Vertical Extension of Buildings as an Enabler of Energy Renovation

We report on the study of six similar buildings built in an area of Gothenburg, Sweden, in 1971, which are now in urgent need of renovation. However, the owner of the buildings - a municipal housing company did not achieve a financially viable renovation of the pilot project. This meant that renovation on a similar basis for the remaining five buildings would not be possible. For this reason the housing company chose to undertake a vertical extension, by adding two floors with apartments on top of the existing buildings. This has improved the economics and made renovation of the five buildings possible. The objectives of this study are therefore, to show how a vertical extension can make a renovation of these buildings financially viable. We argue that a vertical extension can be applied to other similar buildings from this era. If vertical extensions could make more renovations possible this would lead to a significant impact on final energy use and carbon emissions. This case study has been supported by a site visit, interviews with the housing company and the contractor, document analysis, energy simulation and global warming potential simulation. Four renovation concepts are compared in order to find the most appropriate: minimalist, code-compliant, low-energy and low-energy plus vertical extension renovation. The conclusion of this study is that vertical extensions provide enough incentive to preform extensive energy renovations, which could reduce final energy use by more than 50%.