Thinking about renovating or retrofitting? Here's the things to consider to keep your home energy-efficient.
Renovating or retrofitting? The energy efficient Big Small House in Palm Cove by POD (People Oriented Design). Image Nic Granleese.

Renovating or retrofitting? Take inspiration from the energy-efficient Big Small House in Palm Cove by POD (People Oriented Design). Image Nic Granleese.

A person’s home is their castle. And just like Darryl Kerrigan, we want our homes to be comfortable, healthy, sustainable, inviting and inexpensive to run. So how do we get there? And what can we gain from renovating or retrofitting?

We asked the Research Lead of our Building Simulation, Assessment and Communication team, Anthony Wright, for tips on energy-efficient home improvements.

Back to the future: Retrofitting your home

Your house doesn’t need to be new to be energy efficient. You can retrofit your house, and get results, with minimal cost. Here’s how:

Choose and use your appliances wisely

Buying energy-efficient appliances is a good place to start. You’ve probably seen the energy rating stickers on fridges, washing machines and other appliances. The ‘star rating’ lets you know how energy-efficient the appliance is. You can search for highly-rated appliances and find out how much you’ll save on power bills.

We spend a lot of money on air con. Try turning on a fan to work with (or instead of) your air con, to provide a cooling breeze. It can make a huge difference. Fans are less energy-intensive and expensive. A ceiling or pedestal fan can use just 10 per cent of the energy of an air conditioning unit for the same room.

Install solar photovoltaic (PV) panels

More than two million Australian homes now have solar panels on their roofs. As panels become cheaper, more Australians are choosing to install them and reduce their bills and carbon emissions. Homes rated at eight stars and above can often generate all their own power from a standard six-kilowatt solar array over a year, and you can sell anything extra back to the grid.

Throw some shade

Plants can shade windows and cool your house. If you plant deciduous species, they’ll shade your house in summer, and allow sunlight in to warm your house when their leaves have dropped off in winter. If you don’t have a green thumb, don’t worry! Blinds, curtains, drapes and external awnings all help to keep heat out of your home in summer. Heavy drapes or external blinds can be one of the most cost-effective ways to keep your home warm in winter and cool in summer.

Seal, glaze and insulate

Australian homes are notoriously leaky. We waste a lot of energy cooling air in summer (or warming it in winter) only to let it all escape outside. You can install window and door seals easily in most older houses, by yourself. Hardware shops can tell you what you need to do. You can also install chimney dampers, replace exhaust fans with self-closing fans, seal up old wall vents and install covers on your evaporative cooling vents during winter.

Wherever you have removed the plasterboard or wall cladding, remember to install insulation. You might only be renovating the kitchen, but if the plaster comes off those walls, it might be a once-in-a-decade opportunity to install some insulation. While you have builders on-site you can also ask them to install ceiling or underfloor insulation or top it up if your existing insulation has compressed over time.

We lose 10-35 per cent of heat gains or losses through single glazed windows and doors. Retrofitting your house with double or triple-glazed windows and doors will make your house far more comfortable in extreme weather. It will also save you money and make your home quieter, as they block outside noise.

Don’t neglect the small stuff

Ask your plumber to install your new hot water service as close to taps as possible. Ask them to ‘lag’ the pipework (this is special piping insulation) with extra-thick lagging (25mm is good). You’d be surprised how much energy is wasted transporting hot water around in uninsulated copper pipes. Ask your builder to use any leftover insulation batts around the bath when they install the bath hob. It will keep the bath toasty for longer.

If you’re rewiring, make sure all your new lights use LED lamps and get a quote to install solar panels at the same time. Make sure any new windows you install have a low U value and that they open to catch the breeze. Think about external shading and internal drapes.

But it’s not just homeowners that can live in energy-efficient spaces. Canberra and Victoria have recently announced minimum energy efficiency standards for rental properties. All renters can use these tips to help stay comfortable.

  • Seal drafts wherever you can. You can do this by using door snakes. Ask your landlord if you can install door seals or hanging temporary curtains to zone rooms. Better Renting in Canberra has a great guide.
  • If appliances need replacing, ask your landlord to consider choosing high star-rated appliances.
  • Keep an eye out for solar schemes for renters, like this offer by Solar Victoria.
A woman sitting in front of large windows in her home. When renovating or retrofitting ventilation is an important point to consider.

