By building a tighter property, building standards will improve, giving the client a better end product, and the property's running costs and efficiency will improve. 

The better the final air tightness test result, the better the energy calculation, which in turn means the final EPC (Energy Performance Certificate) will have a higher rating. 

Not only will your EPC have a higher rating, but your building will also run more efficiently, your heating and lighting costs should be less, and the energy efficiency will be better. 

Air tightness testing is a mandatory requirement of Part L of the building regulations for a new build property, whether residential or commercial. All new build buildings must be tested.  

The air tightness test of a building is guided by a set target within the energy calculation (SAP or SBEM). The overall calculation determines the target figure. The better the air test result, the less leaky or draughty your property will be. As a minimum, the target figure must be met or bettered to pass the air tightness test. 

You must provide a copy of the air test certificate and EPC to sign off your building upon completion of the build. Once provided, building control can sign off the build. 

The building should be tested as soon as it is complete, as all the final finish has been completed and the best chance of a successful result is possible. Once the property becomes occupied and lived in, the fabric of the building will change.  

The more advanced the build and final finish, the better the result will be. Most leakage points will be sealed, the better the finish, the better the result.