With good design practices and life-cycle cost optimization, the specific fan power for individual (SFPI) fans will be between 0.5 and 1 kW m(-3) s(-1). Data from nearly 1000 audited fans in Sweden show that the average measured SFPI weighted by drawn motor power is 1.5 kW m(-3) s(-1), and the situation appears to be similar in other countries. Contract forms used by Swedish builders and consultants＇ design practices are analyzed here to search for an explanation of the low performance of installed systems. Identified as two major barriers to efficient system design are the lack of performance specifications when procuring systems and the incentive structure in the building sector. As a consequence, duct design methods, rules of thumb, and vendor recommendations do not lead to system optimization. The broad minima in life-cycle costs over a range of air-handling unit sizes show that potential economic welfare losses from efficiency standards are likely to be smaller than the losses that result from today＇s design practices.