Built Intelligence

What are Passivhaus Buildings - Darren Evans

What are Passivhaus Buildings - Darren Evans

Buildings designed, constructed, and certified to the Passivhaus standard are highly energy efficient, and at the same time provide high levels of comfort for occupants. The Passivhaus standard can be applied to any and all building types, not just domestic and residential construction.

The rigorous scientific principles that underpin the Passivhaus concept can make the standard seem like a performance standard only, but it is, first and foremost, a comfort standard. It’s not uncommon for people to say that a building follows the principles of the standard, and in this post, we’ll explore what they might mean by that and why it might not deliver the desired result.

What makes a Passivhaus building ‘passive’?

The Passivhaus standard (also written as ‘Passive House’) utilises the principles of passive building design to deliver its performance and comfort goals. It focuses heavily on the planning and layout of buildings to achieve an efficient form factor (the ratio of a building’s external surface area and volume), control solar gains throughout the year, and maximise daylight, to reduce reliance on mechanical (‘active’) systems.

Inevitably, active systems are still required to some extent. Limited space heating is required, together with a means to heat water. And the standard favours mechanical ventilation, almost exclusively with heat recovery (MVHR), to provide the desired indoor air quality levels.

The principles of passive construction were not new when the Passivhaus standard was established. History shows us many examples of buildings designed to respond to the prevailing climate and keep people comfortable, whether in hot or cold places. Over time, various experimental projects played with those principles, and sometimes added different technology, to create various one-off solutions.

What the Passivhaus standard did was to create a measurable approach that could be applied to building designs of any type, regardless of construction method, location, or end use. It made it possible to know that the finished building would deliver the intended result.

The result is a building with extremely low energy consumption, whatever the climate. The standard is not prescriptive in how to achieve that result, only what end result to achieve. It does not necessarily mean compromising on aesthetics or design, though broad design themes do tend to arise.

How is a Passivhaus building created?

Whether you are a client, architect, housebuilder/developer, contractor, or M&E consultant, if you are part of a Passivhaus project in any way then it will likely require you to go about your role in a different way than “normal”.

This can be one of the downsides of pursuing Passivhaus certification. If the people involved on a project don’t have experience of working to the standard, then they effectively have to gain that experience on the project in question. For the inexperienced, the extra time and cost compared to ‘business as usual’ is often what leads to the perception that Passivhaus is more expensive over a more ‘typical’ approach to construction.

To assist with this different approach, designers, consultants, and tradespeople can undergo training and examinations to become ‘Passivhaus certified’ professionals. While it is not an obligation to use people with such certification, their training means they have the knowledge and ability to apply the standard’s principles of quality assurance to their work.

For example, engaging a certified Passivhaus Designer on a project in its early stages can help to ensure that the right decisions are taken from the outset, thereby avoiding costly and time-consuming changes at a later stage. They can use the Passivhaus Planning Package (PHPP) software – another unique feature of the Passivhaus standard – to analyse options and carry out initial checks that all the standard’s fundamental criteria can be met.

Further into the project, they can then run a more detailed PHPP analysis to fine tune the design and establish key details and performance specifications. A contractor – whether Passivhaus-certified or not – can then go into the project fully aware of what is expected of them.

How is a Passivhaus building quality assured?

Multiple quality assurance requirements must be met for a building to be Passivhaus-certified. They include the following.

  • PHPP must be used.
  • The internal surface temperature of the windows must not drop below 17 degrees C on the coldest day of the year.
  • Photographic records must be kept.
  • The contractor must write a declaration that the building is constructed in accordance with the contract.
  • The energy performance requirements for the local climate have been met (these include targets for heating demand, primary energy demand, and airtightness).
  • Professional commissioning of services specifically of the installed ventilation system

On some projects, people might choose to adopt some or all these requirements with the intention of getting a building that performs like one certified to the standard, but without going through the full certification process.

Achieving all of the standard’s quality assurance requirements but not obtaining certification is seen as satisfying ‘Passivhaus principles’. Only meeting some of the standard’s performance elements, or simply adopting general passive design techniques, should not be confused with meeting the Passivhaus principles or achieving Passivhaus certification.

Only by meeting the requirements of the Passivhaus standard and measuring it through a PHPP assessment can you be sure to achieve the quality of a Passivhaus. Monitoring of certified Passivhaus buildings routinely shows them to meet the expected performance levels in service. In other words, there is little or no performance gap – and that is, ultimately, what differentiates a Passivhaus building from the rest.

About the author 

Darren Evans - Business leader connecting with people to treat people and planet as the precious resources they are so that we can build a better future together  https://darren-evans.co.uk/ 

As part of our low energy design and sustainability consultancy, Darren Evans can provide certified Passivhaus Designer services for your project. To find out more about how we can support your next project and help you to achieve a Passivhaus building, contact the team at Darren Evans.

Sign up to the latest free webinars on NEC3, NEC4, CDM, JCT and more.