Comparison of the actual and theoretical energy use in nZEB renovations of multi-family buildings using in situ monitoring

Department of Architecture and Urban Planning, Faculty of Engineering and Architecture, Ghent University, SintPietersnieuwstraat 41, 9000 Ghent, Belgium

^* Corresponding author: stijn.vandeputte@ugent.be

Abstract

Often there is a significant difference between the actually measured and theoretically calculated energy use. The deviation between the two can be a result of errors in design, construction or commissioning, due to the technical performance of building components and installations that don’t meet the design requirements. But equally, incorrect assumptions in the calculation can largely affect the results, for example the user influence that is simulated in a different way. This paper presents the analysis of data from an on-site monitoring system of two case study multi-family buildings that were deeply refurbished. It points out that the calculated energy use for space heating was largely underestimated, while there was an overestimation of the energy use for domestic hot water. The high indoor temperature and the low occupancy of the apartments were identified as the key parameters to explain this striking difference between the theoretical design and the actual situation.