What is Passive House design, and what does it mean for sustainability?
While it may sound like the latest dance-music craze, Passive House is actually an ambitious building design standard that is changing the way we think about sustainable homes. We speak to a couple of Passive House professionals to better understand this game-changing approach to building houses.
What is Passive House (or Passivhaus)?
Passive House, known originally as Passivhaus, is a German design standard pioneered in the 1990s, which – put simply – aims to deliver a comfy, healthy and energy-efficient building. Since its inception over three decades ago, the Passive House approach has been embraced around the world – including right here in Australia, where it is helping to transform our approach to sustainable housing.
According to the Australian Passive House Association, buildings produce just under half of Australia’s greenhouse gas emissions – 23% of which are predominantly from heating and cooling. As Australian temperatures increase and the climate crisis unfolds, Passive House has the capacity to help tackle this issue head o
“It's definitely the highest level of construction and execution there is for sustainability,” says Michael Nowlan – head of design at The Sociable Weaver, a Passive House-accredited design and build firm. “In Europe, it's widespread – that’s how they build. And it’s the level housing needs to get to here [in Australia] to not impact global warming or have increasingly massive energy bills.
A step up from the increasingly popular Passive solar heating approach, a Passive House build controls the temperature of the house, meaning that heating and cooling is not required. “A Passive House building remains between approximately 22-25 degrees, reducing the energy use for heating and cooling by around 80-90%,”” says Alexia Lidas of the Australian Passivhaus Association. Not only is this good for the environment, it ensures a safer, more comfortable living or working space as we experience increasingly volatile weather conditions in Australia.
All of this is achieved not through specific technologies or materials, but by applying design principles that are rigorously performance tested and hyper-specific modeling, which takes into account the individual site location and occupancy numbers of a building. And the principles can be applied to new build or retrofit.
Passive House design principles
The concept of Passive House is based around five key design principles:
- Thermal insulation
- Mechanical ventilation heat recovery
- High performance windows, and
- Thermal bridge-free construction.
All of which sound very technical because, well, they are.
What these design principles essentially set out to achieve is that your house is warm in winter, cool in summer, full of fresh air and natural light.
“We buy cars that have quality assurance, but we don't apply the same to our buildings. When you think about your house,” says Alexia, “you've got your whole family sleeping in a house overnight, but you don't know what's coming in through your ventilation. There are all of these health risks and benefits that buildings can bring to you, and you are provided with assurance of these with the science and validation of Passive House.”
Let’s break them all down.
Relax, this doesn’t mean living in a sealed-off box (which would be extremely impractical in the Australian climate). What Passive House design involves is sealing the “envelope” (the bit between the inside and outside) of the house so no hot or cold air leaks in or out – meaning, that when doors and windows are shut, you can control the temperature without the intrusion of the outside elements.
With a Passive House approach, your home becomes a kind of bubble that you can open and close – which means controlling the air we breathe. “If there was a bushfire like we’ve seen in recent years,” explains Michael, “it helps to control that bad air quality.”
Aka: really good insulation! Thermal insulation for Passive House design certification needs to be continuous and, in some cases, could be higher than the National Construction Code advises, depending on where you live. This drastically reduces things like condensation, mold and cold surfaces in winter.
Mechanical ventilation heat recovery
While this sounds like a gadget the Ghostbusters might use to vaporise ghouls, it’s actually a method of reducing the need to open your windows, thereby improving indoor air quality. How does it work? A MVGR unit recovers unused cold and warm air that would have otherwise gone to waste and also filters air that does come into the house. This means less pollutants and less condensation.
Windows play a big role in Passive House design. This means having the right sized windows placed strategically to capture the right amount of sunlight, and ensuring those windows are well sealed with double or triple glazing.