The upcoming webinar (see details below) will feature Jenny Edwards, whose company, LightHouse, won the 2018 Master Builders Association Sustainable Construction Award with this Vasey House renovation. Photographer: Ben Wrigley.

Grab your hard hat: Choosing to renovate

Leaning on the renovation side of renovating or retrofitting? Renovating your house is a chance to change all the things that don’t work. Do your windows all face south? Maybe you can effectively turn the house around with new northern glazing. Does cold air flood the house every time someone opens the front door? Maybe you can add some internal doors to improve the zoning. No matter what you are altering, thinking about the basics early in the design process means your house will be more comfortable and keep your energy bills low.

Open up to orientation

The orientation of your home can have a big impact on your energy efficiency. Consider potential changes to let more sun in winter or keep it out in summer. This can cost nothing more than taking some extra care in design.

Take advantage of natural ventilation

Make sure your windows are placed to take advantage of cooling breezes and are WERS rated to keep you warm in winter and cool in summer.

Maximise insulation

This is one of the best investments you can make in the energy efficiency of a new or renovated home. If you’re adding, removing or altering walls, you have a once-in-a-lifetime opportunity to max out your insulation. You’ll probably never get a second chance to maximise the insulation of the new parts of your construction.

Consider thermal mass

Heavyweight materials like slab and brick can help to even out internal temperatures. A good designer or energy rater will be able to help you decide.

Get an energy rating early

Before you get started it’s important to know what you’re working with. Find out what your house will rate before and after your renovation and ask your designer if that is the best they can do. It is possible to bring an old leaky house up to modern standards with the right renovation.

Want to know more? Here are some resources to help you out:

Watch our 10 tips for keeping your home warm this winter.


  1. Would love some information about how to increase air flow in the roof cavity or to expel it through there. We have a 2 storey home, and while we can open windows etc once the outside temperature drops, it takes a long time to disperse the heat. Wondering what I can retrofit to help with this, Thanks

    1. Hi Frances,

      Thanks for your comment. We reached out to Senior Experimental Science, Michael Ambrose, who has provided this answer to your question:

      Increasing air flow through the roof cavity will indeed help to lower its temperature. Roof cavities can get to very high temperatures, up to 60 degrees Celsius in some climates. However, the amount of this heat that transfers to roof spaces below is often dependent on the amount and quality of insulation that is installed on the ceiling.

      Insulation with a high R-Value that covers the entire ceiling area (no gaps around downlights, access holes, duct registers, etc.) will greatly reduce the heat flow from the roof cavity to the rooms below. In two storey houses often the reason that the upper floor is hotter than the ground floor is from heat that is rising up from the ground floor and getting trapped on the upper floor. Remember heat rises! So increasing cross ventilation in the upper floor rooms will help shed this heat. If a roof space is poorly insulated, then heat has the potential to radiate to the rooms below.

      You can increase ventilation in the roof cavity by allowing cross ventilation to occur in the roof space. This is easier in some roofs than others. A simple gable roof can have vents placed at each gable end and this will dramatically increase ventilation. If you have a pitched roof, this is usually not possible.

      A common solution is to install whirlybirds. These spin when there is a wind and suck air out from the roof space. They are relatively cheap and easy to install. However, there are a few disadvantages to these. Firstly they do of course need a breeze to work. On a hot dry and still day, they will not do anything. Also, for them to be effective you actually need quite a few. Installing just one will usually not be able to move the volumes of air required to actually cool the roof space.

      Another option is solar vents. These are fan units that are installed onto the roof and have a small solar panel on the top that powers a fan unit that extracts the hot air. Most have a thermostat that controls when the fan comes on and some even have batteries so that they can continue to operate after the sun has set. They are generally able to move much greater volumes of air than a whirlybird will, so often only a single one is required.

      We hope this helps answer your question! Best of luck with any changes to your home.

