passive house exterior trees, Thornleigh
Sydney's first passive house in Thornleigh

New South Wales now has two Passive House certified buildings. The experience of the designers and builders behind these projects shows that the building standard isn’t easy to follow but it’s worth it to get ultra-low energy homes that are comfortable, quiet and secure.

There’s now a certified Passive House in Thornleigh, on Sydney’s upper north shore, and another in the Blue Mountains.

Airtight construction is at the heart of the Passive House building standard, which was developed in Germany (Passivehaus). This is paired with a reliable mechanical ventilation system with heat recovery, guaranteeing great indoor air quality, ultra-low energy usage (typically less than 80 per cent of the energy used for heating and cooling an average home) and minimal noise penetration from outside. 

Joe Mercieca of Blue Eco Homes, the design and build team behind the Blue Mountains display home, says he “was looking for his next challenge” in sustainable homes, which led him to Passive House.

“It’s sustainability on steroids.”

Mercieca has since skilled up – he’s now a certified passive house tradesman – and had a crack at his first project, the Sapphire Passive House in the Blue Mountains.

It wasn’t easy, he says, especially as the building standard comes up against what’s traditionally taught in carpentry.

For example, carpenters in Australia are generally taught that houses “have to breath” but a passive house needs to be airtight, he says.

The Sapphire home is so tightly sealed that the gaps for air to escape are collectively no larger than the head of a pinkie finger. Mercieca says most of the air is leaking out of keyholes.

It’s also tricky creating a “breathable but non permeable membrane so that water can’t get in but it still breathes”.

He says this is a matter of using the right materials in the right location.

“If you’re not using the materials properly it can make it worse.”

The result is total power consumption per day (without factoring in solar) that’s less than the cost of a takeaway coffee.

The home’s internal temperature is constantly kept at a comfortable level, ranging from 20 to 25 degrees, with minimal reliance on artificial heating or cooling. A ventilation system pushes filtered clean air throughout the house so there’s no carbon dioxide build-up inside.

The house also has a 5.2kW LG solar PV system with battery storage, and is built to the highest Bushfire Attack Level regulations.

Both homes were built using conventional Australian construction techniques.

Peace and quiet

The Thornleigh house is the work of Envirotecture architect Andy Marlow.

“With a third of all our new projects now being delivered to the Passive House standard, Envirotecture are very pleased to see this first project completed and certification received,” Marlow says.

The airtight construction and quality windows will critically shield residents from the noise from busy local roads and nearby train line.

The two-storey home also wraps around a large tallowwood tree that will provide shade in summer.

The house has 10 internal water tanks that help regulate internal temperature. They will act as a room divider while capturing the sun through a huge north facing window that has a retractable shading blind to control the amount of sun during the summer months.

The tanks will be filled after construction and are not connected to the other rainwater tanks, as the temperature of rainwater can be problematically low and pose a condensation risk if put straight into a building.

Although the windows – uPVC with an aluminium external skin – are imported, they come triple glazed as standard, which is more cost effective than a special order of double glazing.

The final result is a home that is 44 times less leaky than the average Australian home.

Passive design can work in Australia

Blue Eco Homes’ Mercieca says the newly certified homes should put to bed any doubts that Passive House isn’t suitable for the Australian climate. This is because the calculations for Passive House are specific to each climate.

“It can be built anywhere… we can build a passive house in Darwin.”

Now he’s done it once, Mercieca expects the next project will be easier. The company has already signed a contract for its next one. 

“We’re very proud to have completed the first Certified Passive House in the Blue Mountains. We hope to build all our future projects this way.”

The certification of these two buildings brings the total number of Passive House Certified buildings in Australia to 18. There is a pipeline of hundreds of Passive House buildings in various stages of planning and construction.

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  1. Well done on the Blue mountains home and the open house. The thermal images showed the consistency of temperature from floor to ceiling. This will change the way we live by showing home owners that its not about the type of insulation but how its installed in conjunction with other material.
    Thank you for the opportunity to be part of the supply of material and the after party.
    Great team.

  2. Graeme

    There is a wealth of peer reviewed research that shows a Passive House delivers better indoor air quality than a naturally ventilated home, primarily because it does not rely on human behaviour except for a 3-6 monthly filter clean (windows need to be opened several times per day).

    You can open your windows in a Passive House. The question is do you HAVE too, only if you want….

    Building physics is the same the world over. Our climate is not totally unique. Membranes and other products have been successfully used elsewhere. Do we really believe we need to reinvent every spoke of the wheel……

  3. @jane
    The house is elevated above the ground as earthworks for a slab would have killed the tallowwood tree. The Building Code requires minimum clearance under lightweight floors hence the steps.
    We (designers) and the clients consciously chose the tree over step-free access.

