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Whirlybird Guide

Roof Ventilators and Whirlybirds in Your Home

A guide for the curious consumer interested in Roof Ventilation & Whirlybirds

Without a proper means of insulation or ventilation, a standard roof space traps & accumulates heat as the sun beats down onto your roof. This heat radiates down through your ceiling, will warm your home, and accounts for around 25% to 35% of the heat gain in summer, after your windows. Obviously, you can install blinds to block the heat out of windows, but you can’t put blinds over your roof.

When roof heat starts seeping through your ceiling, your home becomes stuffy and hot. Most homeowners will resort to using air conditioning, though unventilated roof spaces will continue to transfer heat. Without a means to keep your home cooler for longer, your power & utility bills can skyrocket.

Methods to ventilate your roof have changed drastically over the past couple of decades. The product most readers are familiar with is the roof whirlybird. One of the first designs for the whirlybird was patented in 1910 by Samuel Ewart. This design in principle hasn’t changed in decades, as it still relies on wind to make the turbine spin. They may also rely on the expansion of air in your roof cavity from rising temperatures.

“Over the last five years I have had two whirlybird units from Bunnings in my ceilings and had, so I thought, done a good job. I later did extensive research and was determined to find an alternative to the whirlybird […]

“The Solar Whiz has now been in for about six months and the temperature difference we have noticed is amazing! On hot days the temperature is about seven degrees cooler upstairs and dramatically cooler downstairs. If I close all the openings in the house and open one window down stairs, I can feel the air being pulled through the window and up the stairs to the top floor.”

Greg Savill

Sydney, NSW


How efficient is a Whirlybird compared to a Solar Whiz?

How does a whirlybird work?

There are typically two types of whirlybirds: your mechanical, active-powered whirlybird, and the conventional wind-driven whirlybird. The far more popular conventional whirlybird operates when the wind hits the turbine fins, causing the vent to rotate. The motion creates a vacuum that sucks air out of the roof space. Unfortunately, a single whirlybird vent will not usually suffice for a modern home, and may require up to four or six units to be installed to feel an effect!

It is worth noting however that they can assist in reducing heat build-up as well as humidity while enhancing air movement in your home. The design is also typically able to resist rain, though it isn’t impervious.

. . .heat radiates down through your ceiling [. . .] and accounts for around 25% to 35% of the heat gain in summer, right next to windows.

Whirly Bird Cooling and Rate of Airflow – Are They Effective?

Depending on what kind of whirlybird manufacturer or model you purchase, each average whirly bird unit is capable of ventilating around 100-150 m³/h in 12 km/h winds individually. Though, naturally, performance will vary from design to design. These factors may range from how warm the air is in your roof space (for air to expand), whirlybird throat size, wind accessibility, and wear & tear in the whirly bird unit itself. Read more about whirlybird models versus other dedicated ventilators here!

In order to feel the effects of ventilation in your home, you might need around 700 m³/h of airflow to keep your roof space near to the ambient temperature outside. Of course, this means you’ll need more than one whirlybird to do the job.

Whirlybird Price & Affordability – Is the Expense Worth it?

A standard whirlybird isn’t terribly expensive. You can pick one up from major hardware stores for as cheap as $60.00 AUD, and sometimes whirlybird installation can be done DIY. However, affordability often comes with a compromise in the modern market, as cheaply built whirlybirds can present design flaws after installation.

Below is a list of downsides that come with purchasing wind-driven whirlybird turbines for roof ventilation:

1) Reliant on Airflow

A whirlybird depends on wind speed to spin the turbine. Quite simply, if there is no wind, it doesn’t spin properly. On an especially windy day a whirlybird vent might ventilate your roof to a degree. However, those dry (or humid) summer days when there is no wind will prove the whirly bird inefficient as your roof space bakes under the sun. In locations where strong winds are common such as valleys, a whirly bird performs as expected. Otherwise, it simply isn’t advised. A powered, mechanical whirly bird might help, but whirlybird price & running costs have proven to be unattractive to the public.

2) Prone to Running Noisily

Cheap roof whirlybirds aren’t necessarily made to run efficiently, or quietly. As the whirly bird operates, the parts rub and can make low squeaking, or grinding noises. The stronger the wind, the more obvious the noise. On top of this, without regular lubrication, the whirly bird bearings can wear or loosen. Worse still, they can make the whirly bird run louder if said bearings are damaged.

3) Inefficient Design

As explained, roof whirlybirds are inexpensive, though inefficient in moving air through your roof space in comparison to other ventilators. Simply, single roof whirlybirds won’t be enough to ventilate your roofspace, and reduce ambient temperature in your home. It would take at least fifteen to twenty residential roof whirlybirds to effectively cool the average-sized Australian home. This many whirlybirds is not only expensive, but ruins the look of the home, as well as makes installation cumbersome & costly.

