The size of an outdoor fan is based on the size of the fan blades. The blades are critical to the amount of cooling you can expect from your fan. Not only their size but also their number, shape, speed of rotation, even their angle can affect the cooling ability of an outdoor fan. We discuss all of that here, plus the materials they're made of. A smart choice of fan blades can maximize the fan's air flow and cooling ability.
It's good to know if the fan you want to buy will do a good job of cooling an area, or if it will just look good. Understanding a little about the fan blades can help you know that before you buy.
Also, more and more ceiling fan retailers are making it possible for you design your own fan by choosing the fan's blades. You can avoid making a mistake if you just know a little about them, first.
The size of an outdoor fan is measured straight across from blade tip to blade tip. The longer and the wider the fan blades the more air they will move. The size of the area you need to cool will help determine the size of fan to use.
The following outdoor ceiling fan size chart shows some typical outdoor fan sizes and their recommended areas for cooling. Fan size is based on the measurement of the outdoor ceiling fan blades.
This chart is just to give you a general idea -- the numbers are extremely flexible depending on the configurations of any one fan (its CFM, efficiency and wattage) and of any one area. Large areas may require more than one fan. Rectangular, odd-shaped areas, or partially divided areas are best cooled by multiple smaller fans.
|FAN SIZE||AREA||DIMENSIONS||TYPE OF AREA|
small porch, shed, baseball dugout
up to 100
up to 9.3
gazebo, greenhouse, festival booth
up to 144
up to 13.4
medium patio, carport
up to 225
up to 20.9
up to 400
up to 37.2
up to 485
up to 45
up to 600
up to 55.7
event tent, livestock shelter
This chart doesn't apply to wall-mount or standing fans. Most standing fans blades are simply not that large. Plus standing fans of comparable sizes generally move more air than ceiling fans.
To size wall mount fans and floor or standing fans, use the standards of CFM, efficiency and wattage, and follow this rule:
To estimate how much airflow to look for in a fan
multiply the area in square feet or square meters by 3 to 4 to estimate CFM or CMM
The fan's blades can maximize the fan's air flow.
Its often better to use several smaller outdoor fans than one large fan. More, smaller fans can ensure air movement in more areas than just one fan. You'll also be able to use lower fans speeds to get good air flow — softer breezes can be less of a nuisance than stronger breezes. Smaller fans also allow you to concentrate the air flow exactly where you need it. Why fan a whole patio if you only use a corner of it?
Keep at least 24" / 60 cm between the blades of each fan. This ensures the air flow of one fan doesn't cancel out the air flow of another.
Consider using a combination of outdoor fan styles. A small ceiling fan can be used to cool the middle or one side of a patio and a standing fan or table fan can reach the corners.
An open area will allow that moving air to cover as large an area as possible, but will also allow it to dissipate. For example, a canopy or gazebo that's open on all sizes will likely need a larger fan than the same sized area closed on two or more sides. A good general rule to determine how many outdoor fans to use in an open area is that you want to create some air movement where most people will be most of the time.
Since there are no walls or ceilings in open areas, you will need to use a free standing fan such as a pedestal or standing fan, a floor fan, or even a table fan sitting on a wall or ledge.
Especially with floor fans, the air flow originates low to the ground, meaning people moving around in front of it can more easily block the air flow than if it originated from a higher level. You can lower the chances of that is you use an oscillating fan, or several fans set up around the area to "bathe" it with moving air.
Three is generally the most efficient number of fan blades for outdoor cooling. Four to six blades are usually used because the extra 1 to 3 blades makes for a quieter fan. More blades than six is almost always less efficient, but it can be more decorative. Fewer than three blades doesn't take advantage of a motor's power and moves less air. Choose a three-blade outdoor fan when noise level is not as important but cost and efficiency are crucial.
Any more than six fan blades can put more strain on the motor than resulting air movement would justify. The exceptions are specialty outdoor ceiling fans that may use up to ten blades and extend 24 feet across. These use a combination of specialized outdoor ceiling fan blades and motors.
The wider the blade, the more air it will move … up to a point. The fan blades on some very decorative fans can be so wide they would nearly overlap each other. This may not allow enough air in-between the blades for good air movement. If beauty is more important than maximum air flow, these can be a fine option.
Some fans have just the tips of their blades tilted. This doesn't "even out" the air flow the way tilting the entire blade does, but it can affect a wider area of air flow than fans with straight blades. In short, it enlarges the area a fan can affect. This is often seen in standing fans.
Still other fan blades have specialized shapes. Some are shaped like airplane wings with more surface area on the top than on the bottom. Some curve forward. You may need to contact the manufacturer to learn how these special shapes affect the air flow.
Faster blade rotation is basic to greater airflow, which means greater cooling. Blade rotation is sometimes called "fan speed" and is measured in RPM (revolutions Per Minute). It is simply the number of times any one blade makes a full rotation in one minute. An outdoor fan with two speeds will have a lower RPM with less air flow on LOW and a higher RPM with greater air flow on HIGH. Look at the CFM / CMM rating for each speed.
The angle at which the fan's blades are angled up from the flat plane of their rotation is referred to as the "blade pitch". The greater the pitch, the greater the airflow. But as pitch increases so does the drag. So as the pitch increases, so must the power of the motor. Blade pitch usually varies between 9 and 15 degrees. Very strong motors can drive blades with a pitch in the 20s which makes for exceptional air flow.
Some outdoor fans modify not only the pitch of the blades but also their tilt. Tilting the fan blades back (or up, in the case of ceiling fans) distributes the blowing air more evenly around an area. So there's less air flow directly in front of the fan, but more in the outer reaches of the fan's air flow. The air flow is "evened-out."
Fan blades should be made of sturdy, warp-resistant materials. An outdoor fan, being exposed to much harsher elements than an indoor fan, needs to have blades that resist corrosion and warping. The most common materials are aluminum and various kinds of plastics, such as ABS. Heavy duty fans may also incorporate fiberglass into their plastic / polypropylene blades. Materials like rattan and most woods won't hold up to long periods of outdoor use. But aluminum and plastics can be treated to look very much like them and still be durable enough for outdoor use.