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.
The heat losses of the building are reduced so much that it hardly needs any heating at all. Passive heat sources like the sun, human occupants, household appliances and the heat from the extract air cover a large part of the heating demand. The remaining heat can be provided by the supply air if the maximum heating load is less than 10W per square metre of living space. If such supply-air heating suffices as the only heat source, we call the building a Passive House.
Univ. Prof. Dr Wolfgang Feist Head of Energy Efficient Construction/ Building Physics at the University of Innsbruck, Austria and Director of the Passive House Institute, Darmstadt, Germany.
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)
EnerPHit Standard for refurbishments
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.
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
Claiming the Passivhaus Standard in the UK:
The Passivhaus Trust recommends that the best way to achieve quality assurance for a Passivhaus project is through certification by a registered Passivhaus Certifier. It is reasonable to claim that a building is a non-certified Passivhaus provided that it still meets the requirements of the standard. Read more about this in our Technical briefing paper here.
images courtesy: Simmonds Mills/ Thermal Inspections Ltd
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%.
image courtesy: www.passipedia.org
The Passivhaus Institute has developed a series of certification processes to ensure the quality of any official Passivhaus buildings and practitioners:
- The Passivhaus Planning Package (PHPP), used to inform the design process and to assess or verify compliance with the Passivhaus Standard.
- Certification for designers who have the expertise to deliver Passivhaus buildings.
- A certification process for Passivhaus buildings, which applies both to the proposed design and the completed building.
A number of UK organisations have been approved to assess and issue the Quality Assured Passivhaus Certificate. Details of Passivhaus Trust members, partners and staff who can provide certification can be found here.
images courtesy: Dr Jon Hand, University of Strathclyde