By now, you may be familiar with the general concepts of what makes a Passivhaus or Passive House. A high quality home which prioritises the comfort and wellbeing of it’s occupants through superior air quality, and which is energy efficient with cheaper running costs. In order for a home to become certified, it must be designed and built to the Passivhaus standard. In this article we take a brief look at what that means, and how a home can become a certified Passive House.
In the UK, Passivhaus Standard generally 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
The Passive House Institute (PHI) in Darmstadt, Germany, developed the Passivhaus standard based upon rigorous scientific research and testing. One of the original drivers for developing the Passivhaus standard was to close the large gap between how buildings were designed to perform and how they actually perform once occupied.
In the UK, there are occasionally claims that buildings meet or exceed the Passivhaus standard simply because they might meet one or more of the requirements. Other claims can be that buildings are designed using “Passivhaus principles,” a term not endorsed by the Passivhaus Trust as the building does not meet all of the quality assurance requirements. A building may not be described as a Passivhaus unless it has been modelled using the PHPP and meets ALL of the requirements of the Passivhaus standard. The PHI established a process to certify buildings meet the Passivhaus standard, and PHI publishes quality assurance criteria.
There are a series of quality assurance requirements to be met in order to certify that a building is a Passivhaus/meets the Passivhaus standard, including the use of the PHPP, pressure tests taken to the required standard and photographic records of the project, to name a few.
On occasion, buildings may come very close, but fail to meet one or more criteria, for example, peak load or airtightness targets. In this instance, the PHI Low Energy Building standard can be awarded. It is not, however, the intention that projects should start out aiming for this standard.
To achieve certification, all Passivhaus projects must be signed off by an independent accredited Passive House certifier who ensures that all of the quality assurance requirements have been met. These organisations must be separate to the main design team and provide impartial verification that all Passivhaus criteria have been satisfied.
What are the advantages of getting a building certified?
- Certainty that the agreed upon energy standard will actually be achieved.
- Increase in property value through the independent quality assessment.
- The reviewed energy balance using the PHPP can be submitted for various subsidy programs.
- The certifier can spot energy saving measures which would be too costly and go above and beyond what is required for the Passivhaus standard. This can save unnecessary construction costs.
An overview of the certification procedure:
- Initial check – at the start of the project – The certifier will check whether the project contains special aspects and will clarify how these should be assessed in the building certification.
- Preliminary review – design phase – Assessment of the concepts for the design, insulation and building services, and of the preliminary version of the PHPP calculation for consistency with the certification criteria.
- Design stage review – before the start of construction work – All energy-relevant planning documents, the technical data of the construction products and the complete PHPP calculation should be submitted to the certifier preferably before the start of the construction work. After a careful review and comparison with the energy balance calculation, the certifier will inform the client of any necessary corrections. If all is well, the certifier will confirm that the envisaged energy standard will be achieved with the implementation of the planning at hand. Execution of the construction work can now begin
- Queries regarding certification – continually during planning and construction – For planning decisions which affect the energy balance, it may make sense to coordinate with the certifier at an early stage how these decisions will be assessed in the context of certification if the Passivhaus designer is uncertain.
- Final review – after completion of the construction work – After completion of the construction work, any changes to the planning will be updated in the final review and proof from the execution of construction work (e.g. airtightness test, documentation of flow rate adjustment of the ventilation system, construction manager’s declaration) will be checked.
If all criteria have been fulfilled, the building owner will receive a certificate, a supplementary booklet with documentation of the energy balance calculation and all relevant characteristic values of the building, and an optional wall plaque. The authenticity of the certificate will be confirmed by an identification number that will be specially issued to the certifier by the PHI.
How much does it cost?
There are no centrally fixed prices for certification. Each certifier calculates their offer so that the expected expenses for meticulous checking of the respective building are covered. In addition, a modest fee is included in this calculation which every certifier pays to the PHI to cover expenses for the on-going support and resources that it provides to all certifiers. One you have chosen your certifier, you can get in touch and ask for a quotation.
At Thinking Buildings we are very lucky to have Rachel, our certified Passivhaus designer. She qualified in 2021 and has been involved in many projects, notably Weedon. She can guide our clients through the entire process of designing a home the the Passivhaus standard.
We have many other low energy homes on our website and much more information about Passivhaus on our website here. If you would like to contact Rachel about turning your Passivhaus dream into reality, do get in touch here, she will be pleased to talk to you.
Information gathered from the Passivhaus Trust Website.
Further reading:
Building Certification Guide
Claiming the Passivhaus Standard
