How well are energy performance objectives being achieved in renovated apartment buildings in Estonia?

Abstract

In Estonia, the majority of multi-storey apartment buildings were built during the period between 1960 and 1990. Systematic refurbishment of residential buildings on an energy-efficiency basis began in the 2000s, when the energy performance regulation came into force, although the main reason was to save on energy costs.From 2010, the Estonian Ministry of Economic Affairs and Communication fund, KredEx, started supporting the renovation of apartment buildings. A grant scheme which was established in 2015 is related to targeted energy performance certificate classes.In this study, we analyse how well the energy performance targets are being reached following major energy efficiency-related refurbishment work on buildings and how big the performance gap is between measured and calculated energy consumption levels, along with an analysis of the reasons for any differences. The analysis is based on collected energy consumption levels and indoor measurements. In order to analyse heating energy consumption levels, we have constructed simulations of indoor climate and energy use in fifteen renovated apartment buildings.We found that in most cases, the calculated heating energy consumption levels in the design phase were much lower than the measured values have shown. In addition, we discovered that re-simulated values with the same thermal transmittance values are, in most cases, up to 50% larger than heating-related energy consumption levels in the design stage. From this knowledge, we can say that predictions for energy performance levels following refurbishment are too optimistic. For the future, we recommend calculating heating energy consumption levels with the use of a multi-zone simulation tool or by developing a better simplified calculation tool for renovated apartment buildings. In addition, we found out that the reason for heating energy consumption levels being higher following refurbishment work is due to higher indoor temperatures.