What is Passivhaus?

Buildings are a significant culprit of carbon emissions – accountable for 35% of total global energy consumption. Backed with over 30 years of international evidence, Passivhaus is a tried & tested solution that gives us a range of proven approaches to deliver net-zero-ready new and existing buildings optimised for a decarbonised grid and augmented for occupant health and wellbeing. Passivhaus buildings provide a high level of occupant comfort using very little energy for heating and cooling.

Passivhaus adopts a whole-building approach with clear, measured targets, focused on high-quality construction, certified through an exacting quality assurance process. For more on why adopting an efficient first approach is cruicial to meeting carbon targets, check here.

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.

What is the Passivhaus standard?

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Why Passivhaus?

It is important to understand the value & sound business case for building to the Passivhaus Standard; it is so much more than just world-leading energy efficiency and thermal performance. There are several benefits, and many are interconnected – creating a catalyst for positive effects. Low energy bills, constant fresh air, superior internal comfort, peaceful and quiet interiors - the list goes on. Learn why the Passivhaus approach is good for people and the planet. Get more detail in our Passivhaus benefits guide.

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 Passivhaus.

Prof. Dr Wolfgang Feist Director of the Passive House Institute, Darmstadt, Germany

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How to achieve the Passivhaus Standard in the UK

To achieve the Passivhaus Standard in the UK typically involves:

accurate design modelling using the Passive House Planning Package (PHPP)

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

Performance targets for a European climate


	Passivhaus		EnerPHit
Airtightness n50	≤ 0.6 ACH @ 50 Pa		≤ 1 ACH @ 50 Pa
Space Heating Demand (SHD)	≤ 15 kWh/m².a	-	≤ 25 kWh/m².a (variable)*
Peak heating load (alternative criterion)	-	≤ 10 W/m²	-
Primary Energy Renewable (PER)	≤ 60 kWh/m².a		≤ 60 kWh/m².a (variable)*
Space cooling demand	≤ 15 kWh/m².a		≤ 25 kWh/m². yr
Surface temperature	≥ 17 °C		≥ 17 °C
Overheating	Max 10% > 25°C		Max 10% > 25°C

*For EnerPHit, the heating demand target varies according to climate zone, of which the UK spans three, most falling into 25 kWh/m².a. PER varies by building use, and, in retrofit, by allowance for larger heating and cooling demand compared to a new build.

The table above shows headline criteria for Passivhaus new build and retrofit. Readers must refer to the full criteria to ensure they have the correct values for their specific project – variations may apply. More information and detailed criteria on the different Passivhaus classes, Classic, Plus, & Premium, can be found here.

All Passivhaus projects must use the design tool Passive House Planning Package (PHPP.)

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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 self-declared Passivhaus provided that it still satisfies all the requirements of the standard. Read more about this in our technical briefing paper 'Claiming the Passivhaus standard'.

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Certification

Over thirty years of experience demonstrates that the high levels of comfort and energy savings associated with the Passivhaus Standard is achieved through independent quality testing. All certified Passivhaus buildings undergo a rigorous compliance process. Certification is also available for specific components, Designers/ Consultants & Tradespeople.

Building Certifiers: A number of UK organisations have been approved to assess and issue the quality assured Passivhaus Certificate. These organisations must be separate to the main design team and provide impartial verification that all Passivhaus criteria has been satisfied. Details of who can provide Passivhaus certification can be found here.

Simplified PHPP workflow to Certification:

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