Impact of Building Occupancy on Assessing the Effectiveness of Energy Conservation Measures

Assessing the effectiveness of energy conservation measures (ECMs) prior to their actual implementation in buildings is critical. There is an increasing tendency to employ calibrated building energy models to quantify energy savings that could be achieved by ECMs to justify their implementation. However, there is empirical evidence that reveals noticeable discrepancies between simulated and measured performances of ECMs in buildings. One possible reason for such discrepancies is that actual building occupancy, which is a critical factor that determines the total and peak loads of building systems and related energy consumption, is not represented accurately in most energy models. This paper specifically examines the impact of actual building occupancy on the assessment of ECMs. Two energy models of an office building were built and calibrated with the same audit data following the same procedure, except that one used assumed occupancy and the other used actual occupancy. Both models were used to assess an ECM, which adjusts indoor air temperature set points based on the time of the day. Statistically significant differences were observed in the energy consumptions reported by the two models through paired t-tests. The results highlighted the importance of integrating actual occupancy in the assessment of ECMs.