Buildings are expensive resources. For many clients they are their second-most expensive resource, with only their staffing costs being higher. This is why efficiency is an important topic in almost any brief. There are different kinds of efficiency that can be addressed in relation to building design (energy efficiency, maintenance efficiency, etc.) but in the briefing process, space efficiency will the most important as it is directly related to the overall size, and thus the budget of the project. Space efficiency is essentially about asking for no more space than is needed. The first obvious thing to look at is the size of the requested spaces. How much space is needed for the functions that have to be realized in the building? For example, should the size of an office workstation be 6 or 8 square metres? Or: should a single-bed hospital room be 11 or 12 square metres? Such questions may seem to focus on details, but if a project consists of hundreds of workstations or hundreds of patient rooms, the answers will have a large impact on the total space requirements. It therefore makes good sense to look critically at the space needs of such functions, for example by conducting prototypical design studies of different concepts. The second way to achieve space efficiency is to look at the utilization of spaces. In office projects in particular this is a hot issue. It has become received wisdom that desks tend to stand empty for a large part of the time they are available. New concepts such as free seating and activity-based working help to improve the utilization rate of workplaces and can have quite a dramatic impact on the overall need for space, reducing it by up to 20 or 30 per cent.Efficiency, however, should always be balanced against quality. In an Excel sheet, it is all too easy to improve efficiency by tweaking the quantities and sizes of spaces. The end result, however, may be spaces that are too cramped or too crowded to work in, thereby having a negative impact on peoples well-being and performance. Efficiency should thus never be considered in isolation, but always in relation to the usability and functionality of the building.Strategic brief-Develop a space budget for the entire building, based on the number of functional units (e.g. workplaces or beds) or users (e.g. office workers or patients).-Consider the possibilities for intensifying the use of space (e.g. free seating for office areas).Functional brief-Take a critical look at the spatial needs of different functions: are there possibilities for the shared use of spaces, the intensification of use, or the multifunctional use of spaces?-Conduct prototypical design studies to establish whether the assumptions made about the size of spaces are valid.Technical brief-Look into other kinds of efficiency such as energy efficiency and the operational efficiency of the buildings technical services.