Air Tightness

Air Tightness Testing

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AIR TIGHTNESS TESTING STARTS FROM £75**

07771 662357

Air Tightness Testing

What is an Air Tightness Test?

Part L1A of the Building Regulations requires that all New Domestic Dwellings must have an Air Tightness Test once they are completed to determine the air leakage rate of the building.

Also know as Air Permeability / Air Leakage / Air Flow testing

Air leakage occurs through gaps and cracks in the building fabric which allows heat to escape and can have a significant impact on heating bills and CO2 emissions. It can also damage the building’s structure and insulation as warm moist air will condense when reaching colder surfaces within the building fabrics.

 

The more 'air-tight' the building is the easier it will be to heat and keep warm as it is more 'insulated' from the cooler outside environment. The property will be warmer, easier to control, and less draughty, leaky and damp. Generally, it will be more comfortable and energy-efficient to live in.

 

Very air-tight buildings may require more sophisticated ventilation systems and extreme examples are 'Passivhaus' which are so air-tight and well insulated they often require no (or very minimal) heating systems so can be extremely cheap to run.

Why test the air tightness?

The results from the Air Test are used in the final SAP Calculations and can affect whether the building achieves its Part L compliance targets or not and the final energy rating for the building shown on the EPC.



Domestic dwellings undergoing Retrofit Improvements to PAS 2035 many also require Air Tightness Testing performed before, during and after works have been completed. This is to measure, test and check the quality and effectiveness of the improvements being made. Testing for leaks, gaps and, draughts in the fabric whilst work is progressing can be a lot less costly than finding problems once the works are completed and having to 'undo' some of the decorative work that has already been done.

Frequently Asked Questions

  • What is an Air Tightness Test?

    The building is sealed and a large fan placed in an external doorway builds up pressure within the building, once it stops the pressure begins to drop as air escapes from gaps and cracks in the building and how long it takes to return to normal pressure determines how ‘air tight’ the fabric of the building is.

  • Where does air leakage occur?

    Typically, air leakage occurs around pipes, flues, windows and doors but can be anywhere even through the fabric of the building itself, particularly if insulation is missing or has not been installed correctly. Using small ‘smoke generators’ it’s usually possible to locate significant leaks which might be repaired during the test in order to obtain a good air test result on the day if not a re-test will need to be scheduled.

  • Does air tightness affect the fabric and structure of a building?

    When warm air escapes through gaps and cracks in the building fabric it deposits moisture onto the colder surfaces it reaches (warm air holds more moisture than cooler air) which can lead to damp occurring within the layers of the building fabric (interstitial condensation) that can be very hard to trace and treat. Over time this dampness will attract mould which as well as further damaging the building fabric will create an unpleasant and unhealthy living environment.

  • How do I achieve my target?

    There are air tightness targets show in the Part L1a of the UK Building Regulations which are relatively easy to achieve (assuming the regulations are followed) however the more air-tight a building is the easier it is to heat and keep warm and the better energy rating it will achieve on the EPC. Very air-tight buildings may require different ventilation systems to ensure adequate air flow through the building.

  • How airtight does the building need to be?

    Part L1a of the UK Building Regulations require new buildings to achieve an Air Permeability rate no higher than 10 m3/hm2 at 50 Pa.


    At design stage we will assume that a new building will achieve a rate of about 5 m3/hm2 at 50 Pa which is about average.

  • When do I get an air test carried out?

    An air tightness test should be carried out once all the works have been completed on the property and whilst the final As Built SAP Assessment is being conducted. The results of the Air tightness Test will be required for the SAP Assessment but may need to be repeated if the SAP indicates that there are other compliance issues and further works need to be done.


    Ideally the Air tightness Test and the SAP Assessment can be done together by the same organisation so that they can be effectively coordinated.

  • What are the key areas to ensure are airtight?

    • External envelope completed
    • All windows, door & loft hatch fitted and frames sealed
    • Trickle vents, exhaust fans and ventilation grills to be fitted and closed
    • Second fix, plumbing and electrics completed
    • All sanitary ware traps to be filled with water
    • Fireplace & flues sealed.

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