Passivhaus homes deliver steadier loads that support grid stability. But whole-house integration at scale requires coordinated design, manufacturing and building disciplines.
By embracing the Passivhaus standard, Australia could have a powerful tool to fast-track our journey to net-zero emissions.
Combining super-insulation, airtight construction, high-performance glazing and balanced mechanical ventilation, Passivhaus projects drive down heating and cooling energy use by up to 90 per cent compared to conventional buildings. Though still a niche – with just 70 certified projects to date – Australia now has more than 200 Passivhaus schemes in development.
To understand how the rigorous fabric of the standard can be leveraged to meet net-zero goals, create delves into ultra-tight envelopes, advanced modelling, prefabrication strategies and building Passivhaus residences at scale.
Getting the envelope right first
Passivhaus is much like an aircraft, said Scott Stewart, who was in the Air Force for 20 years before becoming a Certified Passivhaus Designer, at the recent Sydney Build Expo.
“It’s an integrated whole, a system of systems.”
By locking in the thermal envelope first to prevent draft and heat transfer, everything else falls into place.
“The software doesn’t touch any of the toys – hot water systems or solar panels – until we solve the envelope problem,” he said.
This allows the house to maintain at least 20°C in winter – not just during the day, but overnight as well.
“That means no more cold drafts under the windows, no beanies at bedtime and no morning shivers when you get up to use the loo.”
In summer, the goal is to keep the house below 25°C, maintaining roughly 60 per cent relative humidity.
“Imagine stepping inside from 28°C with 80 per cent humidity into a house at 25°C and 60 per cent humidity – that’s instant relief,” he added.
There are small temperature excursions, with one room perhaps reaching 26°C while another drops to 24°C. But overall, by keeping the whole house within that narrow band, the big heating and cooling peaks are avoided.
“Across NSW – and Australia more broadly – the grid sees huge spikes between 7-9am and again from about 5-9pm – when everyone comes home and fires up their 30-50 kW air-conditioning systems,” Stewart said. “By designing homes that stay naturally within 20-25°C, we flatten those peaks and drastically reduce reliance on the grid at its most stressed times.”
Read more: This low-energy housing solution could revolutionise building standards
Modelling to strike a balance between comfort and carbon
Even in net-zero designs, comfort shouldn’t be considered a luxury – it’s a non-negotiable, said Elise Wang, pH101 National Coordinator, Australian Passivhaus Association.
“There’s no sensible approach to net-zero operational carbon that forces people to wear jackets indoors in winter,” she said. “If we think of net zero as operational energy equating with renewable supply, we can’t just build inefficiently and add more solar. That overloads the grid.”
To tackle this problem in practice, the Passive House Planning Package (PHPP) provides an interface where every junction – from window sills to roof-wall connections – is modelled, Wang said.
“PHPP is an Excel-based energy-accounting tool that lets us quantify every heat loss and gain in a building.”
By leveraging Excel’s What-If Analysis, her team can instantly toggle insulation resistance values from R-4 to R-5 or R-6 – observing the impact on annual heating demand in real time.
“This immediate feedback allows us to iterate design choices collaboratively during meetings, ensuring that each decision brings us closer to an optimally efficient thermal envelope,” she said.
Simon Anderson of Anderson Architecture described how his practice has pushed this balance to the limit with an award-winning home that PHPP predicted would produce four times its energy use – only to export 1.5 times its demand once pool pumps and EV charging were included.
“The lesson? A tight envelope changes everything … ensuring we don’t just dump more solar on a leaky house.”
Modular manufacturing for precision production
Offsite manufacturing is gaining traction as a way to marry precision with Passivhaus performance, particularly through structural insulated panels (SIPs), said Elena Cazacu, registered architect, certified Passivhaus designer and founder of Evissa.
“Our SIPs embed continuous insulation with inherent airtightness, ideal for Passivhaus,” she said. “By applying Design for Manufacturing and Assembly, 80 per cent of our effort goes into millimetre-perfect detailing so panels arrive on site ready to slot together.”
However, when materials are prefabricated for a single project, an entire manufacturing process is set up just for that job – quickly becoming expensive and onerous, Cazacu said.
“Economies of scale obviously come from repetition. And by repetition, I don’t mean building the same structure over and over – instead, we look for opportunities to automate processes and swap components without having to replicate the exact same design each time.”
