passive house design

Last week’s Spinifex calling for Passive House to become a new standard for the National Construction Code certainly struck a nerve. Here are three views: from Smart Plus Homes’ Passive House design trainer Daniel Kress who says it’s a step, not the whole staircase; ComfortID’s Erwin Boermans who wants to see mechanical heating and cooling systems replaced with water-based systems; and Troppo director Phil Harris  who says we need to stay in touch with the weather and that “there is nothing worse than concrete in the tropics.”

More than a dozen comments on our website raised some crucial questions around the Passive House standard. There were concerns about its suitability for the Australian climate, cost implications, issues with overheating in hot weather, reliance on mechanical ventilation systems and the possibility of mould issues.

Sid Thoo pointed out that there is nothing currently preventing a Passive House project from achieving compliance with the NCC. He also noted that energy efficiency standards – including Passive House – are like different varieties of apples, “they are all apples, and everyone will have their preference, but this doesn’t necessarily mean the other varieties are inferior.”

This highlights an important point about any green toolkit, which is whether the focus should be on following a specific process such as Passive House for achieving a liveable, efficient and comfortable home or whether there needs to be emphasis on the outcome and the verification of that outcome.

After all, as we know, despite any number of rules and best practice guides and codes and standards, we still have an issue with many buildings achieving the performance metrics the design stage promised. 

In many cases, there is a gap, some of which can be attributed to poor workmanship, poor installation practices, product substitution, or outright failure to ensure materials and methodologies will achieve compliance – flammable cladding on high rise towers being the obvious example of that.

There are also few residential rating tools with widescale adoption that interrogate and report on the actual performance of an individual dwelling across the metrics of energy efficiency, thermal comfort and indoor environment quality.

Passive House, when taken to certification does report on finished product energy use, however, it does not address indoor environment quality in terms of levels of volatile organic compounds, CO2 levels, particulate matter or other health risks. 

It has also been pointed out that the standard does not address embodied energy in construction, nor the toxicity of materials, unlike the Living Building Challenge.

Passive House is “just the first step” – it is not the whole staircase 

Founder of Smart Plus Homes and Passive House design trainer Daniel Kress says that Passive House is “just the first step” – it is not the whole staircase.

He says we can look to Europe to see the likely trajectory of mainstreaming the system’s principles. As of 2020, the standards required by PH in terms of airtightness, insulation and energy performance will be the standard required by EU building codes, he says.

Currently, the Australian NCC is taking “baby steps” in that direction. For example, the air tightness requirements in the 2019 NCC that come into effect in May.

Mould is a rising issue that comes with air tightness

With air tightness will come more issues with mould, he says.

So, a bigger step is required to ensure homes are fully comfortable, efficient and sustainable. He says he prefers to see PH applied like a “spirituality” rather than “a religion” – using what works, and then building on that to achieve the best outcome.

The basic principles of separating the indoor environment from the outside environment to ensure a more moderate and consistent indoor temperature are physics-based. 

This is an important distinction between Passive House and passive solar design.

Passive House is based on physics so this means the tool will deliver suggestions on any refinements needed to achieve the specified energy and thermal performance metrics.

Passive solar on the other hand “relies on the experience of the designer”.

Ventilation for a sealed building is a fundamental health requirement, Kress says.

But even a draughty building will often still deliver “unhealthy air”.

In any building, ensuring ventilation flows requires a pressure difference. For passive solutions such as using windows, it is the thermal difference between indoors and outdoors that creates the pressure differential to stimulate airflows.

In a Passive House, ventilation is not “accidental”, it is controlled and delivered by the mechanical ventilation system, Kress says.

One of the big questions then becomes, what happens if the power goes out during a heat wave?

He suggests opening a window. He also points out that one of the reasons the power goes out during heat waves is the high demand on the grid caused by everyone switching on air conditioning to keep regular, leaky, poorly performing dwellings comfortable.

If more homes met Passive House standards and therefore overall demand was vastly lowered, he suggests such outages would be less likely.

Kress says that considering the embodied energy of a home, including a Passive House home, is important. But overall, the embodied energy is only around 20 per cent of the lifecycle energy footprint – the other 80 per cent is operational.

Overall, as the principles behind Passive House become embedded in the building code, he sees that Passive House associations may have to push the envelope further.

