Energy retrofit of multifamily residential buildings: status, case studies and potential for Geneva

Pierre Hollmuller Head of Systèmes Energétiques Group

Abstract
This study focuses on energy retrofitting of multi-family residential buildings in Geneva, integrating technical, economical, financial and environmental aspects, as well as preservation of cultural heritage.
The first part of this study shows that multi-family residential buildings in Geneva are responsible for almost half of the thermal energy consumption of the canton as well as half of the CO2 emissions of all the building stock. About half of this consumption and these emissions are caused by post-war multi-family dwellings built between 1946 and 1980, which are nowadays in need of retrofit. The analysis of retrofit dynamics registered between 2004 and 2012 shows a significant increase in energy retrofitting of residential buildings since 2010.
The second part of this study deals with the real performance of retrofit actions, with a focus on energy and economic aspects. The study is based on a monitoring campaign implemented in a multi-family building built in 1963 in Onex (GE) that was retrofitted according to the Minergie standard in 2008 and a benchmark study over 10 buildings retrofitted between 2006 and 2009. The assessment of the energy performance of these actions shows that the real space heating demand of the retrofitted buildings is 43% to 142% higher than the expected calculated value. The economic analysis shows that, for achieving the Minergie standard of the post-war multifamily building stock, the global retrofit cost (energy and non-energy related) would be around 10 billion CHF.
The last part of this study evaluates the theoretical energy saving potential for space heating in Geneva’s multifamily building stock and provides concrete recommendations to mobilize efficiently this potential. The main conclusion is that the achievement of the ambitious goals set by the federal government is hardly possible without an improvement of the current practices regarding the actors involved in building retrofit process.

Author: Khoury, Jad.

Note: This result was developed outside of the Renowave project.