Designing an Energy Efficient Home: Can a Passive House Be Beautiful?

The Interest in passive houses (and certified Passivhauses) was already rising before the energy crisis, but now it’s soaring. This approach to design and build creates a home where many elements come together to minimise heat loss, from capturing the sun’s energy to high levels of insulation and a meticulous approach to eliminating draughts.

The result is an airtight envelope where the indoor temperature stays constant, with low energy bills.

To qualify as an official Passivhaus according to the eponymous standard your home must meet several targets, including airtightness and space heating demand. And to gain approval as a certified Passivhaus, those targets are put to the test, post occupancy, by the Passive House Institute.

How Does Energy Efficiency Impact Design?

The more compact a building is – with a low external surface area (where heat can escape) compared to the floor area – the easier it is to be energy efficient. This is known as the ‘form factor’. “It is typical for optimum passive house designs to look to eliminate excessive and complex structures that would increase the overall surface area of the thermal envelope,” says Sam Grew, an architectural technician at Oakwrights, which has designed several certified Passivhauses in oak frame with its own encapsulation system.

This is where passive houses’ reputation for being boring and boxy comes in: in the quest for efficiency, elements that add architectural interest, such as bay windows or complex roof shapes, can end up getting designed out.

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Situated near Bampton in Devon, Sherwood was designed by Gale & Snowden architects; it is dug into a south-facing slope to maximise solar gain and features a striking glazed double-height living space. Super insulated and airtight, its solid internal walls and floor slabs help to reduce temperature fluctuations

However, although Passivhaus standards are strict, they are not so strict that you can’t ‘spend’ some energy on a more complex design and save it elsewhere. “We don’t get hung up on the form factor; it’s important but it’s not the be all and end all. We design something that responds to the site, and the path of the sun,” says Northern Ireland based architect and passive house designer Paul Mcalister.

“You shouldn’t have too many projections, but you can always compensate for that. We worked on a project that was designed to be Passivhaus certified and it did have a lot of projections, so we made the cavities 50mm wider to make it work.” What it does mean, is the more compensating insulation or triple glazing you need to add in, the more costly the build.

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The Barn is a converted agricultural barn and certified Passivhaus in Somerset, designed by Shu Architects. A timber frame structure, insulated with Warmcel, has been placed within the existing barn’s steel frame, with overhangs on the south and west sides to prevent overheating, and triple glazing. Photo: Brett Charles Photography

The Passive House Institute’s Passivhaus Planning Package (PHPP) software allows a house’s designer to measure the essential elements (heat gain and loss, airtightness, etc) according to the design.

“Each site and each client will come with their own requirements and constraints. Perhaps there is an amazing view to the north and you want a huge picture window, for instance. Perhaps the site dictates a less-than-ideal form. The beauty of the Passivhaus Planning Package is that you can try out different scenarios,” says Catriona Kinghorn, an architect and passive house designer at Inverness-based Oberlanders Architects.

If a house is designed with the optimum orientation to harness the sun’s energy, that can also give you some wiggle room to ‘spend’ energy elsewhere. When Catriona designed a Passivhaus, Geanaisean, in her previous role at design-and-build firm Makar, she was working on an advantageous south-facing site.

“We allowed ourselves the inclusion of two rooflights over the central landing, which slightly increased energy loss,” she says. “However, the result is a beautiful light space, perfect for yoga or reading, and daylight is brought down to the lower floor through a slatted timber balustrade – it was worth it.”

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Design and build firm Makar created this 137m2 home in Easter Ross, Scotland, with Passivhaus architect Catriona Kinghorn behind the design. The structure was prefabricated in locally grown timber and the orientation is optimised for passive house design, with a south-facing site, and hill shading to the west, reducing the potential for afternoon overheating. Photo: MAKAR/Catriona Kinghorn

Passive houses are undoubtedly getting more attractive, which Catriona attributes to cumulative experience. “More creative minds are tackling the opportunities and constraints of the standard. Drivers such as energy performance and embodied carbon, while very important, shouldn’t entirely eclipse user experience and aesthetics.”

Beauty has a vital role to play in the sustainability debate: “A building is failing if it doesn’t bring joy to its users. Beauty is not only found in the visual, but in acoustics, comfort, air quality and movement. We should be aiming to create homes that will last 100, even 200 years. If buildings perform as designed, and have a positive effect on their environment, they are more likely to be used in the long term.”

Read More: Embodied Energy: The Key to Low-Carbon New Build Homes?

How to Add Architectural and Design Interest

The spend and save approach to energy and the shape of a building is one way to create an interesting-looking home, but there are more. “Canopies over entrances, alternate offset window-reveal details and clever changes of materials can achieve the visual appeal of a complex shape,” says Sam from Oakwrights.

Sun-shading is essential in most passive houses, ensuring they don’t overheat in summer while optimising solar gain in winter, and many designs make a striking feature of deep eaves or a brise-soleil. External materials have a strong role, whether playing with two or more materials or using something of superior quality, such as stone, to create a polished appearance. Having a talented architect pays dividends: for instance, ordinary timber cladding can turn extraordinary if the design has paid attention to the detail of how and where it meets.

Choosing beautiful, high-quality individual building components can elevate your design, too. Passivhaus-certified products, such as doors and windows, give you peace of mind about their energy-efficiency credentials – as long as they are installed correctly.

Door specialist Urban Front’s e98 passive door, for example, is thicker than its standard door (98mm versus 80mm) with triple rebates for extra weather-sealing – and unlike many certified doors, bespoke options (for the hardwood finish, for example) are available. “The aesthetic is not restricted at all,” says Urban Front’s Elizabeth Assaf.

Planning your energy-efficient home and looking for top-of-the-range products? Browse Build It’s Product Directory of established suppliers

Specifying a Passivhaus Standard Interior

Creating an airtight, insulated thermal envelope has its advantages internally. Consider period properties, where hallways and cellular layouts stop draughts from travelling between rooms, and help keep the heat in: with a passive house, it’s the opposite.

“There’s no problem with big, double-height spaces and having to think about how you keep them warm. There are no draughts, and the whole house is generally the same temperature, so you have that freedom,” says Paul Mcalister. “The only obvious restriction is that you can’t have an open fire.”

One more thing to think about is leaving room for a mechanical ventilation system, an essential element of any house designed on passive principles. “The requirements for an MVHR system mean a designated space is required for its services. Lofts are typically appropriate spaces in which to locate the system, within a ceiling instead of retaining a vaulted roof,” says Sam.

Read More: Designing Out Overheating in Modern Eco Homes

Should You Go For Passivhaus Certification?

There’s no obligation to have your home certified as an ‘official’ Passivhaus – it could simply meet all the standards. In Paul’s opinion, though, certification is a way of stopping the ‘performance gap’ between the projected performance of a home and the actual post-occupancy results: “The moment that you decide not to certify, that’s when corners start getting cut, in my experience,” he says.

For Rhys Denbigh, director of Facit Homes, which makes low-energy prefabricated homes using its own structural timber system, says people want a low-energy home but perhaps don’t want to strive for hard-to-reach targets, especially if it means making sacrifices. “Our projects meet a number of Passivhaus standards: thermal performance with a highly insulated building envelope and triple glazing throughout.”

Our airtightness levels are just outside the certified standard, but it would be possible to reach them,” he says. “However, we prefer to have more flexibility in design, both in terms of the form of the building and the placement and size of windows, so feel that our approach brings the best of both worlds.”

More Inspiration: 10 of the Best UK Passivhaus Certified Homes