Passive House and the Australian Climate. A Match Made in Heaven?

What sets the Passive House standard apart from other sustainable building practices is its adaptability. Going back to 1991, when the first Passive House was built in Germany, the international applicability of the concept was clear for everyone to see.

After all, what is Passive House other than a rigorous building standard which allows for freedom in terms of the architectural design? As long as the main principles of the Passive House mindset are followed, you can build a structure to adhere to these guidelines anywhere in the world.

Through the use of the Passive House Planning Package, designers can easily change a project according to the needs of the location, building layout, clients’ priorities, and the local climate, of course.

Considering Passive House is slowly but surely gaining traction in Australian building practices, we thought it would be useful to outline the main aspects to consider when it comes to building your very own Passive House. Showing you how to adapt it to the Australian climate is the cherry on top.

The Importance of Building According to Climate

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Building according to the local climate essentially means to ensure the occupants remain thermally comfortable without too much input from auxiliary heating and cooling. This is where a Passive House design shines due to its “work with the climate and not against it” philosophy.

Research has shown the current trend in Australia puts household energy used for heating and cooling close to, if not over, the 40% mark. With proper climate responsive design, this usage can be cut to almost zero.

Even though the Passive House standard puts energy efficiency at its core, not considering the peculiarities of the local climate can have downsides in terms of the building’s energy performance.

There are many aspects of a climate zone that can influence design. For example, a compact building shape with a good ratio of exterior surface to living area is particularly beneficial in very cold and very hot climates for any building.  

The positioning of windows is another aspect that needs to take into consideration the local climate. In the winter season, the low winter sun is a great source of solar gains, and the windows should be facing the equator (why we love north facing windows in Australia).

We can already see that there is no possibility to simply ignore the necessities of the local climate. In the following sections, we will delve deeper into what exactly you should look at when designing your Passive House to suit the Australian climate.

Passive House vs. the Australian Climate

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Generally speaking, there are certain rules to adhere by when building a Passive House in a warm, dry or even tropical climate:

• The design of the house should aim to reduce the heating coming from the outside. Great thing is thermal insulation does not care about the direction of your heat flow, i.e your thermal insulation protects you in the winter as in the summer. Another solution here would be to opt for highly reflective exterior surfaces in combination with cool colours
• Only with sufficient thermal insulation is it possible to guarantee a comfortable indoor environment.
• Solar loads through windows are prevented through the use of a multi layer low E solar protective glazing with a g-value, a solar heat gain coefficient, smaller than 0.5.
• Good airtightness and an efficient heat recovery ventilator should suffice to deal with ventilation loads

Passive House Key Facts per Climate Region

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Out of all climate regions in Australia, Sydney is one region that achieves the Passive House standard with the lowest measures. Because of its mild climate, custom design is easy to achieve.

Melbourne, Adelaide, Canberra, and Hobart are all in tune with the robust Passive House standard focusing on minimising heat losses through the use of the classic five principles:

• Thermal insulation
• Good quality windows
• Heat Recovery Ventilation
• Airtightness
• Lack of thermal bridges

A side note for Canberra and Adelaide would be to stay on top of the solar gain issue in the summer as well. When it comes to Perth, the situation is similar to Sydney.  

Based on the eccentricities of the warmer regions, a different list of Passive House principles has been proposed by the existing research on the matter:

• Glazing – this needs to be done in accordance with the climate and window-to-wall ratio is proposed
• Shading – the use of passive and operable shading is encouraged in order to minimise solar heat gain in the summer
• Building finishes – low solar absorptivity is the name of the game here as this would decrease the solar heat gain in the summer
• Ventilation – the focus here is on efficient, adequately sized, and user controllable ventilation system
• Airtightness – heat flux needs to be kept in check throughout the year

The use of such principles, it is believed, will create a more familiar setting for the designers and builders in the Australian construction industry. This, in turn, should encourage the use of the Passive House standard in warmer climate regions.

It is important to note though that in cooler climates, like Hobart, the standard Passive House principles still do the trick, and are easily adaptable to the requirements of these regions.

The Australian Climate – Passive House Friend or Foe?

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The predominant thinking here would be to say that the Passive House standard is reasonably easy to implement taking into consideration the sheer variety of Australia’s climate regions.

This might also have to do with the fact that the overarching theme is to keep the heat out. This is not a difficult aspect to achieve. Here’s what you need to do:

• Understand the solar loads and ventilation approach so that the inside temperature does not exceed 25 °C
• Optimise the design of the house and give priority to passive cooling strategies so that the cooling load is kept at a minimum

As we mentioned at the beginning of this article, the sheer adaptability of the Passive House standard is its main strength. When you combine this with the main points discussed in this article, there really is no reason to class the Australian climate anything else other than a Passive House friend.

It goes without saying that before you embark on the Passive House adventure, a better understanding of the concept and what it entails is advisable. Luckily, there are a lot of great sources of information out there and we like to think of ourselves as one of them.

If this article has made you less apprehensive of the Passive House idea, we’d love to hear from you.

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