A shared role between greenhouse screens and roofs is the prevention of heat escape from the roof cavity which allows heat to accumulate and circulate inside your home. This can be quite helpful during the winter season however it can be the source of much discomfort among other problems during hot sunny days when temperatures within the home hit peak levels.
The sun, during warm seasons, can heat the roof to temperatures of up to 70 degrees which is quite extreme. This results in heat penetration through the ceiling and into the house causing great discomfort for anyone inside. It increases the chances of a person developing heat-related illness and exacerbates pre-existing chronic illness including diabetes. To counter this, ventilation and air conditioning longer which leads to increased energy and utility bills.
It is for this reason that highly efficient roof ventilators are needed. During the summer, roof ventilators come in handy as they manage the temperatures in the roof space area contributing to the comfort of members of the household. In the winter time, roof ventilators reduce moisture levels on the roof thereby protecting the roof from deteriorating too easily.
When speaking about roof ventilators, one of the more recognized brands is known as Whirlybird. One of the earliest air-driven roof vents, Whirlybirds have been present and used for several decades. Today we will explore whirlybirds to find out what they are and how they work.
Whirlybirds, also known as Whirligigs, belong to the roof ventilators family responsible for removing heat that is accumulated in the roof space via convection currents.
Whirligigs come in two forms namely passive wind-driven whirlybirds and active, powered whirlybirds. There are differences between these two whirlybirds are many; the chief difference is that the power-driven whirlybirds are electrically powered while wind-driven whirlybirds are run by wind and the continuously increasing in the roof space resulting from rising temperatures. Wind-driven whirlybirds are more popular and many people them as they are inexpensive.
In most cases, the exterior of whirlybirds is made up of aluminum or galvanized steel. The vent comprises of a flute-like head which is set on top of ball bearings, that enables the vent to spin. The outward appearance of a whirlybird resembles that of a turbine which is why you may find people calling it a turbine vent.
The Mechanics Behind How Whirlybirds Work?
Specially engineered fins are located at the metal top of the roof ventilators, and their work is to scoop the wind. This causes the wind to blow through the turbine making the vent rotate. The rotation of the vent creates a vacuum effect which allows the sucking out of the hot air from the roof
In other words, hot air, which normally finds its way to the roof space, is drawn upwards into the whirlybird and expelled to the outside through the vents.
Several whirlybirds working together will help alleviate built-up heat and humidity, in addition to enhancing the flow of air inside the house.
The whirlybird is designed in such a way that it resists rain. When in motion, the whirlybird’s circular force tosses away raindrops like vented air ensuring none of it gets in. Homeowners can rest assured that rainwater will not get in through the roof vent since whirlybirds are designed to be water resistant.
How Effective are Whirlybirds and What’s the Rate of Air Flow?
You can measure the effectiveness of whirlybird roof ventilators by their airflow capacity. That said, there are some factors that can affect airflow capacity such as the make and model of the whirlybird as well as the speed of wind in that locality. The performance of the whirlybird will differ depending on these factors. To illustrate this point, given winds of approximately 12Kph, in the space of one hour, a standard air-powered whirlybird can move around 8-150 cubic meters of air.
During times of strong winds, industrial whirlybirds can move anything between 2,500- 5,000 cubic meters of air per hour.
Satisfactory performance of whirlybirds requires winds of about 8Kph at the very least.
How Affordable Are Whirlybirds?
Whirlybirds are budget friendly with many of them going for less than $100. It is even possible to find some at the price of $60. This is one of the principal reasons why people choose whirlybirds over any other roof ventilation options. The flipside is that this affordability comes at a price. As Whirlybird manufacturers try to keep prices at an affordable range, they have also compromised certain features.
