Part L Air Leakage Testing of Buildings

Air Testing UK provide accredited air testing to complement our energy assessment – SAP, SBEM and Dynamic Thermal Modelling services.

If your building exceeds a certain size, or is a domestic property, you can't hand it over to the client without a valid air leakage test certificate. The air-tightness of a building is known as its 'air permeability' or leakage rate. Air leakage can occur through gaps, holes and cracks in the fabric of the building envelope (service penetrations, wall/roof junctions etc), which are not always visible.

Part L of the Buildings Regulations requires that all non domestic buildings which have a gross floor area greater than 500m2, be subject to mandatory air permeability tests. For domestic dwellings a representative sample of houses (in a development) must be tested.

The air leakage affects the building's performance and is one of the key areas in meeting Building Regulations Part L or exceeding these standards for low carbon buildings, Code for Sustainable Homes and BREEAM. Making a building air tight reduces the amount of fuel needed to heat it, which in turn reduces the CO2 produced, reduces your carbon footprint and your energy bills.

The air tightness strategy should be developed in line with the fabric and ventilation proposals. We are experienced in delivering air leakage rates of less than 3m3/(h.m2), which is a requirement on many Code 4, 5 and 6 dwellings.

Air Testing UK provide BindT accredited air testing services which form part of the requirement for SAP and SBEM As Built Certification. Air permeability testing is a mandatory requirement under Building Regulations Part L for all new houses and large extensions (25%+ of existing). The air permeability rate that a dwelling requires is determined by the SAP evaluation but should be less than 10a/c at 50pa. In most cases, it is becoming more common for air leakage rates of less than 5 a/c at 50pa as Building Regulations becomes more stringent.

2010 Regulations

An air test is not required for every dwelling on a site; a pressure test is required on three units of each dwelling type or 50% of the instances of the dwelling type whichever is fewer.

A confidence factor will apply to dwellings not pressure tested. Where a dwelling has been pressure tested, this value is used in the SAP DER calculation.

Where the dwelling has not been pressure tested, the value used in the SAP DER calculation is the average of the measured values for this dwelling type, but with the addition of a confidence factor of 2m3/(h.m2) at 50Pa.

This means that for building regulations a design air permeability of 8.0 is the maximum in order to meet the maximum of 10 at completion stage, and for Code 3 or 4 schemes the air leakage rate will typically need to be significantly better than this (3 and below).

Air Leakage Testing when it suits you

Air Testing UK will fit in the test around you, give advice on how to prepare, provide advice on how to pass and provide feedback directly after the tests have been completed.

Air Testing UK have been in business for 20 years, specialising in low energy/emission buildings. Our experience extends to PassivHaus design, Thermal bridging and modelling, Code and BREEAM assessments, which complement the air testing services. We understand the principles and our technical capability provides a complete service.

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