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Whirlybirds vs Solar Powered Ventilators – P1

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Whirlybirds or wind driven fans have been around forever, but lately there has been a lot of discussion about solar powered roof ventilators.

So, what is all the hype over solar fans about?

Basically, it’s about how much more powerful solar-powered roof ventilators are, compared to the classic whirlybird.

The average domestic whirlybird moves around 100 cbm/h – at around 12 km/h wind speed. It is hard to find this kind of data from the manufacturers of the wind-driven fans – but there seems to be a consensus when surveying the different solar-powered roof ventilation fan options that they are equivalent to 10 to 30 whirlybirds.

This is also in line with data published a while back after a conference at the Queensland University of technology by Shane West, from University of Technology, Sydney.

The only wind-driven fans with capacities comparable to solar roof ventilation fans are industrial whirlybirds, which come in a variety of sizes and capacities – but once again – it is hard to find data.

In Australia – the most well-known Industrial type is the Edmonds branded 900 mm Hurricane with a capacity of 2700 cbm/h at 12 km/h wind speed and 3400 cbm/h at 16 km/h. The problem is of course that they rely on the wind – and it may not be windy on the hot days when roof ventilation is needed the most.

solar-powered roof fans

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At the moment it is most unusual to see industrial whirlybirds used on homes – and even offices, daycare institutions, retirement villages etc. – you only see these very large units used for industrial ventilation of warehouses and ventilation of factories.

However, if you are looking for wind-driven roof ventilation matching the solar ventilation alternatives – you need to look at the large industrial whirlybird varieties which aren’t generally found in hardware stores like Bunnings or Mitre10.