    Nothing in life is perfect.

  4. Wei and Andy
    Thankyou for the further enlightening information in the highlight of the systems you are advocating to address affordability of housing for the ‘masses,’ as is happening now, using the Australian way by project builders to provide low cost housing.

    However, for Australia these passive houses have a few issues.

    User behaviour it’s been acknowledged as a major issue for building energy efficiency since the mid 90’s.

    The biggest problem that no one wants to reveal, as discussed with my associate, an extremely knowledgeable and internationally “travelled” acclaimed Australian Professor is:

    Even though a mechanical ventilation system with heat recovery, guaranteeing great indoor air quality is used, there is a FILTER which people will not regularly change usually because of cost.

    If filters aren’t changed regularly the ducts and equipment themselves may become contaminated or, no filter change then people are living in a “toxic soup environment” that creates sickness via mould and condensation as researched across the world, and substantiated in the 2018 Parliamentary Inquiry Biotoxin Report.

    Further, when the power grid goes down after dark with no battery backup of solar panels, how do these systems provide conditioned air? Open doors, and windows if possible, then complain about the weather, the power companies and Governments, but at least they get outside air.

    Its interesting office buildings to reduce running costs and provide a healthier environment are now becoming more open plan with plants and natural ventilation, they get awards, yet for housing this push for fully airtightness, high insulated with bulk fibrous insulation buildings and ventilations systems is being “advocated.”

    However, the passive concept has issues as a builder quoted in the 5th estate article
    “It’s also tricky creating a “breathable, but non permeable membrane so that water can get it in but it still breathes”.
    COMMENT These cloth material membranes, I believe the large fibrous bulk insulation companies marketing these products have not substantiated them with Australian testing for Australian conditions to be “fit for purpose.”
    If these membrane products were so good, they surely would be proud to show this. Until the research is independently completed, these material membranes could have the ability to encourage mould and condensation in Australian construction for many reasons that have not be exposed.

    “He says this is a matter of using the right materials in the right location.”

    COMMENT This applies to all materials that interconnect with each other in a building and the tradespeople doing the construction correctly, which is challenging. Do the research and prove once and for all what and where materials should be used for the appropriate climate.

    With the correct levels of bulk fibrous insulation, reflective foil radiant barriers and appropriate airspaces were technically suitable for Australian climates, running costs would be minimal with and healthier homes that would not have to be so dependent on conditioning the internal climate of homes.
    “If you’re not using the materials properly it can make it worse.”
    This statement above:
    I. Is referencing the so-called breathable membranes from overseas.
    II. Membranes mandated by the ABCB without appropriate Australian Research using Dynamic state real house testing.
    III. The ABCB Condensation in Buildings July 2019 Handbook amongst a number of other research papers conducted for the ABCB., which people would be aware of, queries International Standards, for controlling condensation in Australia without further research and testing basically I believe because of our different environmental conditions and building techniques to other parts of the world.

  5. Passive House or Aggressive House? The premise here seems to be designing for the comfort of the occupants with minimal cost for maintaining the home, which is good. The pictures show that universal design was missed out of the design thinking process. Comfort and convenience includes everyone being able to get in and out of the home – occupants and visitors of all ages, abilities and backgrounds. As mentioned in another comment, we are still a long way from building homes that suit people rather than developers and builders. Universal design is not a specialised design – it is for all homes (ref Livable Housing Design Guidelines).

  6. Graeme, I think the answer to your concern is much bigger than Passive House design or any other type of design. Housing commission or whatever form it has taken nowadays has the mission to house as many people as possible as cheaply as possible. This is the result of overwhelming demand and abysmal supply, which are all nearing end of life.

    There’s no reason why Passive house can’t work in a housing scenario from a purely technical standpoint and if it can be mass produced and implemented, it’ll certainly deliver environmental benefits. Issues like leaves clogging gutters and tree roots can all be readily resolved, it’s pretty standard issues with plenty of available solutions.

    The challenge to implement this at scale, and in housing commissions, is not the technology. The challenge is with cost and scale. Unless there’s some legislative requirement or financial incentive or significant political investment in place for high level sustainability to be applied to housing and therefore drive demand to a point where there’s sufficient scale for the market to mass produce these eco homes, drive down cost and achieve the end goal of ‘normalising’ sustainable design.

    It’s pointless to demand the niche private endeavours to solve a systemic and infrastructural problem. If anything, they need to be promoted as much as possible so that the idea of passive house, and other practical ideas and technologies for that matter, can gain wider exposure and acceptance. This would help drive the acceptance and demand for the sustainability industry away from the hobby of a few enthusiasts and into the realm of public / market expectation.