Listed below are some of the downsides you may experience when you purchase an air-driven whirlybird as your roof ventilation option:
- Dependent on Wind Speed. The effectiveness of a whirlybird depends on the speed of wind in your area which essentially means that it will not operate if there is no wind (except the rotation that comes about following the expansion of air in the roof space when the sun heats the roof). This creates a problem in summer when the air is humid, and there is hardly any wind blowing or the speed doesn’t exceed 8Kph. In such instances, only the homes located in windy areas can profit from having a whirlybird- in any other area, wind-driven whirlybirds are not advisable. A natural solution would be to purchase a power-driven roof ventilator (mechanical whirlybird) however power-driven roof ventilators (whirlybirds) lost their appeal ages ago since installation will require the services of an electrician and they consume energy translating to higher energy bills.
- Noise Pollution. The rotation of the turbines makes whirlybirds rather The turbines produce a low grinding or squeaking noise as they spin which they because they rub other parts of the ventilator in the process. When the turbine revolving at high speed or when the winds are really strong, the noise becomes louder. Further, as lubrication dries or when their bearings begin to come loose, whirlybirds may become noisy.
- Low Efficiency. Compared to other roof vents, whirlybirds are not as efficient in moving air out of the roof space which is because the design of the whirlybirds is rather A solitary whirlybird does not have enough capacity to minimize humidity and temperature levels within a home. Studies indicate that the average-sided home requires 10-15 residential whirlybirds to cool it effectively. Picture installing 10 whirlybirds just to cool your home. If you were to purchase one whirlybird at $60, you would spend no less than $600, and this excludes installation fees; not forgetting the noise produced by all ten whirlybirds – it would be the kind of nuisance that gets on everybody’s nerves. At zero resistance, the average whirlybird can move approximately 100cbm while a powered or solar-powered roof ventilator will easily begin at a capacity of 1,000cmb per hour and go as high as 3,000cmb per hour.
- Vulnerable to Malfunctioning. Whirlybirds are uniquely designed to resist rain however they may experience glitches in the event they catch foreign objects such as leaves or other debris. The spinning capacity of the whirlybird will decrease if a foreign object finds its way through the vents and into the turbines. Given the position of the whirlybird (on top of the roof) removing foreign objects is no mean feat. In the event, the turbine becomes damaged, the whole vent will require replacing.
Do Whirlybird Vents Leak?
Turbine vents are like exhaust vents. They have fins which open when the turbines turn in the wind. This turning (spinning) creates suction which draws up the hot and humid attic air to the outside. Turbines usually require little to no maintenance, but that does not mean that problems cannot occur. While turbine vents may leak, it doesn’t necessarily mean that the vent should be replaced.
- Rust or Obstructions
Under normal circumstances, even the slightest of breezes create a force that is strong enough to make the turbine vent spin. The spinning of the turbine causes air to be blown off from the vent, and this force is strong enough to blow away the rain from the openings in between the fins. Rainwater can infiltrate the openings if the vent is rusty since the turbine will be sticking and not moving as it should. Foreign objects near or inside the vent can prevent the turbine from spinning properly. It is important to inspect the vent and rid it of any obstructions. Additionally, replace rusty turbine vents.
- Loose Connections
High winds may cause the turbine vents to pull loose from their standpipes which may result in water penetration. Some turbine vents have their top portion mounted with a friction fit toward the lower standpipe portion. One other way in which water can penetrate is through poor anchoring of the flange that joins the pipe to the sheathing of the roof. Examine your turbine vent to ensure that the top portion (which spins) is firmly attached to the standpipe by sheet metals screws. If the flashing comes loose against the roof, use roofing nails or rust-resistant screws to secure it. Exposed fastener heads should be sealed with roofing cement or silicone caulk.
- Unsealed Joints and Fasteners
At the time of installation, turbine vines will be sealed at various points to avert water penetration. These points include nail heads, the base of the vent, the bead that joins the upper section with the lower section, the point where the flashing and the stack meet as well as the stack’s vertical seams. These points can be sealed off using silicone caulk or roofing cement. Over the course of time, this sealing may deteriorate and require re-application.
