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Air Tightness Testing

Air tightness testing - Air tests, air leakage & air permeability

Air tightness testing is also recognised as air leakage, air infiltration and air permeability testing. The airtightness testing process is a government requirement for any new-build or development. It is important to remember that air leakage should not be confused with ventilation.

The air leakage of the property is due to the uncontrolled flow of air. As opposed to simple ventilation, such as draughts through cracks and gaps within the building fabric.

Air leakage can occur through cracks, gaps and holes within the building fabric. These may not always be obvious or visible. In turn, this affects the energy performance of the building.

This allows heat to escape and will inevitably increase energy bills and the production of Co2 (Carbon Monoxide). In addition, this cause discomfort for the occupants of the property due to the loss of heat.

The airtightness test will provide a result of air leakage per hour. We measure this by per square metre of the external area of the whole building.

Air Tightness Testing 1

How is the air tightness test carried out?

The airtightness testing procedure is carried out under strict guidelines according to iAts ( The Independent Airtightness Testing Scheme ).

We will liaise with you beforehand to select the most suitable time and day for us to arrive on site. We’ll also confirm with you the number of dwellings to be tested. Our engineer will arrive equipped with a fan, or number of fans.

The dwelling to be tested will need to be temporarily sealed while the test is taking place. A suitable external opening selected for the fan to be attached to usually the front door.

All internal doors throughout the property will remain open, this will allow the whole property to be pressurised.

If there is any air leakage, this will show once the building has been depressurised.

At this point, we will use an anemometer to calculate internal and external pressure. This reads the total strength that the fan has to achieve to make up the difference in air pressure within the property.

Many additional readings are taken. This will include additional factors including temperature and barometric pressure. This allows us to calculate the air leakage.

The overall reading is calculated as metres of lost air, per hour and per metre square of the building envelope. This includes the walls, floor and roof area.

The whole air tightness testing process should take around an hour to complete for each dwelling being tested. The result will come in the form of a detailed report and certificate.

For detailed information, please check the article on what is an air permeability test.

We offer: Residential Air Tests | Commercial Air Tests

SAP Calculations

Before the air test is carried out, it is very important for us to have accurate calculations.

These calculation include the buildings external envelope and fabric. You can read more on SAP calculations here.

Why use Ratio Seven for air tightness testing?

In an ideal world, we will have been involved with your project from the design phase. However, we realise this may not always be possible, so we aim to be flexible.

Where we have provided design advice early on, clients have benefited from 100% first-time pass rate. In most cases, the results are obtained on the same day.

Need an urgent air test?

It is also possible to have an air testing engineer on-site with less than 24 hours notice. Please contact us for availability.

Please call us on 01270 747311 or fill in the form on our contact page if you require any further information on air tightness testing.