Assessing building performance in use 3: energy performance of the Probe buildings

By early 1999, the Probe series of post-occupancy studies had reported individually on 16 buildings. This paper compares their energy performance and carbon emissions (for technical performance and occupant satisfaction, see papers 2 and 4 in this issue). All but one building (which paradoxically used the least energy of Probe's air-conditioned offices) claimed to be energy efficient, but achieved performance ranged from excellent to below average. Across the sample, there was a factor of six in carbon dioxide emissions per unit floor area, and even more per occupant. The air-conditioned buildings tended to use the most energy: they usually contained more equipment, were more intensively occupied, but also usually ran more liberally and wastefully - as did more complex systems generally. Often complication seemed to have been added before the fundamentals had been made efficient. Design objectives were also frustrated by poor airtightness, control problems, unintended consequences, a dearth of energy management, and a tendency for systems to default to 'on' - also a pathological trend for information technology and its associated cooling demands. Solutions include load reduction, 'gentle engineering', better matches between demand and supply, and predictions based on a better understanding of in-use performance.