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Hi all .
i have just about finished renovating . But can't live in it .It's to bloody hot with the new colour bond roof .How effective are whirly birds at reducing the temp of the roof space . which should result in reducing the temp of the house ? And how many are normally needed ?
Also are evap aircons any good and does having a colourbond roof effect them differently to tiles ?
thanks
Rob
In my experience whirlybirds are effective only if you have enough of them and if they have soffit vents to help the airflow. We had two and not much effect, three were better, but when the soffit vents went in they took off. There are websites that tell you how many to get for the roof size you have.
Can't help you with the evap cooler. They work well in Melbourne but someone in your locality might have local knowledge for you.
I have a 10 year old "whole of house" evaporative system (ES). I can't remember who installed it. The system has been maintenance free over the 10 years.
In terms of performance, an ES is very effective in Perth's dry heat but degrades when it is humid (but then again, Perth doesn't have many humid days). In very humid weather, I rely on over head fans and pedestal fans. It is almost mandatory that you have ceiling insulation no matter which cooling system that you adopt.
On Boxing Day 07 the temperature hit 44.2C but inside my house it was a comfortable 25C (that's at about 50% of the system's capacity).
Running costs are apparently 4-6 cents/hour.
An ES is about 75% cheaper then a refrigerated system (installation and running costs).
The system is plumbed directly into your water mains. Periodically, the system automatically replaces the water in the system's sump (installed on your roof) and discharges the old water. This is done as a safety measure to ensure that stagnant water is periodically replaced. I have no idea what effect this replacement has on my water bill.
HTH
Mike
Like Groggy I had good results with rotary ventilators; installed 3 and the house is about 18 sq.
That said, the whole solution will involve aspects of insulation too but I'm sure you know that.
The insulation strategy has to suit your climate and will vary around Australia. Do a search on posts if you need more info; somewhere there's a good Vic govt website (IIRC) outlining what to do where.
I should add that before the whirly's went in you could feel the heat pushing down from the roof. I haven't felt that since installing them, even on 40 deg + days.
My parents have ducted evap cooling. It works great in dry heat conditions which is what Adelaide and Perth gets most of the time. The running costs are also very low compared to refridgerated cooling.
Evap cooling doesn't work well in humid area (Sydney and above)
I also have family in Alice Springs. When they built their house (colourbond roof) they put in evap cooling and a couple of reverse cycle split systems. After a few years they ended up getting ducted refridgerated cooling through the whole house to cope with occassional bursts of tropical weather coming down from the top end.
Is your ceiling insulated? Insulation will go a long way in reducing the radiant heat from a colourbond roof.
I have an evap aircon in Perth. I got a company to quote for a 6 outlet and then I doubled the power of the model they quoted for. Everyone advised me not to do it but I think it's the only way to get an evap that REALLY works. I've lived in houses with not so powerful evaps and you have to crank them all the way up to get them to work and then not so great.
My over-sized unit I only need to have going on 2 (out of 10 speeds)
A summers night is spend asleep under the doona...
Quote:
Originally Posted by jags
See http://www.greenhouse.gov.au/yourhom...ical/index.htm
for info about your problem.
Ceiling insulation 1st at the highest R value you can afford - R4 or R5 in WA. Most evidence is that whirlybirds are useless except when installed in large numbers and with proper vents to allow sufficient airflow - and the volume of flow needed to make a difference would amaze you.
Evap A/C works well for the most part in southern parts of WA. Not effective at all in humid climates and as they use moisture to reduce ambient temperature by around 7-10 degrees so if the outside temperature gets above about 40 then you will still feel pretty uncomfortable inside.
Refrigerated is effective but expensive to run - and will be more so with inevitable rising energy costs.
It is important to look at your local observations from the weather bureau and local av. min and max temps - install to deal with the most common and likely temps and conditions rather than occasional peaks and extremes.
Ceiling fans are very effective and cheap inside and awnings and good tree plantings or climbers on suitable structures can effectively reduce sun falling on the external walls and windows of the house - not letting the heat in in the first place is the best option.
The above site covers all those issues.
I installed these for a while for edmonds.
For each whirly bird or supavent you need 4 under eaves vents to help replace the air. I have a colorbond roof myself with 2 supavents and 8 under eaves, it works a treat. obviously there are days when the only air to replace the hot exhausted air, is bloody hot .
They also sell flexible ducting and open/closeable ceiling vents if you had a certain hot room to connect straight to the whirlybird. but I only fitted one so I didnt get any feedback.
If you are looking at the same whirlybird, look at the supavent, used to be a similliar price but its guaranteed to work 50% better in low wind.
Regards
Davo
When you say under eave vents, you mean these?.Quote:
Originally Posted by davo2310
The eaves on our house have a perforated board that runs the length of each eave, I presume this is to serve the same purpose, therefore do I need under eave vents?.
Cheers,
Aaron
G'day Aaron, doesnt sound like you do, as long as you have fresh air to replace the exhausted air.