Beyond the Product: What does Passivhaus mean for Facade Design?

Low-energy buildings are putting greater focus on what the building envelope needs to deliver. For facades, that means looking beyond a single U-value and considering how the glazing, aluminium system, interfaces, ventilation and installation work together. Passivhaus, also known as Passive House, brings those elements together within a demanding approach to building performance.

There is an important distinction though, between Passivhaus certification and Passivhaus performance, and that applies to products as well as buildings. Individual facade products can be independently certified as Passive House components. Other products may not carry that certification but can still provide thermal, airtightness or other performance characteristics relevant to Passivhaus or high-performing building.

Both are relevant to high-performance facade design. The important thing to understand is what the project requires: a certified component, particular Passivhaus performance levelts, or a wider combination of thermal, acoustic, weather and security requirements.

We spoke with Rebecca Thompson, Technical Advisor and Passivhaus expert from our technical team about what that means in practice, where facade performance can be won or lost, and why the conversation needs to go further than just choosing a product. Rebecca supports fabricators and consultants with technical queries and early-stage facade design.

What does your role involve when you're supporting high-performance facade projects?

It's quite varied, which is one of the things I enjoy about it. I deal with day-to-day queries, so that could be anything from helping somebody find the right information in a system manual to talking through how something works in practice.

I also work with project teams much earlier in the design process. We can carry out technical pre-studies before estimation, provide preliminary structural calculations, supply guidance around wind loads, and look at typical spans and inertia requirements. It's really about helping people understand what's achievable before they've gone too far down a particular route.

We can also advise on U-values, acoustic performance using TechAcoustic, hardware choices, weather performance and security requirements. Every project asks something slightly different of the facade, so the first job is understanding what that particular building needs.

What does a high-performance facade actually mean?

It depends on the project. "High-performance" is one of those phrases that gets used a lot, but unless you define what you're trying to achieve, it doesn't tell you much. For one building, thermal performance and airtightness might be the priority. On another, acoustics might be particularly important because of the location. Somewhere else, there may be demanding security or weather-performance requirements. That's why I always start by asking: What does high-performance mean for this building?

Once you know that, you can make sensible decisions about the facade system, configuration, glazing and other details. It's quite easy to focus on getting the lowest possible U-value, because that's a number you can compare, but that doesn't necessarily tell you whether you've got the right facade for the building.

What's the difference between Passivhaus certification and Passivhaus performance?

It's worth being clear about this because we can talk about both the building and the products that go into it. A building pursuing Passivhaus certification needs to meet the requirements of the standard as a complete building. It's not a case of getting one particularly good U-value or airtightness result for one component and then calling the building Passive House.

Products have a similar distinction. There are facade products on the market that have been independently certified as Passive House components. There are also high-performing products that don't carry that certification but can still deliver individual performance levels that are relevant and applicable to a Passivhaus or other high-performance building certification. Both can therefore be relevant, but they're not the same thing.

For us, the important part is understanding what the specification is asking for. Does the project require a certified product? Is it targeting a particular thermal or airtightness performance? Or does it have a combination of thermal, acoustic, weather and security requirements? Once that's clear, we can look at the system and other applicable components and work through what's appropriate. What we avoid is over-specifying or assume that meeting one or two individual performance targets make the product or building Passivhaus certified.

What changes in the facade when you're working towards Passivhaus requirements?

Airtightness becomes a major consideration, but it can't be looked into on its own. You can't choose a high-performance window or curtain wall solution and assume that's the performance sorted.

The glazing specification and configuration matters. And the interface between the facade and the rest of the building matter even more. That's where the detailing comes in.

You can start with a very high-performing system, but the completed facade still depends on what happens when it meets the surrounding construction. It's why we try to have these conversations sooner rather than later. You're not looking at products in isolation, you're looking at how all the different parts are going to come together on the actual building.

What should fabricators know before taking on a Passivhaus certified or performing facade project?

There can be practical differences in the workshop, and they need to be allowed for. Depending on the performance requirements and system being used, you could be dealing with larger profiles, foam inserts or additional assembly stages. That can affect the fabrication process and the amount of labour involved. You'd rather understand that before you've priced and programmed the work than discover it when fabrication starts.

Fabricators don't need to turn themselves into Passivhaus specialists overnight. What they do need is a clear understanding of the system they're making, what performance the project requires and where particular details need more attention.

And if you're unsure about something, ask. There isn't much point in making an assumption in the workshop and finding out later that the detail needs to be done differently to achieve the performance you need.

Why are facade interfaces so important for airtightness and thermal performance?

Becuase that's where different parts of the building meet. Achieving a low U-value isn't only about choosing the right frame and glass. You also need to think about how the system connects to the building and how the intended thermal and airtight layers continue through those junctions.

You could have a very good facade package, but if the surrounding interface isn't properly considered, the completed installation may not deliver what was intended. That's why those details shouldn't be left until the project has started on site.

The design team, facade contractor and installer all need to understand how those junctions are supposed to work and who is responsible for delivering them. It's much easier to sort that out while you're looking at the detail on a drawing than when installation is already underway.

How do you balance Passivhaus airtightness with ventilation and everything else the building needs to do?

You have to come back to what the building needs. An airtight building still needs ventilation, the two performances aren't opposites. The point is to control unwanted air leakage while providing ventilation in the way the building has been designed to use it.

From a facade perspective, that might involve automated ventilation, BMS-controlled openings, tilt-before-turn openings or trickle vents, depending on the project. Those decisions need to sit alongside the airtightness strategy rather than being added afterwards.

It's another reason why I would not advise to the look at the product with the lowest U-value and automatically assume you've found the best solution. People still have to use the building. You should think about ventilation, acoustics, operation, security and weather performance alongside the thermal requirements.

How much difference does installation make to Passivhaus facade performance?

A lot. You can specify a good system and work everything in the modelling, but someone still has to build it. Sealing. fixing points and the interfaces all need to follow the design intent. If those details aren't installed correctly, you can undermine airtightness, thermal continuity and weather performance. That's why I would advise not to treat installation as a separate conversation that happens at the end.

The people delivering the facade package need to understand what has been designed and why particular details matter. You can do plenty of calculations before, but the completed building is what counts. Installation is where the design on screen becomes the facade on the building.

What's your advice to someone starting a Passivhaus or high-performing facade project?

Start by being clear about what you're trying to achieve. If the project is working towards Passivhaus certification, establish that. If it requires Passive House certified products, identify that too. If it's targeting particular thermal, airtightness, acoustic or weather performance levels instead, make those requirements clear. That distinction makes the conversation much clearer from the start.

Then look at the facade as a complete package. The system, glazing, interfaces, ventilation and installation all affect the result.

Finally, use the expertise available to you. The TECHNAL team work with key stakeholders to understand the brief, define the performance requirements and look at which solutions are appropriate. You don't need every answer before you speak to use. Usually working through the questions is where you start.

Final Thoughts

Passivhaus places demanding requirements on building performance, but the façade isn't defined by one figure or one product. Certification and performance need to be understood separately, both at product and building level. A Passive House certified component provides independently assessed performance, while other high-performing façade products may also be relevant where the project is targeting specific performance requirements.

For Rebecca, the practical point is simpler: establish what the building needs first, then consider the system, glazing, interfaces, ventilation and installation together.

Working on a Passivhaus or high-performance facade project?

Talk to the TECHNAL team about façade system selection, thermal and acoustic performance, technical pre-studies and project-specific detailing.

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