Passivhaus Member Air Tightness Testing, Ventilation Commissioning

Air Tightness Testing

What is an Air Tightness Test?

Air Tightness Testing also known as air changes per hour, air permeability and air Leakage measures the amount of uncontrolled conditioned air escaping from the interior of a building through gaps, holes and cracks.

Do I need an Air Tightness Test?

Building Regulations (Part L) for domestic & commercial new builds or conversions require that the building meets certain air permeability targets. The method is to carry out an Air Tightness Test. The results of this test will affect the EPC rating of the building with high levels of air permeability negatively affecting the buildings energy performance. Air Tightness Testing is required for all new build properties to ensure the building meets or exceeds the air permeability rating (often refered to as DAP) specified in the design stage SAP calculations.

Air Tightness Test being carried out by accredited air tightness tester

How is the the test conducted?

Once your plans are received and prior to us attending site we work out the envelope of the building in m2 and the volume of the building in m3 (if Passiv/low energy) using 3D modelling. When on site a large UKAS calibrated fan in a expandable frame is placed into the main external door of the building other external doors and windows remain closed with internal doors open. The fan will pressurise/depressurise the building to a pressure of at least +/-50Pa. A UKAS calibrated manometer reads the internal pressure, the external pressure and the strength the fan is having to work to create that pressure difference. A number of readings are taken with other factors such as barometric pressure and temperature which then allows air permeability (Q50) - meters cubed per hour per square meter of envelope (m3/h/m2@50PA) or air changes per hour (N50) - meters cubed per hour per cubic meter of building volume (m3/h/m3@50PA) to be calculated.

Whilst we are conducting your test, other contractors can continue work within the property. However, all windows and doors must remain closed for the duration of the test.

What are the benefits of Air Tightness?

Compliance with current Building Regulations. Click here for PART L
Impacts the buildings EPC rating.
Reduced heat Loss & energy usage.
Lower heating bills.
Lowers C02 emissions.
Stems the spread of fire.
Thermal comfort due to consistent indoor temperatures.
Prevents interstitial condensation reducing the risk of mould growth and structural damage.
Improved, healthier indoor air quality as controlled air ventilation systems will manage pollutants and allergies.

Property envelope calulation for Air Tighness Test, Ventilation Comissioning

Exploded 3D house plan for air tightness testing and ventilation envelope calculations

When Should It Be Carried Out?

Usually you should carry out Air Tightness Testing towards the end of your project unless its a Passiv house or you have specified otherwise.

Site Readiness Checklist - Click here for ATTMA guidance to help you determine when your building is ready.

Temporary sealing - Click here for ATTMA guidance to determine what is/is not allowed to be sealed.

How Long Does It Take?

Once we have worked out your buildings envelope area/volume off site, The actual duration of the test will depend on the building size and the level of preparation undertaken before testing. Generally the duration of the actual test should take no longer than two hours.

What do I get?

Once the test is finished you will be provided with a certificate (within 24hrs of payment) showing the results. This certificate will be lodged with ATTMA which if compliant will also satisfy the conditions of the Building Regulations part L. Passiv/low energy properties will also receive 3D modelled drawings and calculations for their files.

What Happens If My Building Fails?

There are a number of different elements within a building which can affect Air Tightness during construction - ie:

Check sealing around window and door frames.
Replace damaged or missing window seals.
Spaces behind fitted units such as bath tubs or vanity units should be sealed - not forgotten.
Cracks and gaps around sockets and other electrical inputs should be sealed.
Gaps where the external wall meets a floor should be sealed/taped aswell as sealing the top/bottom of skirting boards.
Space around any pipework/penetrations leading into the building should be sealed.
Seal downlights to air barrier with covers.
Seal around attic hatch.
Replace damaged or missing attic hatch seals.
Seal/tape all vertical & horizontal junctions which form part of an air barrier.
Tape membranes.
All fixtures and fittings should be in place and sealed where necessary.
Seal around access doors/internal garage door frames.
Replace damaged or missing access doors/internal garage door seals.
Waste pipes behind boxing in should be sealed - not forgotten.
Sink/shower/bath wastes should be full of water.
Toilets should be full of water.
Dot and dab plasterboard should have a continuous band of adhesive at top/bottom/corners aswell as around penetrations/switches and sockets.
Electrical back boxes painted/dipped before instalation with airtight paint.
Conduit/cable from electrical back boxes sealed.
Use of tapes at junctions/change of materials which form part of the air barrier.
Seal around electricity meter box and incoming meter tails.
Extractor fans should be one way with shut off dampers.
Allowance should be made for movement/shrinkage within the building when applying seals/tapes to ensure the longevity of the air barrier.

We want your building to pass - If needed we can provide consultation and on-site training for your contractor about reducing air permeability rates in problem areas.

However, if your building does fail, we offer a number of services to ensure that the process is ultimately a success. We will give you full feedback and suggestions to help you make changes which will ensure a pass during the second test, The retest can usually be completed on the same day if the reason for non compliance is fixed within 1 hour.

Smoke testing -

During a smoke test, we will fill the building with smoke and pressurise the space. This will provide a visible indication of the problem areas, as the smoke will flow through the openings. In less extreme situations, we can use devices known as ‘smoke pencils’ to complete the task.

Depressurisation -

Depressurisation is conducted by depressurising the whole building, causing air to enter in through any gaps or cracks. When we reduce the pressure inside, there will be draughts as the air comes back into the building, indicating where the conditioned air is escaping.