A ceiling fan is a nice accessory for an outdoor living space. But what is the right size needed for it? Is a very large fan the best solution? Which is more important; wind speed or airflow rate? These are the common questions that pop into the minds of those looking to buy a ceiling fan for their outdoors. Here’s how big an outdoor fan needs to be;
An outdoor fan should be larger than an indoor fan to cover the same square feet area. A 52-inch size fan is suitable for outdoor areas up to 100 sq. ft, 60 inches for areas up to 225 sq. ft, and 72 and 84 inches for 400 and 625 sq. fts respectively.
Outdoor fan size
It is easy to calculate the size requirements for an indoor fan based on the square foot area of the room. However, in an indoor space, the air moved by the fan recirculates, adding to its chilling effect. But outdoors, since there are mostly no walls, the air circulation spreads out. In addition, the encasement of outdoor areas differs; some areas have walls on three sides, some may have none! Therefore, you will need a bigger fan for outdoor areas.
Given below are the recommended outdoor ceiling fan sizes for different floor area sizes;
|Total Floor Area of Outdoor Space (Square Feet)||Outdoor Fan Size (Blade Span)|
|Up to 100 square feet||52 inch|
|100 to 225 square feet||60 inch|
|225 to 400 square feet||72 inch|
|400 to 625 square feet||84 inch|
|More than 625 square feet||Use multiple fans of any of the above sizes|
As you can see in the above table, the sizes of outdoor fans are larger than the indoor fan size for the corresponding area. For example, an outdoor fan requires only 50 inches of blade span for an indoor area of 225 square feet, whereas an outdoor fan is 60 inches.
PS: What is the blade span of a fan: For those who don’t know, the blade span of a fan is its diameter. It is two times the length measured from the center of the fan to the tip of a blade.
Relationship between indoor and outdoor fan size – Calculation
Unfortunately, a general sizing chart for outdoor fans is not available anywhere, which is why I created it on here. As I said, an outdoor fan should be larger than an indoor fan for the same square feet area of the space. We can establish a relationship between the fan sizes based on blade span and square feet. Here it is;
A fan suitable for an indoor space with length ‘L’ feet and width ‘W’ feet is suitable only for an outdoor space with square feet floor area not exceeding the multiple of (L-5) and (W-5). For example, a fan suitable for an indoor space of 15′ x 15′ is suitable for an outdoor space only if its floor area is less than 10′ x 10′. (Source)
This is what it looks like when some examples are added into a comparison table;
|Blade Span of Fan||Maximum Indoor Floor Area||Maximum Outdoor Floor Area|
|42 inches||144 square feet||49 square feet|
|52 inches||225 square feet||100 square feet|
|60 inches||400 square feet||225 square feet|
|72 inches||625 square feet||400 square feet|
|84 inches||900 square feet||625 square feet|
Height and spacing requirements for outdoor fans
An outdoor ceiling fan works by pushing the air under it downwards. This airflow increases the air circulation in the outdoor space and creates a chilling effect.
But to create this airflow, there should be enough distance between the fan and the walls of the room including the ceiling and the floor.
|The minimum distance between fan and ceiling||8 inches|
|The ideal distance between floor and fan||7 to 8 feet|
|The minimum distance between fan and wall||18 inches|
|The minimum distance between two fans||36 inches|
Minimum distance between fan and ceiling
When a ceiling fan pushes air downwards, that air is replaced by the air from above its blades. So there should be ample room between the ceiling and the fan blades for the air to replenish. However, if they are very close, this flow of air will be obstructed, lowering the overall airflow from the ceiling fan.
How far should a ceiling fan be from the ceiling? The minimum distance between the ceiling and fan blades should be 8 inches. This distance provides sufficient space for air to move above the fan blades and get pushed down.
What is mentioned above is the minimum distance. Any distance above this will not adversely affect the airflow of the fan. So it is totally acceptable to use extended down-rods to hang a fan much lower in outdoor spaces with high ceilings. However, for every 2-inch reduction from the aforementioned minimum distance (8 inches), the airflow from the fan will reduce as much as 25 percentage. That means a fan with a 4000 CFM rating will only move 3000 CFM of air if installed only 6 inches away from the ceiling. As you can see, this reduction in airflow is enormous. This is the reason why flush-mounted fans do not move as much air as standard fans.
Vaulted or angled ceilings
Some outdoor spaces have vaulted or angled ceilings. When you install a ceiling fan on an angled ceiling, its blades are closer to the ceiling than the fan’s center. This proximity depends on the slope of the roof and the height of the fan’s downrod.