    That’s my $0.02. Welcome any comments and discussion.

  7. Graeme

    In the dense, shaded environment you describe a certified Passive House in Sydney would actually perform very well as it is less sensitive to solar access than a traditional passive solar building. Passive Houses are also ‘easier’ at a larger scale as tehy have less surface area.

    In the UK and North America they are commonly built as social housing(UK) or Build To Rent (US) for their efficiency and low maintenance costs.

    At this moment a Passive House is cost-comparable with a custom home in Sydney (see a paper on the Envirotecture website about that;
    Unsurprisingly they cost more than project homes or ‘standard’ construction but so did cars when they replaced horses.

    This house does not yet have a battery system but does have solar.

    Our intention is to deliver homes that work to as many people as possible. The more that get built, the cheaper they become.

    We used triple glazing in this house, not because we needed it but because the window manufacturer treats double glazing as a special order (and charges more) as they no longer make it. To us this illustrates the power of supply and demand; the price has nothing to do with the actual costs!

    Envirotecture (architect of Thornleigh house)

  8. I read this article well.
    I have a question.
    I’d like to know about the configuration of triple glazed IGU in the passive house in NSW.
    Could you inform me about the email address of the company constructed the passive house in this article?

  9. I am complete shock reading this article. Are the designers seriously suggesting that for the vast variation of Australian climates, that it’s smart, healthy, affordable (and beyond dispute) to build homes totally air tight and never have the chance to throw open the doors and windows and encourage natural ventilation?

    The easy going Australian lifestyle is founded largely on the practice of open living and open windows. I live in Melbourne and for 99% of the year have my windows open – some open slightly during winter, and most open more widely during summer and the intermediate neutral temperatures (i.e. same as indoor and outdoor).

    This is a German concept emanating from the northern hemisphere climates dominated by long cold winter time durations – cold day and night, that Australia does not have.

    When I was in Norway in 1981 triple glazed windows had become mandatory and quadruple glazing was next on the legislative slate. I perfectly understood what I saw because Norway’s winters were so severe and their summer season mild and brief.

    I also instantly thought, well aren’t we fortunate in Australia with our comparative benign winter climates.
    Where the majority of the locations allows people to run around in bare feet for much of the year. Yes, aren’t we lucky. I certainly don’t want to live in an airtight prison where its impossible to feel the breeze run through the house.

    Fair enough if you have the money to do it, like the mansions by the sea in Brighton set on busy noisy Beach Road, which have massively glazed areas and never the hint of an openable window. I shake my head saying, what on earth is evolving? If you face the cleansing sea air, or any rural fresh air location, we intuitively harness natural ventilation aided by rotating ceiling fans.

    The passive design theory appears to be akin to the benefits of temperature moderation as living two metres underground or walking through spectacular caves – which most people have experienced. It seems a highly compelling argument in one sense.

    Well not for me, and not I expect for the cash strapped majority of the public. As for confidently asserting that 100% air tight building design in suitable and affordable for the tropics, I would like to hear what building designers think.

    Submissions for the NCC 2022 Scoping Study are closing 8 September, and its near imoossible (as usual) for the public to decipher its complexities. The juggernaut of sealing of buildings and using blower door testing seems to feature, so the passive house would fit the bill.

    I hope that a torrent of submissions pour in demanding the alternate building design option of the ‘free-running’ house, naturally purged by open windows and the feel of physical air movement over humans and our animal pets.

    What would residents across Pacific think about the air tight Passive Home
    concept? I think we all know the answer.

  10. Look at the photos in the article, space around the house, almost a perfect environment.

    How will this system perform in the housing commission style environment of the project built home estates today, all built on top of each other, mostly tiled roofs dark in colour, hardly any grassed areas, no trees, even low type shrubs, fences and concrete driveways and paths.

    Then additional cost to build these passive house concepts, the average project based housing commission style home (homes that have only a few floor plans with varying colour schemes, basically all look the same) in estates with minimal sized allotments that have issues with ideal room locations to orientation, trees that may disturb or crack the questionable waffle pod slabs, and even if there are trees that lose their leaves in winter will end up causing neighbourhood tension because of the closeness and the falling leaves filling each other’s house spouting, that’s if people ever clean their spouting.

    Of course these passive houses are fantastic, they have battery backup solar power, the average person cannot afford such a luxury, some struggle to attain just solar power.

    How about the Fifth Estate challenge these fantastic passive design associations and builders to build some of these homes in the project house estates, then present their story. Only then, will these concepts be able to claim some sort of credibility.

    I look forward to people reading I believe the truth and comment. Always open to comments.

    Building Energy Consultant., 50 years building experience.