CHAPTER THREE
Passivhaus Certification
Certification of buildings, building components, designers and contractors; the process and information required for building certification
Passivhaus Certification is an independent quality-control process designed to ensure that the Passivhaus standard is reliably achieved. A Passivhaus Certificate can apply to entire buildings, building components (including very low thermal bridge components) and building designers and contractors.
Certification of buildings
In order to gain Passivhaus Certification of a complete building, you need to follow a quality-assurance process applied to its design and construction.
Who certifies a Passivhaus?
Certification of buildings can be carried out only by Passivhaus Certifiers accredited by the Passivhaus Institut in Darmstadt, Germany: there are more than 30 of these worldwide. As of summer 2012, there are three Certifiers in the UK: BRE, Cocreate and WARM: Low Energy Building Practice; and one in Ireland: MosArt (see Resources). A Passivhaus project cannot use the same person to act both as Passivhaus Designer/Consultant and Certifier.
Why certify a building?
Passivhaus Certification is all about quality assurance and the avoidance of ‘greenwash’ – the tendency to make unsubstantiated claims about environmental or energy performance. By choosing to get a building certified, those working on a project have access to expertise and advice that will save money and time, particularly if they have little or no previous experience of trying to meet the Passivhaus standard. During the project, many assumptions have to be made, and if any of these are incorrect, for whatever reason, it is easy to go down the wrong design route, especially if this occurs early in the design process. By checking with your Certifier, such assumptions can be checked for validity.
Certification of buildings in the United States
At the time of writing, the only US-based Passivhaus Certifier, the Passive House Institute United States (PHIUS), is not PHI-accredited.1 US projects requiring PHI-accredited Passivhaus Certification now need to go to a certifier outside the United States. However, the PHIUS has formulated its own certification scheme, known as PHIUS+2 – a Passivhaus certification that also includes the US-accredited rating system the Home Energy Rating System (HERS). PHIUS hopes that by linking to the HERS it will increase the recognition of Passivhaus by association, and that someone building to the Passivhaus standard might thereby be eligible for any available US incentives and also be in a better position to qualify under the US Leadership in Energy and Environmental Design (LEED) rating system.
Certification of a building gives all parties peace of mind that it will perform as predicted. This may add some value to the property as Passivhaus Certification becomes more widely recognised as a mark of quality. Certification of a single building in the UK costs from around £2,500, depending on the amount of Certifier input, which is worth clarifying at the outset.
Certification is more important in countries where the standard is not widely understood or recognised. In Austria, where the Passivhaus standard is very common, only one in five Passivhaus buildings now gets certified.
Passivhaus Certificate.
Certification of building components
Typically, the certification of building components3 pertains to mechanical ventilation with heat recovery (MVHR) units, compact units, whole windows, window spacers and window frames. Manufacturers apply to the PHI to get certification. Component certification is priced to encourage manufacturers wanting to sell Passivhaus-certified products. For example, the PHI offers window certification from just over €2,500 (approximately £2,000).
Certified components often cost more than non-certified ones, so a judgement has to be made about the relative benefits and costs of using certified products. This is part of the role of the Passivhaus Designer. There is no requirement to use certified products (except in certain circumstances with the EnerPHit retrofit standard). However, it is worth noting that if a window manufacturer, for example, has taken the trouble to certify some of its products, it is more likely to be able to provide the technical information needed to calculate their energy impact in the PHPP. If selecting a non-certified window, you may be able to obtain an independently verfiable performance specification, but currently it is difficult to obtain this information for many products. Without independently verified figures, it is harder to reach the Passivhaus standard because much more conservative assumptions about the component’s performance have to be entered into the PHPP. It is strongly recommended that you always use a certified model of the MVHR unit or compact unit. The detailed criteria for a Passivhauscertified MVHR are set out in Chapter 7, page 106.
Certified Passivhaus Component logo.
Certification of very low thermal bridge components
At the time of writing, very few products have been certified in this category.4 As we will see in Chapter 8, when building a Passivhaus the aim is to avoid thermal bridges by careful design rather than to use expensive components. Certain types of construction, such as balconies and similar cantilevered designs, make thermal bridge elimination impractical, and in these situations there are certified products that can help. Alternatively, there are other solutions, although they may take the design down a different aesthetic route – for example, balconies can be supported independently of the main structure of the building, as shown in the photograph opposite.
