CONSEQUENCES OF DEVIATIONS BETWEEN SIMULATED AND MEASURED ENERGY USE in retrofitted projects

Sammanfattning: For the next 40 years, a rate of 3% of the European building stock per year needs to be renovated in order to meet the carbon and economic goals set out in the European Economic Recovery Plan. This puts high demands on the accuracy level of energy simulations software for predicting the energy need for retrofitted buildings. However, in most cases the simulated energy need does not correspond with the actual measured energy need, a crucial error which need further investigation. Three similar multi-residential buildings built in from the 1970s were chosen as case studies. The reports showed a deviation from simulated and measured energy need are respectively 24.7, 18.3 and 2.4 %. This thesis has its focus on the process of how misjudged parameters will impact the results of energy simulations in connection with retrofitting projects. Each parameter was assigned with a maximum and minimum value between which it could fluctuate based upon findings during a thorough literature study. The deviation on the total energy need was documented and a Life Cycle Cost was conducted for each parameter in order to demonstrate the economic impact of a misjudged aspect. In order to improve the level of accuracy, methods was developed for each parameter to refine the simulation input. The following parameters were addressed: • Area deviation • Air-tightness/leakage • Wind • Thermal bridges • Heat recovery efficiency • Indoor temperature variation • Losses in hot water circuit system • Domestic hot water need • Tenant electricity need • Utilization factor The SVEBY standard was implemented to investigate uncertainties connected to user behaviour. The final result for the deviation between simulated and measured energy need was drastically reduced to less than 10% by implementing the developed procedures. Among the 10 parameters which the Life Cycle Cost took into consideration, the user behaviour aspects had the highest impact on the energy need. Generally domestic hot water had the largest impact on the net present value (NPV) ranging between 341-477 SEK/m².