With increasing knowledge about the indoor climate in recent years, preventive methods to avoid health problems caused by deficient building performance may become preferable to reactive methods. Benefits from preventive actions have been suggested for late building design phases, construction, and building operations, however, few data are available that demonstrate the benefits of preventive actions in early planning phases.

In a case study, expected building performance in respect to indoor air quality and thermal conditions in a large judicial facility in North America was evaluated retrospectively at the end of the schematic design and substantial completion phases. A process for evaluation of building performance at schematic design is developed from existing procedures for building diagnostics in operating buildings. Criteria for evaluation of expected building environmental quality at schematic design as available from standards and guidelines are presented.

The results of the study show that building diagnostics at schematic design can be an effective mean of prevention of occupant health problems. Further findings indicate that the assurance of indoor environmental quality can be improved, if the criteria for expected building performance are defined and complied with from early on. It is concluded that implementation of building diagnostics in early project phases can reduce the likelihood of adverse health effects in operating buildings.