Frequently asked questions in relation to Air Leakage Testing 

Air Leakage Testing Of Dwellings what does it need to achieve?

The Design Air Permeability for each dwelling type within a development will be determined by designers as part of the overall DER (Dwelling CO2 Emissions Rate) calculation. The maximum design air permeability allowable (is 10 m3/(m2.hr) @50Pa. 

What and how many dwellings need an Air Leakage Test ?

Sample testing is required of each dwelling type on each development. Building Control will identify the (early) units to be tested. The sample size depends on whether ‘Robust Details’ have been used:  If Robust Details adopted, test one of each dwelling type on each development. If any fail, do remedial work, test again plus another dwelling of the same type on same development  

4 or less dwelling types -            test one of each         

Between 5 and 40 types -             test two of each                   

Above 40 types -                          test 5% of each. For each type, this can reduce to 2% if the first 5 tests are successful. 

Air Permeability explained ?

The air-tightness of a building is known as its 'air permeability' or leakage rate. Air leakage can occur through gaps, holes or cracks in the fabric of the building envelope which are not necessarily visible to the naked eye. This air leakage affects the building's performance and is now firmly enshrined in Part L of The Building Regulations - conservation of fuel and power. Air tightness testing and air permeability testing will highlight any problems with air leakage so they can be remedied. 

What is air leakage in buildings?

Air leakage (also known as air permeability or air infiltration) is the air tightness of a dwelling through uncontrolled means such as cracks and gaps in the building envelope. Any ventilation system installed in a building is seen as a source of controlled air flow and is therefore not considered as air leakage. At a very basic level, air leakage may be seen as unwanted draughts. 

Why is it important to build air tight dwellings?

The energy that we use to heat our homes is primarily created by burning fossil fuels that produces carbon dioxide. If we reduce the air leakage of a building we also reduce the amount of energy required to maintain comfort levels and in turn reduce carbon dioxide emissions. In 2002 the government released a White Paper with a target to reduce carbon dioxide emissions by 20% from 1990 levels by 2010. To achieve these targets, Building Regulations were revised. 

When are air tightness tests carried out?

Air tightness tests are usually carried out during the construction and commissioning process of a building when the external envelope is fully complete, with windows and external doors in place. A full list to determine the readiness of dwelling to be tested can be provided on request. 

Who is approved to carry out air pressure testing?

Air pressure testing may be carried out by a competent person. The British Institute of Non-Destructive Testing (BiNDT) runs a registration scheme of competent persons to ensure adherence to procedures, quality of service and UKAS calibration of equipment. Approved Document Part L1A states that a local authority is authorized to accept a certificate from a person who is registered by The British Institute of Non Destructive Testing. Air pressure testing procedures can also be accredited by UKAS. 

What happens if a dwelling fails air pressure testing?

Guidance in Approved Document Part L1A advises that failed dwelling types will require remedial work and retesting, along with one additional test on the same dwelling type. In the event of a failed air pressure test, Site Measurement Services Ltd can provide a smoke test and advice to help identify the areas of leakage and give guidance on improving the air tightness performance. 

How long is a Certificate valid for?

A Certificate, in theory, is valid until changes to the structure have taken place, i.e. modifications or extensions added. 

Who needs an Air Test.?

All newly constructed dwelling will require an air in accordance with L1A Building regulations. The number of dwellings that need to be tested is dependent on the size of the development. 

How many properties need testing on a development?

"Number of dwelling type  Number of tests to be carried out per dwelling type3 or less      one test of each dwelling type4 to 40      two tests of each dwelling type40 or more  At least 5% of the dwelling type, unless the first 5 units of the tested type achieve the design air permeability, then the frequency can be subsequently reduced to 2%. 

What constitutes a different dwelling type?

"o Detached   o Semi detached o End-terrace  o Mid-terrace o Ground-floor flat    o Mid-floor flat    o Top-floor flat" 

Bindt Certificates must be produced by an accredited tester, who can survey on his behalf?

A team of people can work on gathering the information for the air permeability test as long as they are working under the direction of an Accredited Air Tester. The Accredited air tester must ensure that anyone visiting a property or gathering information on their behalf is both 'fit and proper' (for domestic properties this will include a CRB check) and suitably qualified to gather the information. Only Accredited Air Tester can produce and lodge a Bindt Certificate.   

If I am assessing similar and representative units, can I re-use the data?

If one unit in a block was surveyed in detail the assessor can copy the data model to prepare an air test for another. The assessor needs to be satisfied that they are the same (or make any adjustments as required) and then submit the data to produce an air test for the second unit.  

Who can complete an Air test and produce a Bindt Certificate ?

These can only be completed by a licensed and Bindt accredited air tester and a Bindt tester would only be qualified to test non commercial structures. 

Will air test Certificates be required for rented accommodation?

Yes. The building regulations require air test on any newly constructed dwelling when they are constructed, sold or rented. 

How long will it take to perform an Air test?

The time taken to perform an air test will vary according to the size and nature of the property. It is predicted that it will take between 1- 1.5 hours. Because of the wide variation of commercial buildings, any form of 'average time' would not be meaningful. and these can not be tested by a BINDT qualified tester. 

Is an Air Test required for the private sale of a home between two individuals?

Yes. If the property is newly constructed then the building regulations still apply. 

Does a commercial Property need an Air Test?

Yes an air test must be carried out in accordance with building regulations L2A, but this can not be undertaken by a Bindt accredited tester, it will require a ATTMA qualified tester. 

Are air test required for the EPC i.e. SAP RDSAP or SBEM?

Each dwelling should have an EPC. If an air test has been specified within the design , then the test must be conducted and the result must equal or better the design parameters. Failure to do achieve the design target will result in the building not being passed by the Building Control. 

What happens if I do not conduct and air test?

In most cases building control will not sign off the building, where sign off is provided i.e. in the case of Self build Plots and default value will be used for the EPC. 

On Sale or Rent at what point is the air test required?

the air test will be required for the building control sign off and therefore will not be able to be sold or rented until this have been completed  to the satisfaction of the building control in accordance with L1A building regulations 

On modification at what point is the air test required?

On modification: The person undertaking the work is responsible for providing the Bindt Certificate to the building control. They must then notify Building Control, who will not issue the Certificate of Completion until this is provided. 

Who is responsible for obtaining a Bindt Certificate?

For buildings that are to be sold, the building's owner will be responsible for ensuring a certificate is available; this should be shown, on request, to any prospective purchaser, and should in any case be provided by the owner to the ultimate purchaser before a contract for sale is made. 

How much will Certificates cost?

The price of a certificate will be set by the market and not by Government. We expect these costs to vary according to the size, type and location of the property.  For other buildings, the cost will clearly depend on the size and complexity of the building. 

What is the maximum acceptable level for air test?

The maximum level of air permeability on developments with more than two dwellings is 10 m³/m².h at 50Pa