Passivhaus is an open-source and free methodology. However, employing the right consultants is key to a successful project.
Passivhaus consultants and qualifications
There are three certified professionals in the Passivhaus Process and Certification process:
Certified European Passivhaus Designer (CEPH): This is a qualification that can be achieved through two pathways:
A course and exam: Online and in-person courses are available throughout the world. The course topics include Passivhaus principles, economics, physics and PHPP (the thermal modelling software used in Passivhaus). The course ends with an exam that, if passed, awards certification. The course is open to anyone. Clients often choose to do the course but not the exam to learn about the standard. CEPH consultants include Architects, Structural Engineers and Services Engineers.
Build a Passivhaus certified building: Passivhaus is an open-source standard. Some clients choose to build a Passivhaus themselves; 'learning on the job'. This could be a great option for individuals with construction experience. However, Passivhaus Certifiers need to provide a lot of support on the way and, as a result, are likely to charge higher fees for certifying buildings without a CEPH.
The Passivhaus Certifier: A certifier is a CEPH with many years experience that has worked on a number of Passivhaus certified buildings. That individual takes additional qualifications with the Passivhaus Institute in Germany to qualify as a Passivhaus Certifier. This qualifies them to award Passivhaus certification to buildings on behalf of the Passivhaus Institute. At the time of writing, there are 8x companies in the UK that have this qualification.
Certified Passivhaus Tradesperson: This is a tradesperson or building contractor that has taken a qualification that is similar to the CEPH but that focuses on the construction of Passivhaus buildings.
The Passivhaus process
The process is as follows:
The CEPH designs, or plays a key role in designing, the building. As Rich is a CEPH, he has the skills needed to design the building with the correct principles in place to meet the standard. The CEPH will oversee the detailed design of the building, assess details to ensure that they meet thermal bridging requirements and carry out on-site inspections. As Architects commonly have an on-site inspection role as part of the building contract, this role can be 'doubled up' with Architects who are also qualified CEPH's; saving fees.
As part of that role, the CEPH also produces evidence that is supplied to the Certifier:
The PHPP model; this is the thermal model that calculates the metrics used to certify the building including the space heating energy consumption, primary energy consumption and predicted days of overheating.
The evidence: the calculations and measurements that underpin the PHPP model. This will include drawings that demonstrate that the inputs into the PHPP model have been measured in accordance with the Passivhaus standard, construction details and specifications.
The Certifier checks and validates the evidence supplied by the CEPH. They also share experience and advice from other projects. Once the evidence is checked, the Certifier will also carry out on-site inspections to check that the details will meet the standard.
Certified Passivhaus Tradespersons construct the building to the details. Passivhaus Tradespersons have the training required to appreciate what the details are trying to achieve. This ensures that the final building follows the construction details correctly and that it is built to the standard required within the design. It is essential that the contractor employed to deliver the building has Passivhaus training and experience as incorrectly built details could fail the standard; costing a lot of time and cost in rectification and repairs.
Additional Passivhaus Roles
Below are a couple of additional roles within the Passivhaus process that need to be considered:
Thermal Bridge Calculations: Building junctions within Passivhaus buildings need to achieve a low level of thermal bridging. Most details can be assessed visually. However, sometimes a detailed analysis of the thermal bridge needs to be carried out. Rich Tyers Studio's carries out in-house 2D thermal bridge calculations and will make an allowance for these within the fee quotation. Very complex details might require a 3D calculation that would require an external consultant to complete. Ideally, we would design the building to avoid the need for any calculations.
MVHR Duct Design: We would usually recommend that a services engineer is appointed. This consultant will design all of the Mechanical, Electrical and Plumbing systems including the MVHR duct design. However, if the client chooses not to do this, a specific MVHR designer will be required to design ductwork.
Passivhaus Process and Certification: Certified Products
It is theoretically possible to design a Passivhaus building with conventional building products. However, some metrics that are required within the PHPP thermal modelling software and by the Certifier for certification can only be sourced from products that have been specifically tested against the Passivhaus standard. These products are known as Certified Passivhaus Components.
Certified components include windows, doors, rooflights and air handling units. There are also certified wall, roof and floor systems that can be used to construct the fabric of the building.
The benefit of these products and systems is that they are tested and proven to work. The disadvantage is that, as they have been tested, they carry a cost premium.
The ideal certified building would only specify the certified products that are absolutely necessary whilst deferring to generic products with a Passivhaus track record where possible. This is where The Passivhaus Certifier adds value to the process. As they will be interacting with many Passivhaus projects at the same time, Passivhaus Certifiers have a pooled knowledge of non-certified products that work. In our experience, it has been possible to use non-certified windows, doors and rooflights and meet the standard with the guidance of the Certifier; delivering significant cost savings.