Is an airtight seal just an airtight seal?

摘要

The legal requirement to consider airtightness in building designs has been around since the 2006 changes to UK Building Regulations. This is the same for every version of the regulations that apply to all regions of the UK, whether it be England, Scotland, Wales or Northern Ireland. The measurement for calculation air loss out of, or ingress into, a building is measured in cubic metres (mJ), per hour (h), per square metre of building envelope (m1) and at a differential pressure of 50 Pascals (Pa) between internal and external air pressure. The back stop maximum leakage is 10, equivalent to 10m~3 (h.m~2) @50Pa. When designing to Passivhaus standards, this gets a little more complicated as they refer to airtightness as so many changes of air per hour. This relates more to the cubic capacity of the building or room, rather than the surface area of the envelope of the building. Notwithstanding this, to give some comparison it is generally agreed that Passivhaus is looking for a goal of 0.6m3 (h.m2) @50Pa, or less.