Uncertainty in Energy Simulations of Multi-family Dwellings

Since energy simulations are used to verify that projected residential buildings will reach the current energy requirements it is important that the results are reliable.This report investigates the extent of uncertainty in energy simulations, estimates the causes of the uncertainty and its economic and environmental consequences. The method used in this report is based on three validation methods; empirical validation, analytical validation and comparative validation. The analysis was carried out for five multi-family dwellings in Uppsala with installed meters for energy measurements. One of these objects, Klockarlunden, was studied in more detail than the others. The results show that the deviations are between 10 and 29% for the studied objects, which means that the uncertainty is estimated to be at least 29%. All simulations underestimate the buildings need of energy. The simulation for Klockarlunden can predict the energy consumption to be within the range of 46-98 kWh/m2year with 90% confidence level based on the current uncertainty. The range equals a standard deviation of 28% of the mean. The origin of the uncertainty for the studied objects was shown to be due to weak estimations of hot water consumption, ventilation flow rates, leakage and household electricity. The consequences of the difference between simulated and measured energy consumption can be translated to SEK 8.5 million and 4.5 thousand tons of carbon emissions over the estimated economic lifespan of the buildings