At least I can not focus on that too much then as it’s only another cost, Thank you again Gordon
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This also applies to airconditioning. Not insulating means significantly higher running costs and increased risk of condensation and mould growth.
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Convection forces the hottest air to the top, where the extraction should be done. Attempting to shift it out other lower down orifices is not very efficient, and wont remove the hottest air.
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If you can create a big enough opening near the high point of the roof then convection works really well.
I put a custom vent in my roof along with some other changes described here. The fan was never installed as natural pressure is enough.
https://www.renovateforum.com/f193/roof-space-project-94156/
Also, in Perth, over summer there is often opportunity to use cooler evenings to cool the house and close it up in the morning to minimise AC requirements . So if you can create opportunity for airflow through the dwelling overnight without compromising security it is beneficial as part of a heat management strategy.
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Oh and BTW in Perth we put shutters on windows facing west, summer afternoons when they are closed they have a very positve effect on comfort, and they are also very effective in winter at reducing heat loss being closed after late afternoon till morning.
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A little of topic but some info on effectiveness of foil under tiles.
https://www.renovateforum.com/f193/foil-under-tiles-94013/
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Hi Madhouse, All the above suggestions are good. I also recommend a system called VENTIS in conjuntion with other methods to reduce heat gain (double-glazed windows, curtains and deep eaves / roof over exposed windows plus trees to shade windows) and some airconditioning. I have VENTIS, airconditioning and double-glazed windows in my house which work wonders (but all together cost about $45,000 the retro-fitted double-glazed windows cost $32,000). VENTIS is a sytem that cools the house in the evening / night. When the outside air has cooled to be less than inside temperature then air is pumped into the house pump and filter in the roof space, and warm air in the roof space is vented out. In the winter, warm air from the roof space is filtered and pumped into the house during the day. It is very cheap to run (approx $100 per year electricity + yearly service / filter clean). I use it in conjunction with the A/C. Each covers half the day therefore A/C only working half time and this reduces cost.
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Wow, thank you all so much for all this fantastic information. A lot of things I wasn’t aware of and others I hadn’t taken into consideration. Definitely need to bide my time to research it all and work out what will be my better options. Thank you
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I have lived in a number of homes in both NSW and Tasmania (and yes it does get hot in Tassie!). Double glazed windows make a difference as does any type of air extraction system. You can get an automated whirly bird with a thermostat so that when the roof cavity space gets to say 21 degrees it will start to pull the hot air outside. It must be mounted at the highest point to be effective and you need vents like ducted air con strategically placed but a professional installer will do this for you. I also had a manual override switch installed and used it like a giant exhaust fan to to freshen all the air in the house! Combine that with good insulation, blinds or curtains and air con set to a constant temperature (the biggest $$$ are from the system suddenly starting up to cool down or heat up) and cleaning the filters. Do lots of research first and good luck!
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A few have mentioned double glazing as part of the way to save, a great option if you can afford to do it. Better to do it as part of the build of a house as it will be cheaper than retro fitting it after a house has been built. If you can’t afford it or rent then the next best option is to fit heavy and if possible blockout curtains to windows. This reduces the amount of solar energy entering a room/house and helps reduce cooling costs. You can also try to reduce the impact by fitting solar film to windows as this can help reduce the solar radiation entering.
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UK use double glazing. It’s not so common over here but is really effective for management of heat flow
Solar film a new one to me so definitely got more research. Glad I haven’t rushed into my decisions
Thank you c-j-smith and grahroll
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Also consider honeycomb (aka cellular) blinds.
Insulated cellular shades are typically considered to have the highest R-values of all window coverings.
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Spot on, double or even triple glazing is used in Europe, North America, Japan. Any where it gets really cold and there are rich economies.
The benefit in reducing energy transfer across a window increases as the difference, inside vs outside temperature increases. For most of Australia the differences between comfort and the other side are for most of the year not that great. A half or a third of what Northern Europe experiences. There are other more cost effective solutions that provide a greater relative benefit.
Note Australia’s supply and distribution chains are not very efficient. Products such as double glazing appear to be priced with a luxury premium at around 50-100% above typical costs for a British home, if Grand Designs is a guide.
To get the maximum benefit from double glazing, the rest of the building needs to be well designed and insulated. For Australia this includes importantly shading windows and walls from hot sun. Double glazing does not keep our radiant heat from direct sunshine. Large north facing windows may be great for winter mornings, but they are solar heat traps for summer, hence comments by @grahroll and others on how to reduce the impact. Most of the heat transfer in an Aussie designed house comes through the roof/ceiling, walls, floor, and air movement. The windows can have a significant effect if there are many of them. Think walls of glass louvres or 6m opening patio doors. It then, are not these intended to let the great outdoors in anyway.
P.s. properly fitted external or internal shutters can also be effective in managing heat losses from windows, and may be easier to retrofit than double glazing, for our less severe climate. Keeping direct summer sunlight off the windows and near walls with shade hoods, external screen panels, etc may be just as effective and less expensive for some?
Australia house design has IMHO delivered some of the most ghastly, energy wasteful designs all on the say so of a bunch of stuck up style gurus. They put environment a distant last, not first. Time they retired!
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I got a replacement/retrofit double glazing quote not too many years ago and the payback time, prior to installing solar and having $150 pcm electric bills was well over a century no matter how computed. Now that my average power bill is under $40 pcm, with the same cost to install it would simplistically be triple the payback. I have more and larger windows than most, but. The payback is computed against the cost and best case savings from the insulation differences.
New construction is different economics. How many of us would/could retrofit just because it would add some comfort to the interior, or just because they felt it was the right thing to do?
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Yes, in Melbourne in a 1960 midcentury timber home, we grew vegetation to shade on the east and west, plus some to north. The eaves were wide, properly architect designed to shade and had ceiling insulation…
So the house was much cooler than expected, no window coverings either.
On selling the Asian buyer cleared all vegetation and it was very hot and much glare.
In Perth fast brewing fruiting vines and perfumed would be good on a pergola for a start.
I would will consider blown in rock wool for walls if I buy another timber house,
IKEA sells a range of translucent insulating white interior blinds …have a double layer with air pocket and cheap.
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I think you’ll find that our profit extraction from supply and distribution is unsurpassed! 
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Can’t help you, I’m afraid. We don’t have a problem with just overhead fans and open windows. No air conditioning. We did add a full-length shady verandah, part insect-screened, to the back of the house many years ago. We do have overhead fans on the dining area of the verandah as well. If all of the windows in the house were louvres (instead of just the main bedroom), it would be even better.
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Of course there is a point in shading windows. Each square metre of window, in full morning or afternoon sun, can ad close to a kilowatt to the house’s cooling load.
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If that is what you are saying, I did not and do not advocate against shading windows - quite the opposite.
The OP had framed their question in terms of shading windows or aircon. I am saying look at the whole thing and decide which actions will give the best result per dollar spent in your case and do not focus on just the windows.
How would I be telling people not to shade their windows and in the next paragraph go on to describe ways to do it?
Air con would be my choice
