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iATS Air Pressure Testing, Air Leakage Testing
and Air Tightness Testing to ATTMA TS1 / ATTMA TSL1


Blue Tree Acoustics provide certified Air Tightness Testing for domestic buildings.


We offer Independent Airtightness Testing Scheme (iATS) accredited testing for compliance of Approved Document L1A to the Building Regulations (ADL1A)


Air tightness tests are undertaken in accordance with Air Tightness Testing & Measurement Association (ATTMA) TS1 or TSL1 and Thermal performance of buildings - Determination of air permeability of buildings. Fan pressurization method BS EN:13829 (2001)


We provide certification and reports for all tests within 3 days of testing in order for the results to be passed to building control as soon as possible (usually, the results are provided the day after testing).


The report and certificates will provide the measured air permeability value, and will compare this to the selected Design Air Permeability for each dwelling type within a development.


The Design Air Permeability is calculated in the DER (Dwelling CO2 Emissions Rate) evaluation at design stage by the SAP consultant (we can also offer SAP assessments).


The air tightness test simply measures the actual on site performance, and allows comparison with the stated design value.


The maximum design air permeability allowable under the building regulations is
10 m3/(h.m2) @50Pa.


In simple terms, this is a flow of air of 10 m3/hour for every m2 of dwelling envelope area, when the building is subject to a pressure of 50Pa.


The design air permeability may be lower than 10 m3/(h.m2), as a better standard may be required to offset lower performances in other energy performance areas.


From initial specification to on-site testing, our professional and helpful service provides Clients with practical and cost effective solutions to achieve compliance with Part L1A of the Building Regulations.


Each actual air tightness test is a non-destructive test of building air leakage. Designed ventilation is excluded as the test is only concerned with areas of unintentional weakness such as gaps, cracks, incomplete seals.


The number of tests required varies depending on the size of the development and the number of dwelling types e.g. flats, terraced houses, semi-detached, detached etc. Small sites may require only one test. Larger sites may require many more tests.

There are two versions of the building regulations which your site might be subject to which require air tightness testing. The first version came into effect in 2006, the second on 1st October 2010. The version your site falls under is dependant on the date the site was registered.




ADL1 2006
Number of instances of the dwelling type Number of tests to be carried out on the dwelling type
4 or less One test of each dwelling type
Greater than 4, but less than 40 Two tests of each dwelling type
More than 40 At least 5% of the dwelling type, unless the first 5 units of the type that are tested achieve the design air permeability, when the sampling frequency can be subsequently reduced to 2%


Dwelling types are: Detached; Semi-detached; Top floor flat; Mid floor flat; Ground floor flat; End terrace; Mid Terrace.

Also there should be subdivision in types so that there is a difference of no more than 15% in gross floor area between the smallest to largest in the group.

There should also be no more than 1 extra significant opening in the group.


ADL1 2010
Number of instances of the dwelling type Number of tests to be carried out on the dwelling type
6 or less 50% of each dwelling type
Greater than 6 Three tests of each dwelling type


Dwelling types are: Detached; Semi-detached; Top floor flat; Mid floor flat; Ground floor flat; End terrace; Mid Terrace.

Also there should be subdivision in types so each type has the same number of storeys; the same design air permeability; similar adjacency to unheated spaces (stairwells that garages etc); the same principal construction details; have envelope areas that do not differ by more than 10%; and have no more than 1 extra significant penetration (window, door, flue, pipes etc). A block of flats should be treated as a separate development irrespective of the number of blocks on the site.

Where a dwelling has not been tested, the assessed air permeability is the test result from a similar dwelling plus 2 m3/(h.m2) @50Pa. In effect this means that the target for compliance is 8 m3/(h.m2) @50Pa unless all units are tested.


Typically, a site will require between 2 and 10 tests.


Whether your site is one dwelling or a large development, and whether it is located in Liverpool, Manchester, Leeds, Hull, Sheffield, Birmingham, Leicester or Newcastle - we will be able to help.


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Blue Tree Acoustics