AIRTIGHTNESS REGULATIONS
Air permeability and air pressure testing
The DER is calculated using the design air permeability specified by the designer. Where testing is required to demonstrate that the design air permeability has been achieved the dwelling shall be air pressure tested in accordance with the Air Tightness Testing and Measurement Association (ATTMA) publication “Measuring Air Permeability of Building Envelopes”. The manner approved for recording the results and the data on which they are based is given in section 4 of that document. The tests shall be carried out by a suitably qualified person such as a tester who is registered with or approved by the British Institute of Non-destructive Testing in respect of pressure testing for the air tightness of buildings.
A block of flats shall be treated as a separate development irrespective of
the number of blocks of flats on the site.
Most larger developments will include many types of unit including terraced
(end and centre), semi-detached, flats, etc. and at least one of each type
shall be tested to confirm the robustness of the designs and the construction procedures.
Dwellings built to accredited construction details
On each development built to accredited construction details an air pressure test shall be carried out on a unit of each dwelling type selected by the district council.
Dwellings NOT built to accredited construction details
Air pressure tests shall be carried out on each dwelling type not built to accredited construction details in the development to the number given in the table below. The dwellings selected for test shall be chosen by the district council in consultation with the builder. They shall be selected so that about half of the tests on each dwelling type are carried out during the construction of the first 25% of the dwellings of that type.
Demonstrating compliance
Compliance with the air permeability requirements shall be demonstrated
where –
(a) the measured air permeability is not greater than 10 m3/(h.m2) @ 50 Pa; and
(b) the DER on completion, calculated using the measured air permeability, is equal to or less than the TER.
Number of dwellings of the dwelling
type
|
Number of dwellings tested of the
dwelling type
|
| 4 or less |
One
|
| More than 4 but not more than 40 |
Two
|
More than 40
|
At least 5% of the dwelling type unless the
first 5 dwellings of that type achieve the
design air permeability in which case the
testing frequency may be reduced to 2%
|
Consequences of failing a pressure test
Where a dwelling fails to achieve its design air permeability, remedial measures shall be carried out, such that on retest the design air permeability is achieved. However, in the period up to 31 October 2007, if the initial test result on a dwelling is unsatisfactory, provision shall be made to –
(a) carry out remedial measures such that on re-test a result is achieved that shows either –
(i) an improvement of 75% on the difference between the initial test result and the design air permeability; or
(ii) if more easily achieved, a test result within 15% of the design air permeability; or
(b) revise the TER by substituting the measured air permeability for the value given in Appendix R of SAP and demonstrate that the DER for the building as built is equal to or less than the revised TER.
In addition to the remedial work on the dwelling that failed to achieve its design air permeability, one additional dwelling of the same type shall be tested to increase the overall sample size. | 
