Building occupancy as an aspect of energy efficiency

New Ways of Working was a conjoint research and industry action to better understand the changing nature and requirements of knowledge work that have implications for facility management, productivity and environmental impacts. Currently there are no more fixed times and places for work. Mixed work time and free time, remote work from several locations and collaborative work are clear trends. This paper evaluates methods to understand how office buildings are used and when and where knowledge work is done. Different ways to include building use in assessment of energy efficiency are compared. A key question is how to monitor building occupancy. This paper compares some methods with rough estimations on their reliability. One technology is used in a case study to track workers' presence in an office building. Measurement results are combined with simultaneous walkthroughs and surveys based on self-evaluations of the building users. The results show how the spaces are used, and how reliable the technology and self-evaluations are. The effects of building occupancy on energy consumption are simulated. This paper suggests that building occupancy should be a parameter of energy efficiency and compares alternative indicators to do so. Building occupancy is affected by occupation density (m2/person), occupancy times (hours of occupancy per day) and occupancy levels (percentage of occupants present at a given moment). The traditional indicator of energy efficiency kWh/m2 is flawed when favouring low occupation density, low occupancy time per day and low occupancy levels. Reliable data on building occupancy can be used for several purposes. Savings in energy consumption can be achieved through optimization of building automation systems. An organization can reduce the need for spaces which lowers the costs and the environmental footprint of its facilities. It can also design workspaces that correspond better to the needs of its employees thus improving wellbeing and productivity. Real time data on building occupancy is also useful for security purposes