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What Is Passivhaus?

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 Passivhaus Standard

The new-build Passivhaus Standard requires:

  • a maximum space heating and cooling demand of less than 15 kWh/m2.year or a maximum heating and cooling load of 10W/m2
  • a maximum total primary energy demand of 120 kWh/m2/year
  • an air change rate of no more than 0.6 air changes per hour @ 50 Pa

 

The Passivhaus refurbishment standard, EnerPHit, requires:

  • a maximum space heating and cooling demand of less than 25 kWh/m2.year or a maximum heating and cooling load of 10W/m2
  • a maximum total primary energy demand of 120 kWh/m2/year + heat load factor
  • an air change rate of no more than 1.0 air changes per hour @ 50 Pa


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

 

Why 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 Europe

image courtesy: www.passipedia.org

 

Certification

The Passivhaus Institute has developed a series of certification processes to ensure the quality of any official Passivhaus buildings and practitioners:

  1. The Passivhaus Planning Package (PHPP), used to inform the design process and to assess or verify compliance with the Passivhaus Standard.
  2. Certification for designers who have the expertise to deliver Passivhaus buildings.
  3. 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

 

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