In Europe, the association is losing new certifications at a rapid rate, as the standard’s requirements come into the code

There is need to consider the associations’ “reason for existence”.

If it is to “supply healthy, comfortable homes”, what comes next if that is now a mainstream achievement?

Emerging blockchain, storage and precinct-scale energy solutions might be next

Next steps might be Passive Plus, Energy Smart or even big picture trends such as the integration of emerging blockchain, storage and precinct-scale energy solutions.

The difference between energy availability from renewables such as solar PV during summer and winter is also something to examine.

“Passive House allows overheating in summer to some extent because that is when you have the most [renewable] energy available [for operating cooling],” Kress says.

The challenge is to leverage storage capacity to store excess energy for winter, when PV has fewer generating hours.

The market itself is a problem for Passive House or any other sustainable, energy efficient home approach.

The biggest issue is the perception of houses as an investment rather than a place to live and for kids to grow up in, Kress says.

Consumers make decisions about home purchases based on what will have resale value – so the big house, with the fancy stone benchtops is eye catching because what is being considered is not how comfortable and efficient a home will be to live in, but how easy it will be to sell in a few years’ time.

Kress says buyers often think that energy-efficiency and thermal comfort won’t be selling points when they are ready to flip and move on.

Energy labelling just might make energy efficiency a great selling point for houses

However, given the likelihood of the introduction of mandatory energy-labelling for homes within the next decade, he argues that future buyers will absolutely be more likely to buy the energy efficient and comfortable Passive House compared to a low-rating uncomfortable and inefficient one.

Costs? How about looking at the size of our houses

When it comes to cost concerns maybe the problem isn’t around meeting PH requirements, improving the envelope, or adding insulation and mechanical ventilation, as much as it is about the size of Australian homes.

At an average of 90 square metres for each person, we have the largest homes in the developed world. Around 30 per cent of this is currently “wasted space” – hallways, extra rooms that are too large or too small for any real purpose, front rooms that rarely get used and other rooms that are virtually “big oversized storage areas”.  

“Big doesn’t mean better,” Kress says.

Integrated thinking and banishing bad air

Another view is from founder and managing director of ComfortID, Erwin Boermans.

He wants to see mechanical heating and cooling systems that are air based, such as the standard Passive House heat recovery ventilation system, replaced with water-based systems in the interests of occupant health.

Air-based systems are inefficient and have a tendency to distribute pollutants via dirty ductwork, he says.

In the Netherlands, ducted systems are now banned for the use of thermal energy distribution. This followed major research and advocacy led by Emeritus Professor Annelies van Bronswijk. 

van Bronswijk played an important role to get dirty ducted systems for the use of thermal energy distribution banned in the Netherlands. 

Currently, Australia has the highest energy costs per sq m and the highest asthma rates in the OECD.

A link between the two is the equipment used for heating and cooling our homes, Boermans says.

“Ducted systems are a paradise for bacteria – they make people sick.” 

In the Netherlands, Sweden and other European nations, hydronic systems for heating and cooling are the preference, with pipes carrying heated or cooled water embedded into floors, ceilings or walls.

In Australia, it’s an approach taken by a few, such as the Swinburne University Advanced Manufacturing and Design building in Melbourne, and the Charles Sturt University campus at Thurgoona in regional NSW.

Boermans has a “frustration” with the current Australian picture.

To deliver the “smallest contamination possible” in a Passive House, distributed hydronic heating or cooling is the best way forward. They are also incredibly energy-efficient.

This would need a change in how the early stages of a project are managed. The plumber is currently one of the last trades on site.

The hydronic approach requires integration of the hydraulics during the initial design and build. 

Integrating rainwater capture can take advantage of water’s thermal mass and as part of the heating and cooling solution

It is also possible to go a step further – rather than treating rainwater systems as a bolted on extra, it is possible to integrate rainwater capture and storage as part of the insulation strategy to take advantage of water’s thermal mass and as part of the heating and cooling solution.

Food production can also become part of the equation. Boermans gives the example of a 40-storey tower in Hong Kong where water storage on the roof is used for growing fish for human consumption. The water is also used for fire suppression, heating and cooling and thermal moderation.

We need more integrated design thinking 

More integrated design thinking could deliver building systems not treated as a kit of separate parts but as one holistic working unit. A precinct-scale application of integrated thinking could also help achieve a circular economy.