4) Inclined to Malfunction or Deteriorate

Whirly birds are usually resistant to rain, though their open design can easily catch leaves, dust, or other foreign objects. If enough of this debris enters the whirly bird turbine, it can interfere—and impact the whirlybird performance. Cheaper whirly birds may also rust or can be damaged by severe weather. With maintenance & cleaning, this can be avoided—but are you willing to regularly maintain the fifteen to twenty residential roof whirlybirds needed to keep your home cool?

Solar Whiz – Your Solution for Roof Ventilation

The Solar Whiz is a dedicated self-sufficient solar-powered roof ventilator. Quite simply, it provides you with the efficiency of a powered roof whirlybird without the expensive upkeep or power bills. Given that the Australian climate features near-constant sun exposure when it’s hot, the Solar Whiz runs efficiently throughout the day. It even operates on overcast or rainy days!

Around midday when the sun is directly overhead, your roof space generates the most heat. By around 2 PM or 3 PM, this raw heat will have radiated down into your home. This contributes a large amount of heat to your living space and will continue to do so until your roof space has cooled. Most homeowners rely on air conditioning to keep their living space comfortable. This continued heat radiation will only put more pressure on your cooling to keep up with your needs.

How many Whirlybirds is a single SW-AU-R-40 equivalent to?

SW-AU-R-40 - behind

A single Solar Whiz can perform the legwork of twenty-three residential whirlybirds, reducing the clutter on your roof. They also run quietly and are designed to prevent foreign objects from getting into the fan system. On top of this, the unit can be mounted on many kinds of roofs—from your common suburban tiled roof to metal roofs!

By investing in a permanent, powerful roof ventilation solution like a Solar Whiz, you ensure that your roof space will stay close to the ambient temperature throughout the day. Given that the Australian climate is renowned for its scorching summer, sunlight is in abundance. By using a sturdy design able to resist the worst that Australian weather can throw at it, a dedicated solar roof ventilator is ideal for your roof ventilation needs.

solar roof vents

What about Ventilation for Commercial Properties?

Industrial whirlybirds, on the other hand, with very strong winds operate anywhere from 2,500 to 5,000 m³/h per hour. On average whirly birds need winds of around 8 km/h for a satisfactory performance.

While we provide powerful solar roof ventilation solutions for your home, we also have a commercial ventilation line! We’ve designed them to properly ventilate the extreme heat that large-scale properties can produce. On top of that, our commercial exhaust fans are excellent at ventilating fumes for industrial businesses. Solar Whiz offers one commercial size fan:

  • and the SW-AU-C-155, capable of moving a whopping 10,000 m³/h!

If you plan to buy whirlybird to help ventilate your business, consider a Solar Whiz instead! You’ll be feeling the difference during those hot summer days.

Roof Fans

Dedicated Roof Ventilation – The Practical Choice

The conventional whirlybird is an old workhorse. The aging design has been replaced by far more efficient, dedicated ventilator designs. While they are still produced & used in many Australian homes, more people are turning to solar roof ventilation to meet their home cooling or heat extraction needs. Documented studies have even shown that many of the modern roof ventilator designs cast a shadow over cheap whirly birds.

The Solar Whiz solar-based roof vents are DIY-friendly. It is also free to run during the day (while also having nighttime options). It even comes in a variety of sizes suited to your needs. They can quite easily outperform fifteen to twenty-three residential roof whirlybirds.

The century-old idea of using wind to ventilate a roof space has been dwarfed. Why rely on wind to ventilate your home if the sun is the issue? Use the sun to your own advantage—invest in a solar ventilator to keep your home comfortable this Summer.

Frequently Asked Questions

What is better than a whirlybird?

A Solar Roof Exhaust Vent performs the same function as a whirlybird, but more effectively. It promotes ventilation, which minimises condensation and moisture buildup, which can seriously damage your roof and shingles. Believe it or not, the Solar Whiz can remove as much hot air as 23 whirlybirds.

Are whirlybirds expensive?

A passive whirlybird costs between $60 AUD to $200 AUD on average, whereas an active whirlybird costs between $300 and $500. Remember that these prices are only for the vent and do not include installation charges.

Are whirlybirds noisy?

A functioning whirlybird is almost silent and only makes noise when it is broken. Cheap or improperly installed whirlybirds are frequently prone to this. To avoid this, consult a roofing specialist before making a purchase.

What is the difference between solar and wind whirlybird?
More effective cooling.
Whirlybirds are ineffective in hotter climates with no wind. According to recent tests, Solar Vents can generate the same power as ten Whirlybirds without the need for wind. When compared to Solar Vents, they are not as effective at cooling the property during the summer.

Interested in Solar Roof Ventilation? Click here for a quick, easy, and free quote! Otherwise, contact us on 1300 609 994 today!

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