Ventilation and insulation are important factors you should always consider for your roof. Without these, your roof will trap a lot of heat during the day. By accumulating a lot of heat, your home will become hotter than it’s supposed to be, especially during the summer. Through radiation, the excess heat warms your home, leading to a heat gain of up to 35%. This is almost the same as the amount of heat gain your windows allow in. Fortunately for the windows, you can simply install blinds. However, you cannot install blinds over the roof.
Your home becomes hot and stuffy as the heat keeps seeping in through the ceiling. The next thing most people do is to install air conditioning. This is a knee-jerk reaction, which will barely solve your problem. The unventilated roof will keep transferring heat while you keep using air conditioning for longer. In the long run, your utility bills will surprise you.
Over the years, there have been improvements in the methods that you can use for roof ventilation. Most people are used to the roof whirlybird which has been around since 1910. By design, the principles behind the whirlybird haven’t changed. The turbine still depends on the wind to spin and cool your roof. Another factor is air expansion in the roof cavity, which happens as the temperatures rise.
How Does the Whirlybird Work?
There are two types of whirlybirds:
- The wind-driven whirlybird
- The mechanical, active-powered whirlybird
The wind-driven model is the most common, and popular. It depends on the wind to turn the turbines, thereby rotating the vents. The resulting motion creates a vacuum which sucks air from the roof cavity. As effective as this is, a single whirlybird is unfortunately not enough to cool a modern roof. In fact, most homeowners need up to six units for optimal results.
One benefit of the whirlybird is that it can also help you improve the air circulation in your home, while at the same time reducing heat build-up. This design can also withstand rain, though this doesn’t mean it’s impenetrable.
Is It Effective?
In terms of efficiency, each whirlybird is different. Your results will depend on the model and the manufacturer that you purchase from. However, on average your whirlybird should ventilate between 100 and 150 m3/h for 12 km/h winds. Take note that this performance might not be the same always. There are also other factors that will affect the performance, that have nothing to do with the whirlybird. For example, the accessibility of wind, and how warm the air in the roof cavity is (to allow for expansion). Other than that, the throat size of your whirlybird, wear, and tear will have an impact on the effectiveness of this device.
For efficient ventilation, you need around 700 m3/h of air flow just to keep your roof cavity as close to the outdoor ambient temperatures as possible. This means that you will have to buy more than one whirlybird.
Is the Cost Worth It?
Contrary to what most people might think, a normal whirlybird is quite affordable. Visit any of the local hardware stores and you will find them for around $60 AUD. Apart from that, you can install the whirlybird on your own. While affordability is something you might be excited about, this can be a challenge today, because there are many cheap models on the market, which might not be very efficient.
The following are some of the challenges that you might experience when you buy wind-powered whirlybirds for roof ventilation:
- Dependant on Airflow
To turn the turbines, the whirlybird depends on the wind. Therefore, to put it simply, when there’s no wind, the whirlybird won’t be effective. On a windy day, you can enjoy the best ventilation for your roof. However, on those days when there’s no wind, especially the humid summer days, the sun will have as much fun as it pleases, roasting your roof.
If you live in valley areas, strong winds are the order of the day. Therefore, your whirlybird will always perform optimally. If this is not the case, you might need to consider other alternatives. One such option is a mechanical whirlybird. These are very good, though their prices and cost of operation have proven quite inhibitive in the past.
- Makes a Lot of Noise
Cheap is always expensive. The same applies to whirlybirds. If you get the cheap ones, rest assured they will make a lot of noise, and might also not be as efficient as you would expect. While in operation, the parts of the whirlybird rub against each other, making low grinding or squeaking noises. As the strength of the wind increases, so does the noise. Other than that, the whirlybird has movable parts, which means you should constantly lubricate them. Fail to do this and the bearings will loosen. Should they get damaged out of neglect, your whirlybird will become incessantly noisier.
- Flawed Design
We have already mentioned before that most whirlybirds are quite affordable. Compared with more expensive ventilators in the market, they are inefficient in terms of moving air through your roof cavity. A single whirlybird will never be sufficient for your home. You need more in order to reduce the temperature in your home. In fact, a standard average home requires 15-20 whirlybirds. If you manage to install all these whirlybirds, it will be expensive. Other than that, it will also make the installation costly, cumbersome, and will interfere with the overall look of your home.
- May Malfunction
Whirlybirds are built to work in the rain. However, they feature an open design, which may trap foreign objects, dust, and leaves. The more debris is trapped in the whirlybird, the more likely that it will not perform optimally. There are cheaper models in the market that will not last long before the effect of severe weather damages them. You can avoid this with proper cleaning and maintenance. However, imagine doing that for 15-20 whirlybirds, just to make sure your home is cool. Most people cannot do this so it becomes an inconvenience.
