Air Tightness Testing N.I.



Reducing Carbon Emissions : Part F is a vital part of the Government’s strategy towards achieving the UK’s carbon emissions reduction targets. Air leakage accounts for a large proportion of the energy wasted in buildings.

Reducing Energy & Plant Costs : Reduced air-leakage is in the interests of building's owners and/or occupiers as substantial savings in both heating and cooling costs could result.

Protecting the Building Fabric : If warm, moist air is allowed to leak into the external wall cavities of a building, it will tend to cool and form interstitial condensation. This builds up over time leading to breakdown of insulation, damp patches and deterioration of the fabric,

Increased Comfort : A reduction of draughts leads to a warmer house hence more comfort for its occupants.

Typical air leakage paths

House Leakage Image

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.

  • 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.



Fault Diagnosis

In the event of a building failing its air permeability test, the priority becomes finding the sites of excess leakage to enable remedial works to take place.

Localised Smoke Testing

While this procedure is the more laborious and time consuming diagnostic technique, we believe it to be the most effective as it pin-points the individual leakages sites, where they need to be addressed - inside the building