A Passivhaus is a super-insulated, virtually air-tight building that is primarily heated by solar gain and by internal gains (e.g. people, electrical equipment, etc...). It also minimises energy losses by eliminating thermal bridging and using a MVHR which can save up to 90% on space heating costs.

To begin it is crucial to understand that there is a huge difference between a 'Passive House' and a 'Passivhaus'.

A Passive House is simply a house built using the principles of passive design - it is not certified by the Passivhaus Institut. In comparison, a Passivhaus has a stringent standard to abide by. To receive this certification it must achieve the following performance characteristics:

• Total energy demand for space heating and cooling must be less than 15 kWh/m² per year.
• Total energy demand for appliances, hot water, and space heating and cooling must not exceed 120 kWh/m² per year.
• Exterior Insulation must have a U value of less than 15 W/m²K per year.
• Windows must not exceed 0.80 W/m²K
• Airtightness must be less than 0.6 air changes per hour when subject to a force of 50Pa.
• Ventilation must ensure over 80% heat recovery from ventilation exhaust air.