What is Passivhaus?
Passivhaus explained in 90 Seconds
Passivhaus buildings provide a high level of occupant comfort while using very little energy for heating and cooling. They are built with meticulous attention to detail and rigorous design and construction according to principles developed by the Passivhaus Institute in Germany, and can be certified through an exacting quality assurance process (Passivhaus Trust).
The basic principle of a Passivhaus is to reduce the heat losses of a building to the point that it hardly needs any heating at all. The sun, occupants, household applicants and the warmth from extracted air cover most of the heating demand. The standard relies on good levels of insulation with minimal thermal bridges and well-designed uses of solar and internal gains.
The buildings are made as airtight as possible which results in the installation of mechanical ventilation heat recovery (MVHR) systems which provide excellent air quality and heat recovery efficiencies in excess of 80%. All of this means that a traditional heating system is no longer required and the shortfall can be covered with a small unit, such as a wood burning stove.
Despite the name, its not just houses that can be Passivhaus certified, there are a growing number of non-domestic Passivhaus buildings in the UK, particularly schools.
Passivhaus certification is also possible for very low energy retrofit projects. EnerPHit is a slightly relaxed standard for retrofit projects, where the existing architecture and conservation issues mean that meeting the Passivhaus standard is not feasible.
Why Choose Passivhaus?
Passivhaus buildings achieve a 75% reduction in space heating requirements, compared to standard practice for UK new build. The Passivhaus standard therefore gives a robust method to help the industry achieve the 80% carbon reductions that are set as a legislative target for the UK Government. Passivhaus also applies to retrofit projects, achieving similar savings in space heating requirements.
Evidence and feedback to date shows that Passivhaus buildings are performing to standard, which is crucial, given that the discrepancy between design aspiration and as-built performance for many new buildings in the UK can be as much as 50-100%. (Passivhaus Trust).