Occupancy measurement is a special kind of observational research (see previous page) that is targeted at measuring the quantitative usage of spaces. Typically, occupancy measurements record how long spaces are being used, and by how many people. Occupancy measurements can be very useful as input for the briefing process. In an office building, for example, measurements may show that meeting rooms are only used 50% of the time they are available and that these rooms are frequently used by fewer people than the rooms can accommodate. Such data suggest that the organization could do with fewer and smaller meeting rooms, which is obviously relevant input for the brief. There are different ways of conducting occupancy measurements. The most basic way is to have a number of observers (often cheap labour such as students or interns) making rounds in the building, or parts of it, noting whether spaces are used or not. For office buildings, such counting is usually done four times a day. In an educational building, measurements may take place every hour, depending on teaching schedules.Occupancy measurements can also be done by digital sensors that can be placed in the ceiling, underneath desks or even in chairs. Such systems tend to be quite expensive, but they deliver continuous and fine-grained data. When analysing occupancy data, it is important to distinguish between different kinds of metrics. There is average occupancy (occupancy levels averaged over a period of time), peak occupancy (the highest occupancy level measured) and modal occupancy (the most frequently measured level of occupancy). When looking at average occupancy only, one can get the impression that it is possible to radically cut back on space consumption, which can be somewhat misleading. For example, if the required number of meeting rooms is based on their average occupancy, this may very well lead to disgruntled employees on Monday mornings when everyone wants to have their meetings. Conversely, calculating with peak occupancies may result in large numbers of spaces that mostly stand empty. Consequently, it is usually the modal occupancythe situation that is most commonthat is the safest to use for capacity calculations. Recommendations-Communicate clearly when and why the occupancy measurements will take place.-Make clear that the measurements will not be used to collect any data about individuals.-Look carefully at the measurement period (e.g. avoid holidays).-Be aware that occupancy measurements show current usage, based on existing behaviours and technologies. Future use patterns may be different.-Combine occupancy measurements with interviews in order to be able to interpret the outcomes (Why are certain spaces intensively used or underutilized?).-Examine to what extent occupancy peaks can be reduced by spreading activities more evenly in time (e.g. scheduling the use of lecture halls over a larger period of time).