Ventilation for Commercial Properties
An average whirlybird requires 8 km/h wind power for optimal results. Industrial models, however, can operate between 2500 and 5000 m3/h, especially where there are very strong winds.
Even though most people are only used to the whirlybirds for homes, there are also commercial ventilation products available which are designed to help cool down the heat that’s produced in such properties. Other than that, commercial ventilation whirlybirds are designed with exhaust fans that will help propel fumes away from your industrial premise.
Commercial solar ventilators are available in two sizes:
- SW-RAF7000, capable of moving 7,000 m³/h
- SW-RAF10000, capable of moving a whopping 10,000 m³/h!
Dealing with Whirlybird Leaks
A whirlybird is simply an exhaust vent. These vents are built with fins. The fins open as they turn in the wind. This creates a spinning action that draws humid air in your attic outside. Usually, you will not need maintenance for your whirlybird. However, this is not to say that you might not encounter problems from time to time. One of the challenges that you might experience is a leaking whirlybird. While replacing the vent might be a solution, it’s not always the case.
- Obstructions and Rust
The way the whirlybird is designed, even the slightest breeze can turn the turbines. When the vent is spinning, the air that’s blown from it should be sufficient to blow rain from the openings of the whirlybird between the whirlybird fins.
In case you have a rusty vent, it might not be able to turn as it’s supposed to, and will be sticky. As a result, rainwater will leak into the whirlybird. You should inspect the whirlybird because there might be something inside or close to it that might be making it impossible to turn as it’s supposed to. Remove any obstructions close or inside the whirlybird, and replace the rusty vents.
- Loose Connections
When the wind is too strong, the vents might loosen from the standpipe. This is one of the reasons why water can seep into the whirlybird. You will notice that some turbine vents have a friction fitted on top. In case the flange connecting the roof sheath and the pipe is not anchored properly, this will also create an opening for water to seep into the whirlybird.
These are some of the things you need to inspect. Ensure the spinning section has been anchored securely with metal screws. In case the flashing is loose, use roofing nails of rust-resistant screws to fasten it in place. Use roofing cement or silicone caulk to seal around the fastener heads that are exposed.
- Fasteners and Unsealed Joints
Upon installation, several parts of the turbine vents are sealed to prevent water from seeping inside. The parts that are sealed with silicone caulk and roofing cement include the nail heads, the base of the vent, the vertical seams and the bed that connects the upper and lower parts of the whirlybird. The seals will, however, suffer wear and tear over time, and you will need to reapply them to protect the whirlybird.
- Improper Flashing
As you inspect your turbine vents, you might realize that it’s in proper condition, all the fins are in place and it’s running just fine. However, it might still be leaking at the base of the vent. Most of the vents are built with a unique base flashing. The flashing is made from sheet metal. The sheet metal slips above the vent and overlaps the shingles.
In case the flashing is damaged or is bent, the force of the wind can make rain penetrate the whirlybird from underneath. You should, therefore, reattach the parts of the flashing that might be raised, seal the fasteners and edges with roofing cement and caulk. If the flashing is corroded, it might have holes that are holding water. If this is the case, you will have to replace the vent altogether.
Most of the mounted whirlybird ventilators are very easy to install on your own. You should find instructions included when you buy them, which are very simple and easy to follow.
Here are some of the steps that you should follow:
- First, determine the part of the house where the vents will be installed. This should be the side furthest from the entrance.
- Estimate the number of ventilators that will be enough for your roof. The ideal setting should be one vent for every 50 m2 of your ceiling. This might also depend on the type of whirlybird that you buy.
- Make sure you don’t cut through rafters when installing the ventilators. This is because, during installation, most of the roofers often drill nails from the side to indicate the centre line.
- Clearly indicate the parts of the roof that you will saw through.
- In case your house has a metal roof, you must get the right saw blade to use with your reciprocating saw. If yours is a tiled roof, you must first remove the tiles that are in the part you want to cut through.
- Always cut according to the specifications for your reciprocating saw.
- In the course of installation, make sure you use caulk so that rain doesn’t affect the installation.
While installing the ventilation, you have to exercise caution so that you don’t interfere with the roof and create leaks. This is one process that most people fail at.
These are basic steps and they should guide you. However, since ventilation products might be different, the procedure might also differ from one product to another. Where possible, hire an expert to handle the installation on your behalf.
Choosing a Roof Mounted Ventilator
Long before whirlybirds were used in homes, they were common in commercial buildings and industrial settings. Therefore, the style didn’t matter much. However, at the moment there are different types of vents. When you are searching for the best, make sure you get the ones that are rust and corrosion resistant. Make sure you check the quality of the ventilator before you pay for it. Some of the best products come with a warranty of more than 15 years, and they might be more expensive than most of the average ventilators.