Upgrading existing homes
Can you build a Passivhaus extension on a traditional structure? Yes, but it’s complicated.
Retrofitting a Passivhaus demands a series of nuanced decisions that balance sustainability, practicality and the lived experience of occupants – particularly when working within the envelope of an existing building, said Linden Thorley, Principal Architect, Linden Thorley Architects and Retrofit Taskforce Co-Chair, Australian Passivhaus Association.
“If you were to build a new Passivhaus at the back of existing buildings, you’ve done a great job of minimising what you had to build and what you’ve got,” he said. “But the practicality of living in that house is where it really becomes difficult, because once you’re in the nice comfortable part out the back, you’re unlikely to want to go into the front.”
However, preserving foundations, walls, and rooflines wherever feasible can drastically reduce embodied carbon and cost. And because the construction industry contributes roughly 60 per cent of landfill waste, material reuse becomes an ethical imperative, Cazacu said.
“It’s important to think about what’s worth keeping. Is it already affected by mould, rot or moisture? Has it degraded beyond repair? Or might it still be viable to retrofit? That’s a conversation we need to have at this stage.”
Driving growth at scale
Using a lean methodology can support engineering for scalability, advised Ibrahim Amin, co-founder of Marvel Homes, who has built five certified Passivhaus residences.
“We reviewed the different materials we work with and realised that our true bottleneck was our contractor and trade base – their training and skill levels simply didn’t allow us to scale,” he said. “So we stepped back and re-examined our core principle: what is actually possible? That led us to the concept of the ‘lean’ Passivhaus.”
A lean Passivhaus combines the rigorous energy efficiency and comfort standards of the standard with the principles of lean design and construction. This approach seeks to deliver high-performance, healthy and comfortable homes while minimising waste, cost and carbon footprint.
“We analysed the contractors, [tradespeople] and their skillsets to decide which fields and construction details to adopt – ensuring everything complements both their existing strengths and the Passivhaus standard,” Amin said.
In collaboration with Stewart, Amin developed a system covering every phase from material selection and design, through to implementation and construction details.
“This guarantees we’ll hit our performance targets, meet every installation requirement and ultimately deliver a healthy, energy-efficient and certified Passivhaus.
“We can already see how it can expand further and ultimately serve as a catalyst to accelerate the broader development of certified Passivhaus projects.”
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Conditioning technologies are critical in these as well as other normal leaky houses. It is – I think -disappointing to see for example a split system used for air-conditioning in several of these Passive House designs. As innovators of radiant hydronic systems, we have studied and investigated principles and methods of conditioning spaces according to comfort – not temperature. This language and understanding is however missing from Passive House articles. Air movement, ventilation, radiant exchange and surface temperatures as well as solar exposure and solar shading technologies…are not shared or explained to the reader….which are actually the attributes that should make a Passive House different from the norm.
We continue to talk ‘Air Temperature’…. when it is actually ‘Operative Temperature’ which gives us Comfort. Spaces that offer radiant, air movement, ventilation (fresh) air, humidity control and yes o.k. dry-bulb air temperature (note intent of stating this LAST), can provide us with far better comfort that just blowing air through a space! (Aaaargh… Split Systems!) If Passive House is going to be something different, for me, it would be this, the conditioning of a space. In fact, our company tests and researches VERY leaky rooms with LARGE (75% window to wall) glass areas, and gets excellent comfort conditioning results for a space….because we combine radiant with, air movement, convection and ventilation systems. What is missing from most if not ALL of the Passive House articles is a detailed explanation that provides a ‘feel’ of why the house is different. We recently had a few visitors step into our hydronic radiant / ventilated conditioned TESTCELL and it was within a minute that people remarked how it was special, different, comfortable, to no other comparison. For us this is what spaces should provide! I would almost go as far to say, who cares if they are insulated to the hilt and airtight as….fine and o.k. for some…but this construction can also lead to indoor problems if not dealt with properly. So, stating that a building or space is ‘air-tight’ doesn’t resonate always with comfort. Sure, we don’t want a sieve and draughty building…but we don’t exactly need one completely air-tight either!
I guess what we are trying to say is that technology exists to serve architecture. So attemping to get a better understanding of how it can or does is important. Passive Houses are different…or should be different. Why? How?