“The linear economy is slowly dying,” Boermans says.

“And it can work on bigger than one house scale really well.”

How about we don’t fight the weather

Director of Troppo Architects, Phil Harris, says that as humans we cannot control the climate, so ameliorating the climate through the shelter we build is a task of the architect.

However, sealing a building to maintain the indoor climate, maximising insulation and having the airconditioning working is not the only way to achieve comfort.

He points out that we are not living in Antarctica, nor the world’s worst deserts, and by and large our climate is mostly “pretty benign”.

Where we have extremes of temperature our resources could go towards maintaining human adaptability, not weakening it.

In some locations, for example, a farmhouse might have a small protected zone that can be kept warm during severe cold, while in the tropics, a central, shaded and ventilated area is the refuge during heat.

Perhaps we need to “accept weather is a thing” and relish the bonus that comes from “accepting the day that is” and the diversity of seasons. 

Experiences like the cool mornings of summer or the satisfaction that comes from sitting on a verandah at the end of a hot, humid Darwin day.

We need to stay in touch with the weather

Weather becomes a source of conversation and social connection when people experience it.

Harris says it also “puts you in touch with the ecology.”

“If you are not in touch with the climate, how can you understand the environment and curate it?”

Reliance on airconditioning is, after all, a fairly recent phenomenon. 

“Once upon a time it was the most expensive thing you could buy for a house. Like a car was once, it was out of most people’s reach.”

But as airconditioning has become cheaper, more efficient and more refined it has allowed us to “design a minimalist box and add airconditioning.”

This approach is simpler than “designing things that open and close and shade,” Harris says.

It also requires less capital outlay to build the simple box.

To resolve the cost consideration, Harris says we have to be “clever” in design and be “thoughtful and lean” in terms of decisions around interior linings, thermal mass and building materials.

“It takes an effort.”

There are a few key things to consider for designing a good dwelling.

The first is to deal with the sun, he says. Where it will be invited in for cool season warmth, and where it needs to be excluded during the hotter months.

Orientation is a major part of this. 

However, with climate change the degree of heat is higher in months such as September and April, so the standard north-facing solution may not be optimum as sun angles differ in Autumn and Spring.

Devices that provide shade are also part of the equation. There are a “million devices”, Harris says, such as the perennial canvas awnings or the shutters that were popular in 1970s Queensland resort architecture.

Next, a designer needs to “think about the breeze”.

Some winds can be the “enemy” such as the hot northerlies of central Australia, others will relieve heat like Sydney’s onshore breezes.

In the tropics, wind is an occupant’s “greatest friend” as air movement mitigates humidity.

Design development needs to ensure beneficial breezes will pass through a dwelling, not around it. This takes a degree of local knowledge to understand what the prevailing winds are, whether that knowledge is gained from time spent on site or from asking the locals.

Rising heat inside a home can be used positively to create airflow and manage temperatures, Harris says. Heat on the ground floor of a two-storey home from a slow combustion fire, for example, will move upwards and heat second-floor bedrooms.

In the opposite way, hot weather design should aim to ensure rising heat can escape the building.

Rain should be factored in with windows and other openings enabled to continue to work when it rains. 

Thermal mass is another design fundamental, as Harris says “it is the greatest ballast [for a building] in climates that have the greatest diurnal variation.”

There are many forms it can take, including pise or rammed earth, bricks, wattle and daub, seaweed insulation between plasterboard or a concrete slab, for example.

The important thing is thermal mass is a “great conserver of heat”.

“In the tropics you don’t want any at all,” Harris says.

Instead you want materials and a design that will give up any retained daytime heat readily in the evenings.

“In the tropics there is nothing worse than concrete.”

 While Passive House can work in the tropics, ultimately designing and delivering homes is about “what makes a healthy environment” and he questions the degree to which mechanical HVAC systems do this.

“You can’t tell me the sound of whining airconditioning is good for the brain,” he says. “And you can’t tell me pumping heat out to the environment as airconditioning does is good for lowering ambient temperatures in the environment.”

Apartment buildings, for example, create a massive amount of heat in the air around them from the HVAC system air exhausts.

There are also costs associated with relying on mechanical HVAC when the air outside is a “pleasant 26 degrees”. These include the environmental cost of the equipment, the embodied energy in the building, the energy required to operate the HVAC and the ongoing costs of replacing parts.