- Improper Flashing
If you are experiencing leaks yet your turbine vent is not missing any fins and is in good working condition, then the problem could be at the bottom of the vent. Most vents have a base flashing incorporated that is usually made of metal sheets. These sheets are slipped under the shingles that lie above the vent while overlapping the shingles below. A bent or damaged flashing can let in wind-driven rainwater from below. Rejoin any raised segments of the flashing and seal off all edges and fasteners using roofing cement or caulk. A corroded flashing may possibly have holes in it that let in water and in this case, you should replace the entire vent.
If you would like to go DIY and install a whirlybird on a metal roof on your own, you will save up on the installation cost. Purchasing the wind turbine is the sets you on the path to DIY-ing roof ventilation. In this section will cover how to install a wind turbine on a metal or corrugated iron roof.
You will require the following equipment:
- A ladder to help you access the roof; any other access to the roof can work too
- A drilling machine (battery powered or otherwise) and extension cable
- Marking Pen
- Angle grinder or tin snips that can cut through the thickness of your roof
- Socket to drive tek screws of 5mm (commonly 8mm hex)
- Additional flashing or ridge cap position fitment
Other materials that you will need are
- Tek screws that are 5mm in diameter x 20 long
- Sealing washers to suit
Before you embark on the installation process, it is important to decide on the precise position of the wind turbine(s). Ideally, you should aim to fit the bottom plate of the vent as far as possible under the ridge capping.
Clearly, mark the spot chosen at the base of the ridge cap. Start by removing the fasteners that are holding the ridge cap in place on the spot you want to fit the bottom plates.
Drive in the base plates under the ridge cap being careful to line it up. Mark the spot in which the hole will be cut.
Remove the plate and gingerly cut the hole. You can choose to cut the hole using an angle grinder or the tin snips. The angle grinder will move quicker, but it is noisy and messy.
If you want to use a trim ring, proceed now to fit it underneath the roof. If the trim ring cannot fit through the hole, you can either
- Use a string to lift the trim ring from inside the building or
- Choose a place to cut and feed the trim ring through that hole or lift or lift the trim ring through the using a string. Hold it in place and attach it from the outside (using your Tek screws plus sealing washers). Make sure you are doing this in the trough of the IBR and not the ridges. Use 4 screws for the job.
Install the bottom plate on the rooftop and fasten it in place with Tek screws as well as sealing washers. This should be done on the ridges of your roof sheet and not the trough. Replace all the fasteners that hold your ridge cap in place. Pop rivets can do the job, but they should not be your first choice because they may cause leakage and they cannot bring together the sheets as they are set.
Once you are done, carefully place your whirlybird onto the spigot of the bottom plate
Now it is time to do some spinning. Spin the two halves of the neck at the same time to see how they relate to each other. Next, spin the whole neck and check how it relates to the base plate. Adjust the unit is if necessary to make sure the rotor (LID) stays horizontal. You can opt to make a slight jig to use a spirit level for leveling.
If you are satisfied with what you have done so far, screw in the Tek screws through the openings at the base of the neck as well as the spigot.
The holes in the four securing strips can be fastened using Tek screws.
The DIY whirlybird installation is done. You may now get down from your roof and enjoy up to ten years hassle free operation
Solar Roofing as an Alternative to Roof Ventilation
Solar-powered roof ventilators are a worthy alternative to whirlybirds. Solar-powered ventilators also referred to as solar roof vents are roof ventilators that rely on solar energy. You can install a solar roof fan anywhere on your roof since exposure to the sun is almost constant in most parts of the roof.
You can install a solar roof fan wherever there is sunlight. Solar roofs perform optimally when the sun is shining directly at the top of the roof which is usually the time high-temperature levels are experienced. One more plus for solar roof ventilators is that they run at quiet whisper levels meaning there is no squeaky or grinding noise to be expected. Superior quality solar roof ventilation units such as Solar Whiz roof ventilators possess cutting-edge technology that allows to them operate on quiet whisper levels in full sun.
Compared to whirlybirds, solar roof ventilators are versatile and can be incorporate sleek designs that are less obtrusive and preferred by most people. To add to that, solar roof ventilators have a seamless external structure that prevents the foreign object from entering the roof.
