Airtightness Measurements in Two UK Office Buildings Available to Purchase

A major factor in the ventilation of buildings is the leakiness of the building envelope. In housing, it has been possible for some time to measure leakiness quickly and easily by using a fan (sealed in place of the front door) to pressure/depressurize the building. Until now, this has not been done in larger buildings either in the UK or elsewhere in Western Europe.

The Building Research Establishment (BRE) designed and built three fan units which can be used together to pressurize large nonresidential buildings. A novel feature of the pressurization rig is that the fans are powered from conventional 13-A ring mains. This is in contrast to the techniques used in North America of either using a building's mechanical ventilation system (not possible in the UK since most buildings are naturally ventilated) or a large, bulky, trailer-towed fan with its own generator.

Envelope leakage tests have been carried out in two medium-sized (approximately 5500 m³) office buildings. Pressure differences of well over the accepted target of 50 Pa between inside and outside were reached easily.

Results showed that one of these buildings, of conventional construction, was twice as leaky as those found (on average) in North America. The other, built specifically as a low-energy office at BRE, was found to be as tight as the North American buildings. BRE will carry out measurements in further buildings as an aid to understanding and developing air leakage control from the viewpoint of natural ventilation.