Introduction by Paul McNally Architect

The following advice comes from Paul Overy, of Overy Associates in Clonmel, Co. Tipperary with whom I have collaborated on several low energy and passive projects. Overy Associates provide expert Building Services Consultant services.

Assigned Certifier, Part L, and Air permeability pressure tests in non-domestic buildings

This email gives our view on the above subject matter.  Assigned Certifiers need to be careful what test results are accepted for air tightness testing. Potentially a new building could fail Part L under the CPC and EPC rules.

There is no requirement of air permeability pressure testing in Part L for non-domestic buildings.  Notwithstanding this, when a BER is prepared for a non-domestic building, the test results are only acceptable if carried out by a certified person.

SEAI’s BER section insist that individuals carrying out the tests demonstrate their competence by being registered under NSAI’s Air Tightness Testers Scheme or by being accredited to carry out tests by INAB or another body capable of providing accreditation to ISO 17025.  It is not acceptable for the tester to self certify that they follow the standards.  That eliminates some air tightness testing companies.

The list of testers on NSAI’s website can be found here.


If you get a building air tightness tested by an unregistered person, the BER assessor cannot use the results to generate the BER and will have to use a default air permeability of 25 m3/h2/m2 at 50Pa in the BER model, where the building perhaps may obtain a result below 5 m3/h2/m2 at 50Pa.

This could :

  • Degrade the BER rating somewhat.
  • Potentially make a building which would just pass Part L, fail Part L requirements under CPC and EPC rules.  A rating in the A or upper B range is unlikely to fail in these circumstances, but a lower rating building might fail.

When the new non-domestic Part L comes out, the above will be all the more important.

Formal BER certificates are required to be produced when new buildings are completed.  BER assessors are required by SEAI’s Code of Conduct to inform clients if a new building fails Part L.

but a lower rating building