Certification of Designers/Consultants and contractors
There are two ways of becoming a Certified Passivhaus Designer or Consultant. The first involves a short but intensive period of study5 followed by a demanding three-hour written exam. The courses (see Resources) are provided by PHI-accredited Certified European Passive House (CEPH) course providers and the exam is issued and graded by the PHI. The second way involves completing a Passivhaus project that achieves certified status, although this is a more difficult route. Certified Passivhaus Designers are usually architects or others who have specific proven building-focused qualifications, such as civil engineers or building technicians. Certified Passivhaus Consultants come from a wider variety of backgrounds, not necessarily related to construction. In either case, the content of the training and the examination is the same. The PHI’s intention in using the two distinct professional titles is to convey to clients that Passivhaus Designers are able to design a Passivhaus (including doing the PHPP energy modelling – see Chapter 7) and Passivhaus Consultants are able to provide professional support to architects who are not trained in Passivhaus. An architect who is Passivhausqualified may also choose to ‘outsource’ the PHPP calculations to another Passivhaus Designer or Consultant.
Example of structurally independent balconies (building in foreground) and thermally bridged balconies (building in background). Image: WARM: Low Energy Building Practice
Passivhaus Designers and Consultants have to renew their qualification by completing at least one Certified Passivhaus project every five years. They will be competent in using the PHPP, and will also add value to a project by providing consultancy to a design team without Passivhaus experience. Enlisting the help of a Certified Designer or Consultant can reduce the risk of the project failing to achieve the Passivhaus standard, and should save money on the build.
As of 2012, there is now a PHI-accredited Certified Passivhaus Tradesperson qualification (see Resources, PHI). There are a number of providers offering courses leading to the qualification, including a few in the UK and Ireland.
The certification process for Passivhaus buildings
The decision to certify a building can be taken after it is constructed. However, this approach is risky and may deny the project the added value from the input of the Passivhaus Certifier during design and construction.
Ideally, the decision about whether to get the building certified should be taken from day one (see Figure 3.1 on page 45). The pre-planning check shown in Figure 3.1 is usually at extra cost, but may be useful if the project is your first Passivhaus build, as it would provide expert input right at the start.
Rather than reviewing and checking the Passivhaus Designer’s completed PHPP, the Certifier normally produces his or her own separate PHPP calculation using information provided by the Passivhaus Designer, as an independent check. The box below shows the information that the Certifier needs in order to certify that the building meets the Passivhaus space heating requirement (annual specific space heat demand of 15kWh/m².a) in a typical single family house development.
Information required by the Certifier
• Block plan at 1:1250 and/or site plan at 1:200 showing due north and any shading objects.
• 1:100 elevations for each façade.
• 1:50 floor plans showing the internal layout for each floor.
• 1:50 sections showing the airtightness layer and airtightness sequencing.
• Plans showing MVHR ducting (exhaust, intake, extract and supply, including the location of sound attenuators).
• 1:10 and 1:5 plans of all junctions between opaque building elements, and between opaque elements and the doors and windows (head, jamb and sill details).
• Documentary evidence of the types of insulation used, including conductivity value certificates with CE marks (see Chapter 7, page 95) and invoices/ delivery notes. Enough information for the Certifier to enter wall, floor and roof constructions (for the U-values worksheet of the PHPP).
• Photographic evidence of how and where insulation was installed and of how building junctions/thermal bridges were managed.
• Thermal bridge calculations and associated information, where there are junctions that are deemed not to be thermal-bridge-free.
• Information about the windows, including certificates for the key window properties (see Chapter 11) and a window schedule (a list of all windows in the building) showing window designations and dimensions.
• Information about the MVHR system (see Chapter 12), including an invoice/ delivery note and a commissioning certificate.
• Airtightness certificate showing q50 (air permeability – see Chapter 9) for the completed building and a calculation of the internal volume.
• Signed declarations by the Passivhaus Designer / PHPP modeller and building site supervisor.
• If a specific climate dataset has been used for the project, the Certifier will need it, plus evidence of how it was produced (see Chapter 7, page 108).
In order to calculate the total annual primary energy demand, the Certifier also needs:
• Details of: the hot water heating system, properties of the hot water store and any solar thermal facility, and efficiency of the boiler or other heat source.
• Plans or a table showing the lengths of hot water pipes used in the building.
• Information about appliances and lighting.
Figure 3.1 The certification process for a Passivhaus. Note the separate roles of the design & construction team, the Passivhaus Designer and the Passivhaus Certifier. Source: WARM: Low Energy Building Practice6
RECAP
In a country such as the UK, where Passivhaus is relatively new, certification is particularly beneficial. It provides a quality-control system as well as a framework for spreading low-energy-design skills. There are many claims made about buildings and their eco-credentials, and certification helps to protect against ‘greenwash’, which unfortunately is still common in a culture where we are not yet well informed about low-energy design. Certification may become advantageous when selling on a Passivhaus, as awareness of the concept spreads.
Certification in the UK can apply to whole buildings, building components and people. Designer or Consultant qualifications can be gained either through study or through completion of a Certified Passivhaus project. A building can be certified after completion, but there are considerable advantages to involving the Passivhaus Certifier from the beginning of the project.