Air tightness is an essential part of a refurbishment or new build.

The Passivhaus standard requires a maximum figure of 0.6 air changes per hour, or 1.0 ach for refurbishment to the EnerPHit standard.

This table shows figures achieved on recent projects that we have been involved with to some extent.  It shows that the method of construction has little influence on the final result; but contractors with most experience do best.