      Team CSIRO

  2. Marvellous article.

  3. I wonder if the managers of this comment box can please get a scientific and professional response for me.
    Whilst there is a lot of useful information in the CSIRO tips for EE, one simple yet very cost effective design principle is missing. In my experience I have found the coolest houses; the ones that require the least air conditioning, are those with white roofs. I wonder if the CSIRO has considered this element in house design in your research.
    There is not one mention of roof colour or solar heat gain through the roof. Only Insulation is recommended for ceiling spaces.
    However, in your reference to the YourHome website “Choose light coloured roof materials.” – is mentioned 6 times.
    I believe this needs to be a strong point made to the public, and in the renovation and retrofitting business, as what I see in many older houses in my area Climate Zone 3, most roof renovations are black.
    Roof restoration in Perth is big business with lots of companies offering this service.
    Also many of the new areas in Perth are characterised by a combination of white and dark roofs, looks like salt and pepper. This demonstrates that those who know the EE and thermal comfort levels provided by colour choose white and those who don’t choose black /dark. Also these new areas are fence to fence housing with no room for your suggested plants and tree cover.
    A suggested “fly cover” would be unnecessary with white roofs.
    BlueScope has done excellent research on colour and applied Solar Absorptance ratings to each colour. White being SA 0.18 and black being SA0.98. The tile industry seems to be using the same data.
    Sadly, the roofing companies offer few light colours (and exclude white except in the commercial colours) and almost exclusively advertise dark roofs.
    BlueScope have fortunately even suggested that solar PV will be more efficient on a light roof. They have published a study where commercial businesses will save significantly on energy costs with white roofs.
    The Switch Your Thinking Program at the City of Gosnells, WA, conducted their own research also concluding the benefits of Cool Roofs.
    With rising temperatures and more day time temperatures over 30C for 8 months of the year (Perth), something has to be done to reduce the UIHE, energy use and energy costs; green house gas emissions and climate change.
    The ABCB (Pitt&Sherry) says households can save 18% and businesses 53% in energy costs. EnergyCut says Australian businesses can save $1b each year with white roofs.
    As a white roof costs Nil, it should be stressed in the CSIRO ‘top tips’.
    As a forefront research facility supported by the tax payers of Australia, the CSIRO must be more forthright. Australians are counting on you to provide strong scientific evidence to benefit all residents and protect the environment for future generations.
    through large energy savings,
    Australians will individually be more wealthy / less financially stressed.
    I can’t stress enough how urgent this matter is.
    0414 589 188

    1. Hi Joan, thank you for your question. Here is the response from Michael Ambrose, Senior Experimental Scientist and former architect.

      “We have looked into the benefits of light coloured roofs and we get a few different outcomes depending on location. In the cooling dominated climate zones (like Perth where you’re writing from), then yes light colour roofs are beneficial. However, the modelling has shown that in heating dominated climates (like Melbourne and Hobart), the darker roofs can actually perform better because they do absorb more heat during winter that helps keep the house warm. Of course, the reverse is also true that in summer in these climates then the dark roof will continue to heat the roof space and potentially cause additional heating to the rooms below.

      One aspect that our modelling does not take account of and that I keep thinking may be an important factor is that as the roof space heats up this will impact on ductwork that is in the roof space. For example, many homes have ducted air conditioning or ducted evaporative cooling. Ductwork does have some insulation around it, but it is not very thick so probably does not provide a great barrier to the heat of the roof. I am not aware of any research that has been done to look at this issue. Light coloured roofs would help to reduce the heat impact on the ductwork.

      Certainly when building, roof colour should be taken into account and as noted, the choice a roof colour is usually cost neutral. When renovating however there may be other factors that people consider. If you are reroofing the entire house, then no problem in selecting the colour. If you are only roofing a part of the house, you may want to match the colour to existing roof colours. Another issue is that in some housing estates and even some council areas, they can dictate the roof colours that you are allowed, all part of the “aesthetics” of the area.

      My inclination is that on balance lighter coloured roofs are the way to go, even though our modelling in climates like Melbourne and Hobart do not reflect this. Also, the impact that hot roof spaces can have on ductwork is something that needs consideration and probably some research!”

      Team CSIRO

  4. Bravo – this is real architecture and design.

  5. Wonderful tips on energy-efficient retrofittings and renovation. Installing solar panels,insulation and blinds are great addition to the checklist.

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