A comparison of measured and estimated electric energy use and the impact of assumed occupancy pattern

The use of building performance simulation (BPS) tools to guide decisions during the design process in its early stages requires making assumptions. That is as the design specification, information about building use and future external climate are not available. This may lead to differences between the buildings performance in operation and its predicted performance. The aim of the presented work is to assess the impact of the building use on observed differences in performance. Parameters of concern are occupation period, occupancy density, electrical energy use and sensible heat gains from equipment and light fittings. The results of the study show that the difference between estimated and measured local electric energy use is below 10%. The important parameters related to the office use are identified as occupation period and heat gains from light fittings. In case of the considered building the use of medium high internal heat gains would have lead to overestimating the cooling demand by 30%. The identified parameters should be considered with great care when using BPS–tools for guiding the design of office buildings as they contribute significantly to the accuracy of simulation results.