Air tightness testing (domestic)

Air tightness, air leakage and air permeability all refer to the infiltration of air into the building and/or the loss of air from inside through gaps, cracks, holes etc in the building fabric. Air coming in and out of a building may lead to reduced energy efficiency, lost heat and cold draughts. Such testing is mandatory for developments of more than two dwellings. Common areas for air leakage are:

  • service penetrations - supply and waste pipes, sockets and switches, light fittings
  • fitments - windows and doors, loft hatches
  • construction - corners of walls, abutment of walls, floors and ceilings.

Air tightness tests take place once the building is complete, at least to the extent that any remaining work will not affect air tightness.

Dwellings will pass the air tightness test if the measured air permeability is equal to or less than the design air permeability. The worst design air permeability is 10m³/(h.m²) @ 50Pa. View our Icon for pdf air sampling rate [73.57KB] for guidance. A dwelling will fail an Air Tightness Test if:

  • the measured air permeability is worse than the limit value of 10m³/(h.m²) @ 50 Pa, or
  • the Dwelling CO 2 Emissions Rating calculated using the measured air permeability is worse than the Target CO 2 Emissions Rating.

Any dwelling that fails an air tightness test will require remediation work, a re-test and an additional test on another dwelling of the same type will be required.

The loss of this 'conditioned air' through the 'uncontrolled ventilation' may affect the energy consumption of the building as additional energy may be required to re-heat or re-cool the air. Building air tight structures will save energy and money, improve comfort and reduce the risk of damage to the building fabric itself. Airtight does not necessarily mean stuffy, good controlled ventilation is vital for health and comfort.

As qualified air tightness testing engineers registered with the Air Tightness Testing and Measurement Association (ATTMA), we can advise on where buildings are prone to leaking and how to seal any leaks correctly. This assessment is focused upon conservation of fuel and power usage. The (de)pressurisation testing is based on BS EN 13829:2001 and ATTMA Technical Standards using UKAS calibrated equipment.

We offer a friendly and reliable service and are happy to provide quotes when multiple tests are required, which may include a discounted rate. Please use our energy enquiry form for one of our qualified assessors to get in touch.

Guidance from ATTMA

The Air Tightness Testing and Measurement Association (ATTMA) have produced a number of guidance documents that you may find useful:

Pre-test information and requirements

All services provided by South Holland Building Consultancy are covered by our standard terms of business and shall supersede and override all other warranties, representations, terms and conditions whether express or implied, oral or written, including the Client's standard terms.

For information, please refer to South Holland Building Consultancy's standard terms of business.

Air tightness testing explained

Air tightness testing, sometimes known as air leakage testing, is the process of measuring the uncontrolled air flow through gaps and cracks in the fabric of the building. Too much air leakage leads to unnecessary heat loss and discomfort to the occupants from cold draughts. In order to determine the level of air leakage, a fan is installed into the external envelope and the amount of air flowing into or out of the building over range of pressures is measured using calibrated equipment.

For more information, please refer to the ATTMA Technical Standard for Measuring Air Permeability in the Envelopes of Dwellings.

Building condition

When determining whether the building is ready for testing, the following points should be considered as the minimum condition requirements:

  • All drainage traps in toilets, sinks, baths, showers and wet rooms should be filled with water.
  • All incoming and outgoing service penetrations should be made and permanent sealing works completed around penetrations.
  • All trickle and combustion vents should be fitted and closable.
  • All external doors, including integral garage doors, should be fitted with seals and closable.
  • All external windows should be fitted with seals and closable.
  • All plug, television, data and satellite socket plates should be fitted without items plugged in, other than those required for the operation of the air tightness equipment.
  • All lighting switch plates should be fitted.
  • Electrical power is available to the plot.

For more information, please refer to ATTMA are you ready to test?

Disruption and damage

Site activities undertaken by other trades working in or around the building are likely to be disrupted for the duration of the test as access and egress will be restricted. The air tightness test is a non-destructive procedure; therefore, the risk of damage to fixtures and fittings is negligible. However, the client or the client's representative should ensure all fixtures and fittings are secure prior to the commencement of the test.

Weather conditions

Extreme weather conditions, such as high wind speeds, can have a detrimental effect on the result of test; therefore, if inclement weather is forecast on the proposed test date, the test technician will liaise with the client or the client's representative to discuss the consequences of continuing to test and if necessary reschedule.

Temporary sealing

Air tightness testing measures the uncontrolled air flow through gaps and cracks in the fabric of the building, not the designed ventilation, such as trickle vents and mechanical extractor fans. Therefore, it is a mandatory requirement to close and temporarily seal designed ventilation. All temporary sealing will be checked and recorded prior to commencement of the test.

For more information, please refer to ATTMA temporary sealing guidance for dwellings.

Reporting and certification

On completion of the air tightness test, a provisional result will be provided to the client or the client's representative. It should be noted; this result is interim and should not be used for compliance purposes. Within 5 working days, and subject to further checking, an authorised lodgement certificate, together with a report if the test was satisfactory, will be issued confirming the result. The lodgement certificate should be forwarded to the Building Control Body.

In the event of an unsatisfactory test result, the client or the client's representative is responsible for sealing all identified air leakage paths. It should be noted; any additional temporary sealing or deviations from the ATTMA technical standard will be subject to a quality assurance review and may be considered unacceptable.

On completion of remedial works, the client or the client's representative, is responsible for arranging a re-test, for which an additional fee will be payable.

Should you require further information or assistance, please contact us by calling 01775 764616 or email