Environmental impact of retrofitting second homes: A case-study of the net global warming potential of different retrofit measures in a Swedish context

Abstract

The building and construction sector is responsible for a fifth of the greenhouse gases released by human activities, and retrofits are promoted by the IPCC as an effective way to reduce the energy consumption and hence environmental impact of buildings. Retrofits initially implies an increased environmental footprint associated to the addition of materials and activities that are then successively compensated by the expected savings in operational energy. For permanent housing this trade-off normally implies a decreased life cycle environmental impact, however this study focuses on second homes. What separates second homes from permanent housing is that they are used intermittently, typically during weekends or vacations, hence suggesting that the compensation for a footprint caused by a retrofit takes longer. This thesis compares the added environmental impact of three common retrofit measures to the reduced impact from the lower operational energy following each retrofit respectively. The analysis is performed on three different case houses in southern Sweden, and the studied measures are changing windows, addition of roofinsulation and installation of an air-sourced heat pump. The difference between the impact embodied in a retrofit measure and the reduced impact from operational savings is referred to as the net environmental impact. The findings suggest that it is not environmentally preferable to retrofit second homes, but rather to keep a low indoor temperature while not using the house if it can can be assured that this does not cause any risks or damages to the house.