Let’s consider how air flows for a ceiling fan installed on an angled ceiling. In most cases, only one side of the fan is close to the ceiling, so the airflow gets obstructed there. However, the other sides of the fan have ample room to let air move. Therefore, an angled ceiling provides enough room for airflow even though one side of the fan is very close to the ceiling.
So how far away should a fan be from a vaulted or an angle ceiling? There is no minimum distance, the only thing to make sure is that the fan blades shouldn’t touch the ceiling when running.
The length of the downrod required for a vaulted or angled ceiling is calculated by dividing the multiple of the fan’s blade span and the rise of the room (the distance between the lowest point of the ceiling to its highest) by the full length of the room across the slope.
For example, if the room is 15′ x 15′ and the ceiling’s rise is 7.5′ (45-degree slope), then for a 60-inch fan, the minimum downrod length should be 7.5 x 5 (blade span in feet)/15 = 2.5 feet.
Whether indoor or outdoor, the fan should not be installed at the top point of a vaulted ceiling. Due to the vaulted shape, the hot air will be trapped at its apex. So fan installed at this point will be pushing down hot air instead of creating a cool breeze.
Distance between floor and the fan
The chilling effect of a ceiling fan is only effective up to a certain distance downward. Simply said, a ceiling fan won’t cool you if you hang it 20 feet above the floor. So how far should a ceiling fan be from the floor? To feel the best effects of its airflow, an outdoor ceiling fan should not be installed too high or dangerously low. Its ideal placement is 7 to 8 feet from the ground.
An 8 feet high room is the right size for a ceiling fan. As there should be 8 inches between the fan and the ceiling, that leaves you with 7 feet and 4 inches of height from the floor. A person sitting under the fan within this distance should feel a wind-chill effect, which is the whole point of using an outdoor fan.
What is wind chill effect
A ceiling fan doesn’t lower the temperature of a room to create a cooling effect. Instead, it removes heat from your body by circulating the cool air in the room against you. This cool air absorbs the heat from your body, which causes you to feel cool. This is called the wind-chill effect. A fan can make you feel cooler by as much as 4 degrees, even though it doesn’t reduce room temperature.
Distance between the fan blades and the walls
The trend now is to use large fans in small areas. Sometmes the fans can look out of place. Other than that, the close proximity of the walls to the fan can obstruct the airflow to its blades, thus effectively lowering the fan’s effectiveness.
How far should a ceiling fan be from the wall? There should be at least 18 inches distance between the wall and the tip of the fan’s blades when they are closest.
As outdoor areas generally lack walls, this is somewhat irrelevant. However, since areas like porches and patios have one or two walls make sure to keep this distance in mind during fan installation.
Space between two fans
Just like there should be enough space between the fan and the walls, there should be some distance between two fans. It is common to install more than one fan in an outdoor area. In such cases, the fans should have sufficient space between them not to obstruct the airflow of the other.
So, how far apart should two ceiling fans be? There should be a minimum distance of 36 inches from the blade of one fan to that of the other when they are the closest. That is twice the distance the fan should be from a wall.
Ideally, an outdoor fan is installed at the very center of the ceiling. However, when there are two similar fans, they should be apart by twice their distance from the closest and equally spaced from the center. But there is no steadfast rule here. But make sure to hang the fan closer to where you sit.
Is a large fan the best option for outdoors
The general recommendation is to buy the biggest and highest airflow fan for an outdoor area. This is because, due to the lack of walls the air doesn’t recirculate through an outdoor living area. This effectively reduces the air movement in the space. A bigger fan will make sure that most of the area is covered by it. In addition, the chilling effect of the fan is felt only when sitting under it. So the bigger the fan and the CFM, the better.
Airflow vs Wind speed
Some people use the term wind speed on fans. The difference is that airflow is the amount of air moved by a fan, whereas wind speed is the speed of breeze created by the fan. A large fan can run really slow and move thousands of cubic feet of air while not creating a feelable airflow. But a smaller fan has to run really fast to create that much airflow. But in the latter case, you will feel a strong wind. That is wind speed.
For an outdoor fan, wind speed matters more than cfm. Since there is no recirculation of air outdoors, the fan needs to generate a breeze to make anyone under it comfortable. This is why getting a large fan with the highest CFM is recommended, as such fans will run fast, creating a cooling effect.