The current code and its energy requirements is something of a difficulty. Harris says that the energy rating system would give someone living in a tent under a mango tree zero stars – even though their energy footprint is obviously almost nil.

Rammed earth builders also struggle to achieve compliance, even though rammed earth homes are low energy, thermally efficient and have a minimal footprint in terms of materials transport.

Harris points out that post-occupancy research has shown people living in rammed earth homes are happy in their dwelling.

“What is wrong with building happy houses?” he says.

“The NCC energy efficiency provisions take the path of building houses that are unhappy.”

Harris says there are “three things we as humans should be good at – food, sex and shelter.”

“But we have turned that third thing into a consumer item as opposed to learning from our forebears and neighbours. So, we make bad decisions. We go shopping and we don’t know what we are buying.”

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  1. Both approaches to thermal comfort and energy efficiency can work. Passive low energy architecture designed specifically for climate with natural ventilation designed to maximise gains and excellent thermal shells that are airtight to minimise losses with mechanical heating, cooling and ventilation. Both can be modelled with physics though an airtight esky with MVHR is obviously much simpler. NatHERS Regulation Mode is reasonable at assessing the esky model so Passivhaus and project homes have a pathway to approval based on energy allowance. I share Phil Harris’s philosophy around design, thermal comfort, fresh air, health and communication with place and climate. His homes don’t rate well in NatHERS. What all passive low energy architecture needs is an assessment tool that assesses how well a building’s design ensures acceptable levels of adaptive comfort, health and safety rather than thermal shell performance. We are still waiting. Modelling still uses physics and could use the Chenath engine and NatHERS tools though assessment criteria needs to be different. A sailing boat is not assessed on nautical miles per 100l of diesel though it is reasonable that a motor boat is. My 27-year-old PSD mudbrick home rates 3.2-Star and is beyond carbon zero eTool Global LCD performance, 6/6Star NABERS and exports twice as much energy to the grid each year. 2050 target – job done you would think! A current mudbrick project rates 5.4 Star (complies with 1 star bonus from BASIX) with energy loads of 95MJ/M2/Year or 26.4kWh/M2/year which is better than PH Classic criteria for combined heating and cooling(30kWh/m2/yr). Does this seem odd? Am I mistaken? I thought Passivhaus was an aspirational target though it rates 5-Star in my Nowra climate. The newer 5.4-Star home will not need cooling and will be carbon neutral in heating with natural ventilation. Hopefully it will be close to carbon zero LCD though embodied carbon will be up due to good insulation of roof, 1st floor and slab edge plus double glazing. We need to ensure we are not going backwards in terms of full LCD when making small steps forward in space heating/cooling/ventilation. Even if we don’t have operational and embodied energy targets we need to consider them in working up sustainable solutions and in regulatory impact statements.

  2. I would like to contribute re poor council town planning leaving to developers to plan, land, road, and house lots, for lack of sun site orientation. With blocks stacked and councils rate greed allowing smaller narrow road planning. Go to Qld and see how Gold Coast is becoming modern slum development. Passive consumer unknowing and invester nievity. Passive housing what’s that!

  3. With appropriate passive design (refer it is possible to avoid most (but not all) energy used for heating and cooling in those areas of Australians that most of us live. For an excellent example of such a house, which has only ceiling fans (no heating or cooling) see Josh Bryne’s House –

    Passive house (German: Passivhaus) is a rigorous, voluntary standard for energy efficiency in a building, which reduces the building’s ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling. A similar standard, MINERGIE-P, is used in Switzerland.

    Passivhaus design only addresses the energy used in heating and cooling a house.

  4. This article shows the “opinions” of 3 different people that all want the same result, “healthy and sustainable buildings”. I speak of a physical based concept that is internationally proven to work; PASSIVE HOUSE. However, I disagree with some parts of the concept. For example, we should not calculate the air changes per hour we should calculate the permeability of our building envelope.

    I agree on Erwin Boerman’s statement that we could pollute our indoor air if we use the wrong material and systems. However, there is no way that we decrease the air quality if we use a quality heat recovery ventilation [HRV] system with F7 filters and running it for24/7. The ductwork material is usually hospital grade and is antistatic; there is no chance of dust building up and high off-gassing that it reaches toxic levels. I agree as well on the fact that water-based systems can carry more energy, and this could be understood as more effective. This is the reason why we use Air/water heat exchanger to heat the air in cold temperate climates. Passive Houses are that energy efficient that it is possible to use air as the energy carrier, however, if the building is needing more then 10 W/m2 it is not possible to heat the building via the HRV system.