The flipside to solar roof ventilators is that they are more expensive and often their price will be up to five times more than that of whirlybirds. But let’s face it – solar ventilators are a far more superior quality form of roof ventilation in comparison to the cheaper option that does not work as effectively.
The efficiency of solar roof ventilators is not to be underestimated. These ventilators have been shown to work up to 30 times better than the conventional whirlybird ventilators. As a matter of fact, the roof space temperature in a home can be controlled by a solitary solar-powered roof ventilator. In the long run, people find solar roof ventilators a more cost-effective option.
What’s the Best Roof Ventilator Option?
The affordability of the conventional whirlybird roof vents is the main reason why they are preferred by most customers who use the cost per unit approach. Unfortunately, this approach is faulty and does not consider the airflow capacity needed to efficiently and effectively ventilate the roof space. Whirlybirds have clearly been surpassed by several high-tech vents in this day, and they belong to an older generation of roof vents.
The efficiency level of a whirlybird is almost lacking when compared to modern roof vents, and their ability to perform is limited and tied to the drive from winds. Modern-day roof vents are either solar powered or mains powered. An interesting point to note here though is that the solar-powered fans found in the Australian market have a significantly higher airflow capacity compared to mains powered roof fans.
All in all, whirlybirds were good roof ventilators in eons past however technological advances in roof ventilation have overtaken this design have provided more efficient and cost-effective alternatives in the form of powered and solar-powered roof ventilators. As mentioned earlier, even a small home will require a minimum of ten whirlybirds to effectively ventilate roof space. A solar-powered ventilator is a more cost-effective option which is easy to install and does not require the services of an electrician and at the same time, has 10-30 times more capacity than a whirlybird. It also has 2-8 times more airflow capacity than popular powered roof vents.
Whirlybird or Ridge Vent?
Proper ventilation is crucial to the life of your roof. During winter months, attic ventilation is required to prevent the formation of ice dams while in summer, ventilation helps you prevent accumulation of hot air which may result in mold and it also protects the shingles against excessive heat.
Whirlybirds are normally installed on top of roofs, and they rely on wind power to suction hot and humid air from the attic. They comprise of a string of vanes that rotate as the wind passes through them.
Ridge vents, on the other hand, run across the peak of the roof. Ridge vents do not contain any moving parts and are like a screen. They permit heat to escape from the attic.
Installation of a whirlybird is not so expensive because the process only requires removing a section of roof shingles and drilling an appropriately-sized hole to fit in the whirlybird. After which flashing, and sealant are applied around the opening to prevent water from seeping through.
Ridge vents are far more costly option since they run through the length of the roof. Installing the ridge vent system on an existing roof requires cutting away the entire peak. This is what drives up the cost.
Whirlybirds provide more airflow than ridge vents owing to their moving vents. However, in areas that do not experience much wind, turbines may not be the best roof ventilation option.
Ridge vents are passive systems that provide less air movement, and they can work well in moderate climates. Extreme climates will require one or more whirlybirds for proper circulation of air. For a ridge vent to perform optimally, it requires soffit venting which brings air up and pushes it out of the rooftop.
Whichever attic ventilation option you choose, it is vital to have it installed by a licensed and professional roofing contractor. The roofing contractor can also advise you on the best ventilation option for your attic.
Do Whirlybirds Work at Night?
If there is enough wind it will keep a whirlybird going, it will work all day, every day. The same situation will apply if air is continuously expanding in the roof space. There are other questions you should ask yourself – would you want your whirlybird to work all night during the cold season? On a hot and sticky summer evening when there is no breeze, the temperature of your roof will not change. Other roof ventilation systems offer you a night operation option, so it is it important to have this in mind when you make your purchase decision. A daytime effective roof ventilator is good but how good will it be at night when temperatures stand at 30 degrees? You want a ventilation system that works day and night.
