What is a Passivhaus Designer?

As a Certified Passivhaus Designer, I am often asked what exactly they do, what can they bring to your Project? 

The international Passivhaus Standard is a clearly defined and rigorous standard for energy efficiency, comfort and quality assurance of buildings.  Designing a building to achieve the standard requires detailed knowledge and a rigorous methodical approach to design and documentation.  Employing a Certified Passivhaus Designer ensures that your Building stands the best chance of performing to this rigorous standard.

A Certified Passivhaus Designer, regardless of their prior qualification, works across disciplines on a Passivhaus project. Their role integrates architecture, structure, building services, building science, energy modelling and construction detailing. They will at times both support and challenge the other designers on a Passivhaus Project.

The individual also does not need to be completely independent. They can also be the architect, structural engineer, building services engineer, or another consultant on the team; fulfilling two roles has many advantages, bringing consistent detailed knowledge and a rigorous methodical approach to the design of your home to meet the international Passive House Standard.  At Novo, we regularly work with other design teams in an advisory capacity.

A Passivhaus Designer is trained in the fundamentals of Passivhaus design. This includes the ‘hard requirements’ – 10W/m2, 15kWh/m2.a heating/cooling demand, 120kWh/m2.a Primary Energy, 0.6ach, etc, as well as the ‘soft requirements’ (comfort and hygiene criteria) and the functional definition of a Passivhaus building. Check out our Blog Post What is Passivhaus? for more information.

With a good knowledge of the fundamentals, a Passivhaus Designer is able to communicate the benefits of Passivhaus to a client, as well as the advantages and features. They are also able to communicate the impact on the design process and design outcomes to other designers on your Project team.

A key to Passivhaus design is identifying the aspects of heat energy balance that the building design can influence; where heat is gained and lost due to the design of a building.  Key strategic design strategies include building shape / mass, glazing, shading, insulation / thermal bridging, airtightness and ventilation. These are important for both energy efficiency and comfort.

Quality control is also key to Passivhaus design. The design of the thermal envelope needs to be rigorous to ensure that insulation and the airtight barrier is continuous and effective when built. U-values need to be robust and reliable. Thermal bridges need to be eliminated by design or thermally modelled.  Detail design is key at this stage as well as monitoring execution of these details on site.  All areas where the Passivhaus Designer can assist your team.

A Passivhaus Designer is also trained in space planning for Passivhaus. How internal rooms and spaces relate to solar heat gains, internal heat gains, ventilation and building services all need consideration as early as possible. Space planning can have a considerable impact on the ease and cost effectiveness of achieving the Passivhaus Standard.

The final aspect of Passivhaus design is the building certification process. A Passivhaus Designer can guide a client and team through the process, but cannot certify a Passivhaus building. Only an independent Passivhaus Building Certifier can certify that a building meets the international Passivhaus Standard requirements.  Of course, you do not have to have your building Certified, simply following the principles of Passivhaus will ensure that your home performs well above that of 'standard' homes.

Can it be Built and will it be Airtight?

Most buildings suffer from a performance gap between the design predictions and the actual building performance. Passivhaus effectively eliminates the performance gap. Part of this success is due to the care and attention to construction detailing. This ensures that what is designed can and will be built as intended and that it meets the requirements of the Passivhaus Standard.

Many aspects of a design are fixed during the design stage and ideally never get changed during construction. Regardless of design, several critical aspects are still dependent on good construction quality, though. These include;

• Glazing – weatherproof and airtight installation without thermal bridging is needed.

• Airtightness – a continuous, unbroken, air barrier is needed.

• Insulation – continuous installation without thermal bridging or gaps is needed.

• Ventilation – correct, high-quality installation and commissioning is needed.

Too often architects and designers draw details that aren’t easy to build. This can result in compromised quality and performance when constructed (as well as headaches for the builder), or on site changes being necessary. Neither of these outcomes is ideal for any project and part of a Passivhaus Designer’s role is to help avoid them. A Passivhaus Designer will review all construction details with an eye for how the continuity and integrity of the building envelope will be delivered.  They will be looking at the weather proofing, the insulation, the air barrier and the buildability of the detail.