Calculating the Amount of Ventilation You Need
The tips below apply for homes that have ventilated antics. There are some homes where the roofing is designed with ventilation space in the roof instead of the attic, especially in flat roof houses. In such instances, you will have to take additional measures to calculate the ventilation.
For ideal ventilation between the attic and the roof, you must establish a good balance. The space set aside for air intake must be the same as the space set aside for exhaust, and this will depend on the slope of the roof, and the size of your attic.
To determine the requirements for ventilation, you must first take measurements for the length and width of the attic floor. Compare this with the net free area (NFA). The NFA is used to rate the vents, which is simply the space set aside for free circulation of air. This makes it easier for you to determine the number of vents you need for the attic.
In case your attic floor is designed with a vapor barrier you will need a square foot of NFA for every 300 square feet of the attic floor. In case you don’t have a vapor barrier, increase this to a square foot of NFA for each foot of the attic floor.
These guidelines are basic, and in most cases, they will cut across the board. However, it’s always wise to consult your local building code.
In case your roof has a steeper slope than most homes, your NFA calculations won’t be the same. The average slope should be 6:12. If yours is bigger than this, you will have to make room for more ventilation. If your slope is in the range of 7-10:12, allow for 20% more space. If your slope is 11:12 or higher, allow for 30%.
Once this is done, you can then choose the type of vents that will suit your home. Remember that it’s safer to have more intake ventilation than a deficiency. Most people get their calculations wrong and they underquote the amount of intake necessary. Therefore, don’t worry yourself about having too much ventilation.
When ventilating the attic, one of the best things you can do is to make use of the warm, moist air and its ability to rise, particularly when cold air under it keeps pushing it up. Owing to normal activities in the home like showering, cooking or human physiology, there’s never a shortage of warm moist air in the home.
You should, therefore, find a way to take advantage of this effect. Your roofer will install intake vents as close to the eaves as possible, and install exhaust vents on the higher side closer to the peak. This helps to push out hot air more efficiently.
Don’t Block the Vents
You should never block the vents. You wouldn’t want to stuff insulation in the vents either. During the winter, ventilating the attic spaces is necessary as compared to the same during the summer. Water vapor from your home will rise into the attic each day.
The Problem with Condensation
If the vapor is not removed from the house as fast as possible, there’s a risk that it will condense on the frame of the roof, or beneath the roof sheath. When this gets intense, water might start dripping from under the roof, and as the temperature falls, it might frost within the attic. These are some of the prime conditions for mold growth or wood rot.
Thousands of CFM per Hour
Turbines can help you propel as much humid air out of the house as possible, depending on the size of the vents, and the speed of wind outside. A turbine vent with a diameter of 12 inches and a steady speed of 5 mph can get rid of more than 340 cubic feet of air per minute (CFM) from the attic.
A turbine bent of 14 inches and a steady speed of 15 mph can get rid of more than 1300 CFM of air. In case the winds are still, the vents will still help with proper inflow and outflow of air through the attic, though not as much as when the winds are strong.
Don’t Steal Heat
There’s always the myth that during the cold months, vents will remove warm air from the attic. In case it’s cold outside while the air in the attic is warmer, you might experience inefficient insulation especially when you’re in the attic on a sunny day.
The best thing to do is to make sure you monitor the attic temperature soon after the sun has gone down at night. With proper insulation, the air temperature in the attic should almost be the same as the temperature outside the house.
There’s also the possibility that turbine vents can draw conditioned air from within your house. According to modern building guides, you should have soffit ventilation vents which will help with air intake.
When the vents are drawing air from the attic, the same amount of air should be flowing into the attic where the roof crosses over the exterior walls of your home. This applies across all types of vents, whether you have an electrically powered fan, ridge vent or turbine vent.
In case the soffit air getting in is not sufficient, you might have a partial vacuum in the attic. This pressure will force the vacuum to draw air from within your home, and you wouldn’t want that to happen.
Aluminum and Rust
Should you decide to add more vents to the roof, consider getting aluminum vents. This is because aluminum doesn’t rust. Other than that, make sure you consider the roof pitch that will be ideal for the turbines you buy. Your turbines should be adjustable in such a way that the spinning section is level even if you have a slanted roof. Remember that all turbines will not always fit your roof pitch. Look at the box label carefully to identify the maximum roof pitch.
Always make sure that all the ball bearings have been sealed and lubricated. You wouldn’t want to have a squeaky turbine making noise, especially on a windy night.