis. In Finland, which is the geographical scope of the thesis, the benefits of intra-household sharing are stronger in suburban areas than in inner urban areas, which alleviates the harmful effects of urban sprawl. Furthermore, new energy efficient housing has reduced carbon footprints in outer urban areas but not in inner urban areas. While the effect of urban structure appears low, direct reduction of driving, energy efficient housing and the sharing of greenhouse gas intensive goods and services seem to reduce carbon footprints significantly. The thesis aims to bridge the gap between studies on theoretical rebound effects and studies on empirical carbon footprints within the context of the built environment. Rebound effects are usually studied with econometric modelling, whereas carbon footprint studies are based on the real expenditure of consumers. A carbon footprint-based definition for rebound effect is presented as the theoretical implication of the thesis. This graphic presentation could be used for rigorous empirical testing of rebound theories by using carbon footprints when longitudinal data are available. In practice, the thesis demonstrates the ways in which cross-sectional carbon footprints can be employed to estimate probable rebound effects.