What is a Passivhaus (or Passive House)?
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.
What is the Passivhaus standard
The definition of Passivhaus is driven by air quality and comfort: “A Passivhaus is a building in which thermal comfort can be achieved solely by post-heating or post-cooling the fresh air flow required for a good indoor air quality, without the need for additional recirculation of air.” – Passivhaus Institut (PHI)
How to achieve the Passivhaus Standard in the UK
To achieve the Passivhaus Standard in the UK typically involves:
- very high levels of insulation
- extremely high performance windows with insulated frames
- airtight building fabric
- ‘thermal bridge free’ construction
- a mechanical ventilation system with highly efficient heat recovery
- accurate design using the Passive House Planning Package (PHPP)
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%.