    I agree with Phil Harris statement that we have to live with nature and not against it. As well I agree that our body can adapt to a lot of things. However, I do not think that we should make use of adaptation. 7% of all death in Australia are related to the limited possibility of adapting to low and high temperatures, mainly related to the temperature indoors. Comfort is a health requirement, and our body feels comfortable because it is healthy for us. Comfort, uncomfortable, unhealthy, risk for health, risk for life and finally death zone. If I could choose I would go for comfort. I agree as well that we have to look at a holistic approach and if we want to maintain a planet that is habitable for our kids and grandkids, we have to act now.
    Passive House is not a religion, and it is not able to solve everything, but it is an extremely great tool kit and like that it must be used. If you try to solve hunger with Passive House, it wont worki, but that is not the problem of Passive House. It is using the tool kit. Hundreds of people have developed the Passive House concept over the last 30 years, and I would be a fool to think that I already know everything about Passive House. I do not, even if I am teaching it and work with it for over ten years.
    To all critics of Passive House: the Passive House tool kit is pretty easy. The development of the Passive House tools uses the work of hundreds of geniuses and thousands of helpers. If you want to know how the tools are built, you need to dig deep, and if you then still think Passive House is not working, I would love to know why. Maybe I and the Passive House institute are wrong.

    1. What a great response Daniel… love your even handed openness to challenge and willingness to discuss… our paths to sustainability depend entirely on this attitude and we’ll get there faster if everyone contributes their thoughts in good faith and we assess in good faith.

  5. Great to see an article drawing on three different thoughts on the matter.
    At a Renew event last night (about Life Cycle Analysis), the passive vs Passivhaus discussion came up. Couple of points:
    1. Passivhaus is a misnomer as it uses mechanical equipment to maintain the temperature (probably should be called Active House??).
    2. In Perth, can get a high performing house (little or no heating or cooling) for about $1000 / m2 (using double brick and tin roof). Cost of Active House would be about $3000 / m2.
    3. Active House does not support the indoor / outdoor life style that we enjoy in most of Oz
    4. The operational energy during the life of the house is much greater than during construction of building. An average 40% of operational energy is consumed in heating and cooling. Neither NatHERS nor Active House addresses the remaining 60%. Hence we are discussing 40% and ignoring the larger picture (the 60%).
    For disclosure – I live in Perth in a 9 star house that uses about 3 kWhr day from the grid, and the rest of the energy comes from PV. It is double brick and tin roof and the largest single usage of energy today was the retic pump watering the garden.

  6. It’s not just the Passive House standard. What about a city block with 30 PH’s, all with solar PV and storage, running DC appliances with all unis connected via a DC microgrid. Now you are really talking:-)

  7. I am not convinced passive haus is necessary in much of Australia. Its a big jump in technology which the majority of the industry just cannot climb and does not want to.
    – Improved insulation is necessary – why does Perth love double brick so much?
    – Double glazing – definitely
    – Improved air tightness is a must too. The current build quality is very poor

    The climate is actually very temperate and no heating or cooling is needed for most of the year in Perth. I live inland in a 1970s double brick home with leaky windows. It gets a bit hot a few weeks of the year and it gets very cold for a about 3 months so we need the wood stove on. With better insulation and air tightness it would need much less or no heating.

    What housing needs is properly designed and constructed homes which need minimal or no heating and cooling. It is possible. And its not difficult. However, the industry won’t do this unless they are forced to through additional regulation rather than through flare and innovation.

    The big innovation will be the banks delivering lending products which recognise homes which consume minimal energy. However, as we have seen with the recent Royal Commission, the banks are not very innovative – preferring much lazier and sharper business practice to turn a quick buck.

  8. Great article Phil. I have designed a house that it very comfortable to live in naturally and 80% of the time is between 20 and 26 degrees with no mechanical or electrical vetilation or sealing and is performong at 9 stars yet rated 5.5 stars.

  9. Great article on Phil Harris , I think some people forget how diverse the climate variations are in Australia and imagine one answer fits all – which is not the case at all.