The Passivhaus Standard

Passivhaus defines very-high performance standards for building elements and airtightness that deliver new buildings that are extremely energy efficient and have high levels of thermal comfort without the need for traditional heating systems.

Crossway Passivhaus home
The Crossway eco-arch Passivhaus was featured on Grand Designs and utilised SmartHTC thermal performance technology to verify its true energy performance

What is Passivhaus?

Passivhaus is a high-specification energy performance standard for both domestic and non-domestic buildings. A Passivhaus designed building needs to be super-insulated, have very high-performance windows/doors and be extremely airtight. The end result is a space heating demand so low that there is no requirement for a conventional heating system.

Passivhaus is a tried and tested standard that applies to new-build buildings only and has to date certified over 65,000 buildings worldwide. A slightly relaxed standard, known as EnerPHit, applies to retrofit projects where the existing architecture and potential conservation issues mean achieving the Passivhaus standard is unfeasible.

The Passivhaus standard adopts a holistic whole-building design approach alongside a formal certification process that is designed to be achieved without relying on renewables. Specific guidelines are provided for minimum efficiency levels of building elements, infiltration, heat recovery and thermal bridging.

Each certified Passivhaus goes through a quality assurance process which includes a detailed review of the design, construction and on-site installation. This ensures that the exacting levels of thermal performance are met alongside high-quality workmanship.

How is Passivhaus achieved?

A Passivhaus building will typically deliver 70% less heating requirement than Part L building regulations. It can achieve this through:

  • Energy-efficient built form and orientation
  • Continuous insulated fabric with no thermal bridging
  • Very high-performance windows and glazing
  • Airtight building envelope with minimal infiltration
  • Mechanical ventilation with heat recovery (MVHR)
  • Use of solar shading to avoid overheating

In European climates, the space heating load must be below 15 kWh/m2 of usable internal floor area, known as Treated Floor Area (TFA). In addition, the total primary energy demand of the building must be less than 120 kWh/m2. The heating demand can solely be met using a heating element within the MVHR system to maintain a good indoor air quality – without a need for re-circulated air.

In the UK, the Passivhaus target U-values of building elements and ventilation requirements are:

  • Opaque building elements (e.g. walls, floors, roofs) <= 0.15 W/m2K
  • Windows/doors <= 0.8 W/m2K or <= 0.85 W/m2K once installed
  • Thermal bridging <= 0.01 W/m2K
  • Fan efficiency <= 0.45 W/m3h
  • Heat recovery >= 75%

Part L vs Passivhaus U-values

The diagram below highlights the differences in U-values of building elements (measured in W/m2K) between a typical Part L compliant new-build house and the Passivhaus (PH) standard.

Part L vs Passivhaus U-values

Measuring Passivhaus targets

Our unique products are ideally positioned for measuring the thermal performance, infiltration and U-value targets set in the Passivhaus standard.

Pulse air receiver, controller and compressor

Pulse Air Permeability Testing

A pioneering approach to fabric air permeability measurement that releases a low-pressure pulse of air for realistic and accurate measurement of airtightness of buildings in seconds.

Learn more about Pulse Air Permeability Testing
Temperature sensors

SmartHTC Measured Thermal Performance

A low-cost and non-invasive way of measuring the true thermal performance of a house. It requires temperature and meter data to calculate an accurate heat loss rating over a 3-week period.

Learn more about SmartHTC Measured Thermal Performance

Measuring airtightness in Passivhaus buildings

Our Pulse air permeability measurement system has been specifically tested in very airtight dwellings, such as Passivhaus new builds and EnerPHit retrofits. It has been proven to measure very airtight dwellings just as reliably as the incumbent blower door fan technique without additional equipment.

Using the blower door fan method in Passivhaus properties normally requires a specialist low-flow fan, window mounted in a fixed panel and fully sealed, with a much greater number of readings taken across both pressurisation and depressurisation in order to keep measurement uncertainty to a minimum.

Pulse air leakage testing in very airtight Passivhaus properties

Determining the thermal performance of Passivhaus buildings

Constructed in 2008 and featured on Grand Designs, Crossway was one of the first Passivhaus certified buildings in the UK. Our unique SmartHTC thermal performance test was used to measure the Heat Transfer Coefficient of Crossway using real measurements of temperature and energy consumption.

SmartHTC demonstrated that the energy-efficient ambitions of the Passivhaus design were still being realised twelve years after construction. The measured performance was very similar to the predicted performance at the design stage by the Passivhaus Planning Package (PHPP).

SmartHTC monitoring of Passivhaus buildings

Measuring U-values of Passivhaus buildings

Although manufacturers always provide U-values of windows, doors and pre-fabricated panels such as Structural Insulated Panels (SIPs), it is always beneficial to measure the in-situ U-values once installed.

Our in-situ U-value measurement system is uniquely positioned to measure in-situ U-values of Passivhaus buildings using heat flux plates. The heat flux plates are capable of measuring the low U-values required by the standard and will provide a measured U-value that conforms to the ISO 9869 Standard.

In-situ U-value measurement of Passivhaus building elements