Latest Air Tightness Testing Regime

ADL1A 2010 now provide more defined terms of ‘dwelling type’. To qualify dwellings to be considered as the same ‘dwelling type’, they must have the:

  • Same standard form - i.e. detached, semi- detached, ground floor flat
  • Same number of storeys
  • Same design Air Permeability Rate (APR)
  • Similar adjacency to unheated spaces e.g. stairwells or integral garages
  • Same principal construction details whether Accredited Construction Designs (ACDs) or bespoke
  • Same number of significant penetrations (+/- 1) - i.e. windows, doors, flues/chimneys, supply/exhaust terminals and waste water pipes
  • Envelope areas that do not differ by more than 10%
  • In addition for dwellings, if air test results are to be re-used in SAP calculations for untested plots of the same dwelling type, a 'confidence' factor needs to be applied which means that the test results must be 2m³/(h.m²) at 50Pa better than the design air permeability allowed in the SAP calculation.
  • In other words, if the target air permeability for the dwelling type in SAP is 6, the tested plot would need to achieve 4, for the result to be re-used in untested plots.
  • Building Control will still have final say but the testing regime can usually be negotiated between the BC officer and air tester. 

(ADL1A – Available for Wales from here and England from here)

Need more guidance on the information above call (landline) 01792 424569; (mobile) 07986 099438 or email [email protected]

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