Installation Cost of a Whirlybird
Time and cost of installing a whirlybird are generally like what you would spend installation any other type of roof ventilation. Whichever product you purchase, be it a whirlybird or solar ventilation or even a mains-powered extraction fan, you will have to spend money on installation. Installing a whirlybird in a two-story house is more expensive than having it done on a one-story house.
For you to notice a significant difference in roof space temperature, you will need to install 8-10 whirlybirds on the roof. The cost of installing all these units will need to be kept in mind not to mention how your roof is going to look like hosting 8-10 whirlybirds (aesthetics appeal may be lost here). If you choose to go for a higher capacity airflow alternative, i.e. solar ventilation or the powered roof vent, you will only to install one or two units, and that will decrease the installation costs quite significantly.
What Are Whirlybirds Made of?
Whirlybirds can be made of aluminum, stainless steel or galvanized steel. There are pros and cons attached to each material and depending on the shape and size of the whirlybird; the material used will affect its effectiveness, weight, durability, and ease of installation.
Where Should You Place the Whirlybird?
Placement of the whirlybird should be at the peak of the roof because this is the area it will pick up most of the rising heat also t-o receiving maximum wind power to facilitate its operations. It may be a struggle though, installing 8-10 whirlybird units at the uppermost points of your roof. It is likely you will run out of room for your units and must look for other places on the roof to install them, and this may adversely affect their effectiveness.
Air Capacity of a Roof Ventilator
This should be the most crucial consideration when choosing a roof ventilation system. Commercial whirlybirds have a capacity of 2,500 cubic meters hourly while non-commercial whirlybirds range between 100-200 cubic meters every hour. Before making the purchase, you should pity one product against another (i.e., a wind-driven system to a solar-powered system) this way you can compare their capabilities. Irrespective of whether you want a residential or commercial whirlybird, make sure that the product can create a noticeable difference in your roof space.
As you go through the information provided by roof ventilation manufacturers, it is easy to notice the considerable difference between the recommended ventilation capacities of whirlybirds and solar-powered systems. As you compare the air capacities of these two products, you will begin to realize that perhaps not even two or three whirlybirds will bring about a significant difference in roof space temperature for anything larger than a granny flat.
Efficient and effective roof ventilation may not be cheap, but it is worth remembering that you are not in the market for the price rather for value for your money. This means looking at the type of whirlybird or any other roof ventilation product that offers maximum airflow capacity for how much you want to spend. Quality value and not dollar value is the most critical part of your thought process as you choose a whirlybird roof ventilator. Do some research beforehand – you may find spending $100 in exchange for100 cubic meters of airflow per hour not worth the hassle.
How Many Units Will You Need?
The answer to this question will be based on the capacity of the roof ventilator you have chosen to purchase and its cost. You will need 8-10 residential whirlybirds before you notice any difference in the roof space temperature and this should be kept in mind as you look at installation costs unless you want to DIY. Commercial units vary depending on the building and its size.
Residential Roof Ventilation Comparison
Solar ventilation is a powerful alternative to unpowered ambient ventilation. There is a school of thought that claims that it is simply a reinvention of the wheel. Maybe so, but there are tyres that perform outstandingly compared to others!
Solar ventilators can extract huge amounts of air compared to the cheaper whirlybird options that you can find at the hardware store. Passive whirlybird ventilators solely rely on the winds to function while the solar ventilator only needs sunlight to start working. This enables solar ventilators to achieve more than your standard whirlybird.
- Solar Whiz
Solar Whiz offers a broad range of models starting from the small SW-RAF700 to the more powerful SW-RAF2100. The RAF2100 is not the quietest model, but its sheer power makes up for it. Solar Whiz asserts that the air flow capacity measurement for their “Real-Air-Flow” product is based on actual capacity and not theoretical roof capacity which is quite the extraction potential. Adjustable thermostats and nighttime operations are included in the ventilators.
- Solar Star
These units are tidy-looking and come in two clearly distinct forms, i.e. RM1200 and RM1600. These ventilators can extract 1,200 to 1,600m3/h respectively and pride themselves on their noticeably superior power compared to the conventional whirlybirds.
