Air Leakage / Heat loss

A significant contribution to heat loss in a building can be caused by poor levels of airtightness. The economic consequences can be increased fuel bills and system running costs caused by heating systems having to work harder than necessary to keep the building at a satisfactory temperature. Relatively minor air leakages in a building can lead to draughts and discomfort for householders, patches of condensation on walls and inefficient energy performance. Identifying the source of a draught can be difficult with the air leakage paths often hidden by kitchen units, bath panels or other boarding.

Pressure testing uses a fan system to depressurise the building. The system is fitted into a frame sealed within an external opening such as a doorframe. Mechanical ventilation openings are sealed with polythene sheet and tape or other appropriate materials. Smoke extract fans/vents are closed but not sealed, and other internal openings (e.g. lift shafts) are left unsealed. As the building is depressurised, colder air is drawn into the building through gaps, crack and holes in the building fabric. These may be visually noted, identified by the use of smoke pencils or recorded on a thermographic image.

Combining a blower door test with thermography in this way, enables a systematic recording, with visual evidence in the form of thermograms and photographs, of air leakage paths, which can be combined with annotated floor plans in a report if required.