Why we air test: Domestic energy accounts for 28% of carbon emissions which contribute to climate change.

The Government has set targets to reduce this figure in line with the Kyoto Agreement. In order to meet this reduction the Government amended the Approved Document L1A of the Building Regulations. Approved Document L1A sets targets for all new dwellings in terms of their CO2 emissions which are known as the Dwelling Emission Rate (DER).

Air leakage (which is a measure of uncontrolled air through gaps) from a building is a major cause of energy loss and contributes to the increasing levels of CO emissions.

As part of the calculations to determine the DER, a maximum air leakage rate is obtained. The highest amount of air leakage under the approved Document L1A is 10m3/h/m2 at a pressure difference of 50 Pascals; however, this may have to be reduced in order to pass the DER if the architectural design of the dwelling dictates. This may have to be as low as 7, 5, or even 3 m3/h/m2.

Who can air test?

In accordance with Building Regulations Approved Document L1A Section 20B, an air tester must be registered with the British Institute of Non-Destructive Testing (BINDT) or be an Air Tightness Testing and Measurement Association (ATTMA) member. The air tester then can issue a certificate which the building control Inspector is authorised to accept. (Please download the document on this page to view a sample of a BINDT certificate)

Air testing procedure

Air tightness testing is carried out in accordance with the procedures detailed in ATTMA TSL1 (Please use the website www.bindt.org for a free download) and BS EN:13829 (2001). ATTMA TS1 describes how to carry out the test and the analysis required to determine the air permeability. Air permeability is expressed as volume flow per hour (m3 h-1) of air supplied to the space per square metre (m2) of envelope area for an internal to external pressure difference of 50 Pa.

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The test involves connecting a fan, or a number of fans, to a suitable aperture in the building envelope and pressurising it over a range of pressure differences. The fan speed is increased in steps up to a maximum and then decreased in steps. Air volume flow rate through the fan (equal to the air leaking through the building envelope) and the pressure difference across the building envelope are recorded at each fan speed. In calculating air permeability, corrections are made for temperature and barometric pressure. Local wind speed should preferably be below three meters per second. If the wind speed is above 13 mph then the air test cannot be carried out.

Before the test is carried out, all mechanical ventilation systems must be switched off. All mechanical ventilation grilles and openings to the outside must be sealed. Sealing can be achieved with plastic sheeting and strong adhesive tape. Smoke vents should be closed but not sealed. Drainage traps should be filled. (Please download the document on this page to open our pre-test checklist).

Areas that should be sealed for a test

  • mechanical ventilation
  • open boiler/fire flues and air supply grilles
  • passive stack ventilation systems with automatic/no dampers
  • external windows/doors
  • actual extractor fans/cooker hoods
  • air bricks
  • trickle vents to doors/windows

Areas that should NOT be sealed for a test

  • external cavity ventilators
  • letter boxes
  • key holes and cat flaps
  • seals to drains and overflows
  • penetrations through walls e.g. outside taps
  • tumble dryer vents
  • balanced flues
  • seals to loft hatches

While the pressurisation test is being carried out all external doors and windows must be closed and secured to avoid them being blown open. Internal doors must to be wedged open during the test to avoid them slamming shut. The fan unit will create draughts in the building. Lightweight objects and paper near the fan unit should be removed or covered to avoid them being blown about. Fixtures and furniture will not be affected.

Access in and out of the building during the test will not be possible (unless there is an emergency and a need to evacuate the building). The test will take approximately 90 minutes. Site workers can remain in the building during the test, or will have to remain outside until the test is complete. There are no health risks to site workers who remain in the building during the pressure test, however there may be some discomfort due to cold draughts and some noise from the fan.

Once all the data has been obtained, this is then entered in to a computer which will then calculate the final results. These are then given verbally to the customer/applicant. If this is under the Dwelling Emission Rate (DER) then the dwelling has passed the test. If the result is greater then the DER then the dwelling has failed the air test. If the dwelling has failed an air test, we will identify areas of air leakage using a smoke pencil for the customer to rectify.

Within seven days of carrying out the air test a detailed report will be sent to the customer/applicant stating the results and test data. The report may also contain photographs identifying the problem areas (Please open the document below to see a sample of a report). The report may also include the official BINDT certificate which is required to be passed to the relevant Building Control Authority, however if Doncaster Building Control is the inspecting Authority, the BINDT certificate will be retained.


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Last updated: 27 July 2023 07:07:24

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