With 2016 achieving the unenviable title of “world’s hottest year on record” and 2017 already seeing a onslaught of heatwaves in Australia, what are some of the sustainable design features developers might consider to make their buildings more comfortable in this increasingly extreme environment?

SGCH community housing has been built with passive design principles

Ever-increasing property prices have led to developers seeking to build as many dwellings as possible in the fastest time
available. As property prices begin to stabilise and temperatures continue to rise, developers who are considerate of climate sensitive housing will benefit with reduced capital costs, increased habitable floor space and a more marketable product.

Earlier this year, data from the Australian Bureau of Meteorology verified that 2016 was the Australia’s fourth-warmest year on record, while March and autumn as a whole, were the warmest ever for Australian mean temperature. But as our reliance on airconditioning increases, so too does our energy consumption, cost of electricity bills and greenhouse gas emissions.

However, it is possible to exceed compliance benchmarks by going back to basics and employing several passive design initiatives without incurring a premium on project costs:
Building orientation – less space for services means more habitable floor space 

Designing for optimum building orientation in housing is not a new concept, but it’s often overlooked or unappreciated in multi-unit residential developments. Alternate orientations have different seasonal variations and characteristics, specific to location and the associated climate zone. By pairing a room’s functionality with a suitable orientation for the building, we can utilise sunlight and the wind to achieve passive heating and cooling.

Natural ventilation – considered designs save on energy consumption

Another way to achieve passive cooling is to encourage the use of natural ventilation. The strategic placement of windows can produce good cross-ventilation by allowing cool breezes to flow through. A window is often designed to be a fixed element or opens to just 45-50 per cent of its capacity, which limits passive cooling benefits. A wider opening window means greater airflow, which will help to cool down the building.

Glazing and insulation – optimising window-to-wall ratios reduces construction costs 

A trend commonly seen in the latest luxury apartments across Sydney is the inclusion of full floor-to-ceiling height windows across entire facades with minimal if any shading. It’s a less than practical solution for providing adequate thermal comfort to the space. Adding to this is the typical request for clear single glazing. The design may look lavish, but with glazing accounting up to 87 per cent of heat entering a home in summer and 49 per cent escaping in winter, the cost of the facade is anything but affordable. Typically, apartment designs such as these will have high cooling loads that require double glazing or significantly increased amounts of insulation just to meet the minimum compliance requirements, while still leaving the occupant feeling uncomfortable during the hot summer months.

Insulation acts as a barrier to heat flow and is an essential element for passive sustainable design and minimising airconditioning use. Insulation requirements, while mandated for other building types, is not compulsory for residential developments – so long as compliance can be achieved using other design elements. Good building design should pay attention to balancing the wall-to-glazing ratio to reduce solar heat gains and should utilise the benefit of insulation added to the building fabric. Typically, a glazing product will have a higher capital cost than masonry wall material. Optimising the wall-to-glazing ratio will not only help the building to achieve passive heating and cooling but will also reduce construction costs.

Several of Northrop’s clients are actively addressing the need for climate-sensitive urban development. Using smart planning, we improved the building design for SGCH Group ensuring residents would be comfortable for the majority of the year even without airconditioning or heating. SGCH Group was able to enhance the comfort of its residents while yielding significant financial savings.

Nicola Viselli is a sustainability consultant and Erica Chan is a sustainability engineer at Northrop Consulting Engineers.

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    1. Hello Charles, can you please tell me what your experience is with energy efficient homes. Where do you live? Are you interested in getting ‘cool roofs’ and walls recognised in the building code and especially in the ENERGY RATINGS?

  1. ‘A window is often designed to be a fixed element or opens to just 45-50 per cent of its capacity, which limits passive cooling benefits. A wider opening window means greater airflow, which will help to cool down the building.’

    In Victoria you are required to have fall protection to openings above 2m thus openings are limited to 125mm max.

    1. Hi Annon

      [Full disclosure: I work for Breezway, the manufacturers of the Altair Louvre Window]

      There are 3 options to deliver more ventilation through windows while still complying with the BCA requirements for fall prevention:
      1. Use compliant screens to meet the requirements. While they will reduce ventilation to a degree, the opening of the window will not need to be restricted.
      2. Configure the window to have multiple openings. If each opening is restricted, then having more openings will give more ventilation.
      3. Use a louvre window. Restricting the opening of a louvre window reduces the degree to which each blade opens but, with no fixed panes, the entire window area is still opened for ventilation.

      There’s more information on this page of the Breezway website if you’re interested.

  2. When you quote 87% of heat ingress via windows, I wonder if you have a percentage heat ingress via the dark walls in the top photo? My medium coloured bricks get very hot on the western wall and the heat can be felt on the inside for some hours after sunset.
    Also I have met people who live in white walled and white roofed houses who say they rarely have to use any aircon. Why is colour not a factor in passive solar design for high performing houses as reported in this article? Light colours reduce solar heat gain by a huge percentage. I have a medium coloured terracotta tiled roof, which gets to 55C in the roof space. By replacing the blow in insulation, with R5 EarthWool I have achieved a 10 degree reduction in internal temperatures, from 37C to 27C. This is a huge benefit and I am so happy with the improved thermal performance for minimal cost. The Roof is exposed to the sun all day, up to 14 hours. Whereas the eastern and western walls are only exposed for less than half the summer solar time, ie a few hours.