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Air conditioning versus roller shutters - which is best?

I’m wanting to cool my house down as it gets really hot in summer (WA) but not sure if to choose roller shutters that I know will instantly cool the house down. The outlay is pretty huge but I know my house will be 50% cooler in the hotter months, and will keep winter warmth in. Do I do the whole house or will a few shutters be enough to cool the house down?

Aircon will be great but gives me instant increased power bills as I’ll need it to be on a lot in summer since the house gets really hot and uncomfortable. Then during winter for heating - reverse cycle ducted system is preferred which isn’t cheapest option either.

Which would be better for house resale?

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Welcome to the Choice Community Forum Madhouse :slight_smile:

Insulated roller shutters are great, but they wont cool your house down as such, only prevent it from heating up so much. They’ll greatly reduce heat gain through the windows, but wont have any effect on other sources of heat gain, such as through the roof and ceiling, walls, doors and floor. They do make a great compliment to air conditioning.

Separate smaller air conditioners are significantly more efficient than ducted systems, as they have a higher energy efficiency ratio/coefficient of performance (cooling and heating respectively, but practically the same thing), and if you have installed a PV system that delivers power through most of the day, IE facing E and W, not all to the north, then the cost of heating and cooling can be greatly reduced, and is essentially free in periods when generation meets all the airconditioning demand. A suitably sized and oriented PV system can ensure free AC operation for much of the day, at least when it is sunny.
With modern ACs able to be remote controlled, rooms/areas of the house can be pre-cooled/heated during the day when plenty of solar generation can cover the electrical load- which basically acts as a form of energy storage.

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Thank you Gordon,
Really appreciate you taking time to respond and you’ve helped me understand what I need to do for my home. Now I know how to spend my tax return and don’t need to take a loan or payment plan to do it.

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You may be able to install an evaporative aircon system, aka swampy, as you are in WA.

Our son has one on their home in Perth which was there when they bought it some years ago, and they work great in dry areas like the Pilbara and Alice Springs, and cost much less than refridgerated aircons to run.

You could also install rotary ventilators which will extract hot air out of the roof cavity at no operating cost.

Neither will provide heating but inverter split system reverse cycle aircons will and as @gordon stated, solar power makes the operating costs much less, and if you have a battery as well, you can also run them cheaply at night

We have our lounge room 7.4 kw system on for up to 12 hours a day and our bedroom 3.7 kw system on for up to the same duration.

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Before spending a wodge of cash look at all the options. You haven’t mentioned house insulation which can be a very cost effective improvement retrofitted to your house. There is no point in shading windows if huge amounts of heat comes in through the roof or in running aircon if the house is poorly insulated.

Adding shades will give most bangs for the buck on exposed windows to the east and west where you want to ability to let the sun in during cold weather and keep it out when hot. If you have exposed northern windows (in Oz) a well designed permanent shade like a verandah, pergola or trees may be much cheaper and look better. Adding shades to south facing windows would be much less effective.

Consider also that while windows let in most heat when in sun walls admit heat as well, particularly if the wall is not well insulated. For example, I have an eastern wall with windows that heats up that end of the house in the morning during summer. My solution is to build a pergola that shades the whole wall not just the windows and grow a deciduous vine over it. Shade in summer, sun in winter, low cost, low maintenance and looks good.

There are good free references on the web about passive and active thermal house design, try starting here.

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Oh my goodness Syncretic,

I hadn’t even considered those items. Oh boy I got lots to think about now

Thank you very much for your great suggestions

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Thank you Fred123,

We had Evap air con in previous house. Great until really hot days, but still better than I have now - ie nothing!

Rotary ventilators I’m guessing are the whirlybird things. We have one but I had no idea you can install more.

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The whirly bit is a gimmick. I did some tests on a 25cm unit and found that pretty close to the same amount of air moves through it when holding it from spinning as when it spins. If you have a close look at one, whilst the air makes it spin, it is also collecting air from outside and moving it inside the unit, the opposite of what you want to happen. I made a 3 blade fan from some HDPE and put it on the shaft, which resulted in a noticeable increase in the amount of air exiting the roof space.

Much more effective are the solar powered fans.

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While direct extraction seems better, wouldn’t forcing air into the roof cavity push hot air out of the sofit (or other roof cavity) vents, so they would be much better than nothing? Of course a cursory look around and it seems not all houses have roof cavity vents and depend on huge tolerances around the edges for that function, or am I missing something?

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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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