Thermal bridge free
According to Sustainable Homes Australia, a thermal bridge is a space where heat and cold can escape from inside to out, or vice versa. This can happen through the floors, walls or roof components of any house – a big issue for controlling a building’s climate. Passive House design aims to stop this conduction of heat/cold by using continuous insulation (with minimum penetrations), and where this isn’t possible, by using materials that are less likely to conduct heat. Ultimately, this helps decrease condensation and mould while controlling temperature.
Passive House design in Australia
Australia has some extraordinary examples of Passive House design – both big and small.
“The largest number of Passive House buildings in Australia is actually in a residential space,” says Alexia. “However, we're starting to see some outstanding buildings come to life in the commercial space.” If you are interested in seeing the breadth of building happening here, The Passivhaus Association's Building Register is a great place to start. But there are also some really innovative public and commercial buildings that are worth a visit to marvel at how this approach can be modeled on a large scale.
Gilles Hall – Mornington Peninsula, Victoria
Monash University’s student accommodation Gilles Hall is the first large-scale building to achieve Passive House certification in Australia, and the largest example of the design approach in the Southern Hemisphere. Located on Victoria’s Mornington Peninsula, it contains 150 studio apartments across six levels, plus shared areas designed to instill a sense of community.
Cornerblock – Gold Coast, Queensland
Cornerblock is a new commercial office space located on the Gold Coast, which was designed with the express purpose to create a workspace that prioritises energy-efficiency, sustainability and human well-being.
German International School – Sydney, New South Wales
It makes sense that a German school would be one of the first education institutions to embrace Passive House. Their innovative cross-laminated classrooms recently won the prestigious Sustainability Design Award.
ANFM House – North Melbourne, Victoria
This luxury award-winning boutique hotel, run by the Nurses Union, is located opposite the famed Vic Markets and is a stylish example of just how impressive Passive House can look and feel.
What’s involved with Passive House certification?
There are three levels of Passive House Certification – Classic, Plus and Premium – each with different requirements for heating, cooling and energy demand levels. The certification process starts from the design and runs right through to a testing stage at the end of the build to ensure performance. The most efficient way to approach a Passive House build, suggests Michael, is to engage a Passive House certified designer, builder and an independent Passive House Certifier. That way you have a team to guide you through it from start to finish.
“There's a lot that goes into it, a lot of numbers need to be looked at,” says Michael. “But the client doesn’t need to know how all this works or be experts. That’s why we as professionals have done the Certification course. [As a designer and builder], we run that process from start to finish, and then get the outcome you want to achieve. We hold the client’s hand through the process.”
If you want to build a Passive House, you can engage any certified Passive House architect, or Passive House builder to start the process. And there are even excellent prefabrication options, “In fact, prefab and Passive House go hand in hand,” says Alexia.
The cost of a Passive House in Australia
Money is always front of mind when people are approaching a new build, renovation or extension and there are additional costs involved when undertaking a Passive House build. However, future savings on power bills are likely to quickly offset this initial investment. And once completed, it could cost as little as $100 a year to maintain.
“I would say people spend roughly $100,000 extra on a complete design and build for Passive House,” says Michael. “But that is then paying itself off within 5 to 10 years.”
It’s difficult to put a specific number on it as the builds differ so significantly from site to site. “It's important to consider that a Passive House is built to perform according to the local climate, which can also impact the cost, so percentages are not easy to provide. We see price differences anywhere between 10-20% extra, sometimes 30%,” says Alexia. “But in addition to savings on bills, we also know there is a potential for higher rental yield and purchase price for sustainable houses.”
The way of the future
Quite simply, Passive House design is the most sustainable and healthy form of housing available that takes pressure off the grid and drastically reduces energy bills. “They are clean, healthy, quiet buildings that are much better for humans and create happier places to occupy,” says Alexia. “This is really low hanging fruit and a pathway to net zero. Who wouldn’t want that?”
Want to learn more about Passive House?
Check out the following resources:
Australian Government’s Passive House: Your Home website.
Learn about Bank Australia’s Clean Energy Home Loan, which offers reduced interest rate for people looking to buy, build or renovate to achieve a planet-friendly, energy efficient home.