Tougher airtightness targets and more testing are more likely to be required when revisions to Part L of the Building Regulations come into force in October, according to Chiltern Dynamics.

“If the 25% improvement in the overall emission rating is to be met, airtightness performance itself will have to improve,” said head of energy services Tom Gregory.

“Although a target air permeability of 10m³ (h.m²) at a pressure difference of 50Pa is still acceptable under the new Part L, the specific test requirement will often be significantly lower to achieve the overall Target Emission Rate based on SAP or SBEM calculations.”

Mr Gregory said more developments would need testing and a much higher proportion of dwellings would be tested on any development.

“Under the 2010 revision, three tests or 50% of each dwelling type must be tested compared with one or two tests currently.”