With a growing demand for buildings to be more energy and carbon efficient, buildings are often being built to either “Passivhaus” or “AECB Standard” (formerly known as Silver Standard).

UK Passivhaus is based on the German Passivhaus Standard and has a target and calculation method which is different from Building Regulations Air Permeability. BAT have been undertaking Passivhaus testing for a number of years and have ATTMA Certified Passivhaus Testers. Air Tightness is a primary characteristic of a Passivhaus build, as a continuous air tight outer shell will prevent heat losses from the building.

The domestic Passivhaus target is 0.6 m³/hr.m³ (otherwise known as air changes per hour) and is based on the building occupied volume. Strict rules apply to the calculation of the occupied volume and it is recommended that this calculation be carried out by the Passivhaus Assessor from the building model. It is common for three Air Tests to be undertaken, one at each of the following stages. Stage 1 – Once the initial air barrier sealing has been completed. Stage 2 – Once the secondary fix works have been completed. Stage 3 – At building completion.

The AECB Standard has a higher maximum leakage of 1.5 m³/hr.m³ with Mechanical Ventilation with Heat Recovery and 3.0 m³/hr.m³ with Mechanical Extract Ventilation.