Airtightness often needs additional care and attention as the Passivhaus requirement of 0.6ach is still perceived as a challenge by many in the industry.  It is, therefore, critical, that the design, detailing, and documentation makes it as simple, straightforward and clear as possible to understand the airtightness strategy and to achieve it on site.

A Passivhaus Designer’s role with regards to airtightness may extend to providing toolbox talks and installer briefings on site. Explaining the purpose and methodology to achieve an airtight building envelope often helps to raise aspirations on site. It also reinforces the important contribution each trade can make to the quality and performance of a building.

Site support is also very important, visiting the site and observing construction progress is a critical role of the Passivhaus Designer.  With their specialist training and understanding of what details matter for Passivhaus, a Passivhaus Designer may spot something critical that an architect or clerk of works doesn’t. They should also be able to assist in resolving any issues that arise to ensure your building has the best chance of performing to the standard.

Building Services, even for Architects

Integrated design is vital for successful Passivhaus design. And building services are an important part of any building design. A Passivhaus Designer, even if they are an architect, is trained in the design of building services for Passivhaus.  Building services include ventilation, heating, hot water, lighting, and appliances.

Ventilation is the most important of these and given the most detailed consideration.  For ventilation and heating, the starting point is the comfort (and hygiene) requirements of the international Passivhaus Standard.  Ventilation is needed to provide fresh air and to remove odours, pollutants (CO2, VOCs), water vapour (humidity control for comfort and to avoid mould etc) and excess heat (summer cooling).  Additionally in Passivhaus buildings, the ventilation system preheats incoming fresh air (via the heat exchanger) to avoid cold draughts and filters out dust and pollen.  In some but not all Passivhaus designs, the ventilation also delivers the heating.

A Passivhaus Designer is trained in designing the ventilation system and the related duct sizing and layout.  This is an important part of an integrated design and a very useful skill for an architect to have if they are also a Passivhaus Designer.  The ventilation system design is ideally developed at the same time as the architectural design.  This way spaces for the equipment and ducting can be intentionally allowed for rather than shoehorned in later.  It also means both energy and cost effective locations for equipment can form part of the design.

Early design decisions relating to the building services can have a big impact on the cost-effectiveness of a Passivhaus design.  A Passivhaus Designer can help ensure intelligent design decisions are made to keep costs in check. 

Hot water makes up a noticeable part of energy consumption in a Passivhaus building.  User choice and patterns of use can have a huge impact on this and are out of a designer’s control.  Heat loss from the distribution of hot water is less dependent on actual use patterns and can, therefore, be minimised through Passivhaus design.  This is important to reduce energy consumption.

Artificial lighting also makes up a noticeable part of energy consumption in a Passivhaus building.  The first approach a Passivhaus Designer will take is to minimise the need for artificial lighting by good daylight design.  After that, it comes down to efficient layouts, sensible light levels and selection of energy efficient fittings.

A Passivhaus Designer brings an integrated cross-discipline design approach.

• Passivhaus design is optimised integrated design.

• A Passivhaus Designer is trained and knowledgeable in the fundamentals of the international Passivhaus Standard, the building science of Passivhaus, the construction of Passivhaus, and building services for Passivhaus.  They bring all these aspects of the design together across multiple disciplines to ensure the success of your project.

• A Passivhaus Designer can also be the architect or engineer on a project, or they can be independent.  In either case, it is best that they are an integral part of the design team and process.

• It can be beneficial to a project if the architect and engineers are trained as Passivhaus Designers, even if they don’t carry out the role of the Passivhaus Designer on the project.  The knowledge and the mindset of a Passivhaus Designer brings considerable benefit to their way of designing within their own discipline.

As Certified Passivhaus Designers, Novo Design Studios is well placed to advise you on any questions that you may have.  We not only love incorporating Passivhaus principles into our own work, but love helping other design teams reach improved energy efficiency standards in their Projects.  If you think we could work together on your next project, then please contact us and we will be in touch to discuss how we might work together.