Energy efficient retrofit of an end of the row house: Confronting predictions with long-term measurements

Looking to the EU's 20/20/20 program, energy efficient retrofitting will be a key element in the 20% less primary energy in 2020 compared to business as usual. Within that context, field studies that put realizable efficiency in perspective are urgently needed. The dwelling evaluated was built in 1957. In those days energy efficiency was no concern. Houses got no insulation, ventilation was adventitious and heating systems scored badly. The retrofit started in the early eighties, stepwise as to follow the impact of separate measures on heating energy consumed. A solar boiler was installed in 2004. PV followed in 2009. The first 19 years a family of five inhabited the dwelling, then the parents only. Monitoring started in 1978. In the paper, predicted annual energy for space heating is compared with monitored result. The measured data, though showing a net decrease, consistently underscore predictions. Main reason is direct rebound. The benefits of the solar boiler and PV-panels are minimal compared to the energy avoided by better insulation, energy efficient windows, better air-tightness and upgraded ventilation and central heating. However, targeting passive house and zero energy quality is beyond optimal in terms of net present value and not doable in the dwelling. (C) 2010 Elsevier B.V. All rights reserved.