The test involves connecting a fan to a suitable aperture in the building envelope (i.e. an external doorway)
and taking a range of pressure difference readings. The fan blows air into (or out of) the house to create a slight pressure
difference between the inside and outside of the dwelling.
By simultaneously measuring the air flow through the fan and its effect on the air pressure in the building,
the system measures the air tightness of the entire building envelope.
All tests are carried out in accordance with ATTMA TS1
(Technical
Standard 1: Measuring air permeability of building envelopes).
A typical air test involves a number of steps:
One of our engineers will take a walk around the building and ensure that all pre-test requirements have been met and
the building is in a fit state to be tested. This involves ensuring all ventilation openings are either closed,
or if they can’t be closed then sealed.
Internal and external temperature, barometric pressure and
wind speed is measured before the test begins.
The fan is installed into a blower door frame, fitter into a
suitable aperture.
With the fan covered a recording is taken of any pressure
differential which may exist between the inside and outside of
the building
The fan is uncovered and the airflow rate is increased until
a pressure difference across the envelope is achieved of about
10 Pa.
The pressure difference is then increased in incremental
steps of 10 Pa (usually up to 60 Pa) with measurements taken at
each step.
The flow rate is then decreased in steps, taking further
measurements at each step.
The fan is then covered and the static pressure is recorded
again.
Internal and external temperature, barometric pressure and
wind speed is then measured again.
The results are then processed and the correlation between
the values taken at the various pressures allows the air
leakage rate to be determined.
Extractor inlet being sealed (ventilation sealed if cannot be closed)
