Blower Door Test

A Blower Door Test is also known as a Pressurisation Test or a Permeability Test.

A blower door is a device which measures the airtightness of a building. It is also useful in helping to find the location of air leaks through the building fabric (gaps or cracks in walls, roofs, floors etc.). Door blower tests are mandatory for newly constructed houses and apartments where substantial work commences on or after 1st July 2008.

The Importance of Airtightness

The airtightness of a building has an important effect on comfort, heating costs and indoor air quality. Obviously, a leaky building costs more to heat and is less comfortable for occupants. At the same time, a building that doesn't have sufficient ventilation is not desirable because lack of fresh air results in poor indoor air quality for occupants as well as the build up of moisture which can cause mould growth and deterioration of building materials and finishes. Therefore, a balance needs to be achieved between having the minimum heat loss possible and adequate ventilation.

The Testing Device

A blower door consists of a large variable-speed fan, an adjustable steel frame and fabric cover that temporarily fits in an external doorway, pressure gauges and electronic equipment that record the test results.

Testing Procedure

The test is performed with all external doors and windows closed apart from the doorway where the test is being carried out. Any open flues (such as chimneys) or ventilation openings are temporarily sealed (see photo). All internal doors are kept open so as not to impede the free flow of air inside the building.

Since the test de-pressurises the house, sucking air in through all openings, it is important that all combustion devices be disabled during the test. Heating systems and gas water heaters must be switched off. Any pilot lights should be extinguished. All wood-burning appliances in the house need to be off, which requires prior notification for occupied houses during the heating season (October - March).

The accuracy of the test can be affected by wind because the pressures the blower door fan exerts on the building are relatively small. In general, windless conditions are best and gusty conditions are more difficult.

Multiple measurements are taken by adjusting the speed of the fan. Multiple readings are taken over a wide range of pressures. The readings are then averaged using special software to give more accurate results.

Air Change Rates

Building Regulations 2008 TGD-L (Dwellings) indicates that reasonable provision for airtightness is to achieve a pressure test result of no worse than 10m3/(h.m2)@50Pa

Building Regulations 2008 TGD-L

Below is a table of air changes per hour (ACH) results for buildings of various standards

We use Infiltec Blower Door Testers for performing our tests