- The Conventional Whirlybird
It is not easy to have an average estimate of either airflow capacity or sound because one whirlybird differs from the other. Our estimates are gathered from the cheap whirlybirds used by many homeowners. Whirlybirds can extract heat and moisture – the problem is that you will need to install anywhere from eight to ten for any temperature difference to be felt and this is in an average home!
Solar Ark offers a range of roof ventilation models, and in this case, we will look at their SolarArk SAV20T model since it is one of their more efficient models for use in a home. Their conventional models are designed in such a way that both PV panels are built into the cap. Theoretically speaking, the SAV20T can extract 2718m3/h. It also has an inbuilt thermostat that gives you more control over the abilities of the ventilator.
- Edmonds Windmaster
The Edmonds’ Windmaster is the go-to roof ventilator for anyone in need of a cost-effective heat extraction solution. This whirlybird is perhaps the most reliable of them all. You can source information about this whirlybird openly because Edmonds has made it accessible to all. Unfortunately, once a whirlybird, always a whirlybird and the Windmaster cannot be relied upon to function effectively on its own. You will need to several Windmaster units to ventilate your property adequately. You can use the Windmaster as your measurement unit to inform the purchase decision for your roof ventilation needs.
- Edmonds Airomatic
This model makes the list of Edmonds’ most robust residential ventilators. This ventilator is not solar-powered instead it runs on mains electricity. Mechanical ventilators do not rely on wind or excessive heat to work; rather they run on electricity thereby providing dedicated ventilation that is capable of extracting heat and moisture. The Airomatic provides enough heat extraction, operates at relatively quiet levels and provides night cooling as well.
- Skydome Powervent
Among Skydome’s products, the SMV300 is one of the lesser known. Skydome is typically known for its skylighting solutions, but they also offer a somewhat powerful mechanical ventilator. Skydome measures heat extraction in liters and they maintain that the SMV300 can expel 15,000 liters of air every minute. Now that sounds like a lot of air being extracted. When converted the 15,000 liters translates to approximately 900m3/h – so in normal language, the SMV300 can extract 900m3/h. This capacity is what has been theoretically stated but not practically proven.
- Solar Bright Maxbreeze
The Maxbreeze is somewhat interesting. There is no comprehensive guide on the extraction potential of the Maxbreeze however you will find a range of optional add-ons. The Maxbreeze’s extraction potential is somewhat arbitrary because it is measured by the angle of your roof and the size of your property.
What’s Best Way to Ventilate an Attic?
The RAVC recommends that the ventilation system in the attic always be balanced. This means equal amounts of
- Intake net free area via vents located in the soffit/overhang or by the roof’s lowest edge
- Exhaust net free is via vents mounted on or the roof’s peak.
This balance allows cool, dry air to come into the attic from the lowest point which in turn helps remove warm and moist air within the attic via the exhaust vents – down the entire base of the roof deck. RAVC member companies have wide-ranging offerings of both intake and exhaust vents.
If the ventilation system in the attic cannot be balanced, i.e. 50% intake and 50% exhaust, then you are better off having more intake than exhaust. It is rather unfortunate that many homes lack proper intake. Having more intake means that any excess intake will automatically become exhausted on the “windless” side of the house since the intake vents located on the windward side will have “pressurized” your attic. What happens next is that the intake vents located on the leeward side will “work hand-in-hand” with the exhaust vents to release air.
If your attic has more exhaust vents than intake vents, there is a likelihood of problems arising. This is because the exhaust vents may end up becoming intake vents to compensate for the imbalance. To illustrate this point using a ridge vent – it is likely that the ridge vent will pull air from the backside if it cannot get air from the intake vents. Similarly, a wind turbine will pull air from another wind turbine located close by on the roof if there is no enough intake to pull from on the roof.
Either way, the exhaust events are forced to ingest air and the weather which is not something they were designed to do.