Sleep in comfort on hot summer nights – and cold winter ones too

Ceiling mount fans are a much better option for staying cool in summer, than rushing off to the big box store and buying a cheap room air conditioner.

Cheap room air conditioners save money up front, but you wind up paying way too much in the long run, because the “big box” stores focus on up-front price, not total operating cost, and more importantly, because even the most efficient ENERGY STAR room air conditioner is going to use way more electricity than most ceiling mount fans for the same amount of cooling.

The difference, of course, is that ceiling mount fans don’t actually cool your room; they just blow the air around, so that you feel much cooler. Any sweat on your skin – or moisture on the bedsheets, originally from your sweat – is blown away, and this evaporation cools you down. And the amount of electricity required to run most ceiling mount fans is a small fraction of what an air conditioner requires.

Another benefit of ceiling mount fans is that you can use them in the winter as well as the summer – to keep hot air circulating throughout your living space, instead of always clumping around the ceilings (remember, heat rises). Try doing that with an air conditioner!

In this article I’ll cover the following points about ceiling mount fans:

Summer advantages – how they save energy

The ancient Egyptians figured out air conditioning millennia before the first Freon-based room air conditioner was invented. The fan bearer who stood to the right of the Pharoah, holding a full-height feathered fan, played an important and honored role, and kept the air moving around the king to keep him cool.

In hot weather, humans sweat. Much of the cooling action from ceiling mount fans and from Egyptian feather fans alike comes from the evaporation of moisture on human skin. As you might have learned in high school physics, evaporation is a cooling process, and when liquids evaporate they take some of the heat from the air or the solid they were on away with them.

This is important to remember: if there’s no human skin around to evaporate moisture from, ceiling mount fans don’t do much good. A ceiling fan will not actually cool a room down; it will just make the people in it feel cooler, assuming they aren’t already so dehydrated that they have no moisture on their skin!

If you actually want to cool a room down (as in lower the temperature), a better choice may be a window fan unit, since you can use the fan to draw cooler air inside or blow excessively hot air out. This works great when it’s cooler outside than in, as is often the case from dusk until dawn.

Ceiling mount fans can cause some increased ventilation with the outdoors if you have wide open windows (i.e. no screens), but even the partial barrier of a screen will reduce the air cooling effect of the fan to near zero. If there isn’t water to evaporate, turn the fan off. This is so important I’ll give it a paragraph of its own:

Don’t leave ceiling fans on in hot weather in empty rooms!

Leaving an air conditioner running in a room you’ll come back to later doesn’t make that much sense either – but at least it cools the room down so you’ll be able to enjoy the cool air when you get back. Keeping the air moving inside a room, without reducing its temperature, really doesn’t accomplish anything!

Winter benefits – keeping the heat circulating

As I mentioned earlier, hot air rises. In winter, this means that the temperature difference between the floor and ceiling of a room can be substantial, especially where the heat source is projected upwards from a floor forced air register or originates higher up (for instance, a kitchen stove used for cooking, or a fireplace that vents heated air out the top).

If you have cathedral ceilings, the distance from floor to ceiling can be as much as twenty feet (that’s the peak height of the ceiling in my parents’ country home). Of course, no one ever hangs out up at the peak – unless Uncle Albert happens to be visiting and someone cracks a joke – so there’s no point in letting the heat all rise to the ceiling and stick there.

That’s where ceiling mount fans come in handy during the winter: use the fan to draw air from below up to the ceiling, which in turn pushes the hot air at the ceiling down the sides of the room and back to the floor, where it can start rising once again.

When you use ceiling mount fans in winter, you don’t want the fan to blow straight down on you, and you want it to run slowly – just keep the air moving, rather than create a hurricane. But that little bit of upward draft of cooler air, and downward push of the hot upper air, can go a long way to keeping the heat where you want it, around human bodies, instead of up near the ceiling, where (especially if the ceiling is against a roof or attic) the heat will eventually escape upwards.

Speaking of heat moving upwards, a ceiling fan at the top of a stairwell is also not a bad idea. You can use it to send hot air back down from the bedroom floor to the living room floor of a two storey house. Or, if you heat with a living room fireplace insert as I sometimes do, a ceiling fan can be used to increase air circulation between the two floors, and draw the hot downstairs air up more quickly. (We can sometimes get the temperature to 85F downstairs and be freezing upstairs, because the fireplace causes the furnace thermostat in the front hall to switch off!)

Which direction should ceiling mount fans turn?

You can probably figure this out for yourself if you’ve read the sections above on how ceiling mount fans cool in summer and add warmth in winter, but let’s cut to the chase.

Summer fan direction: In summer, to keep cool, you want the fan to be blowing air straight down onto you. Rather than worry about whether that means clockwise or counterclockwise, just turn on the fan, and try both directions. The one that blows straight down on you the most is the right direction. (If you really do care, for most fans the direction you want is counterclockwise.)

Winter fan direction: In winter, you are trying to move air up the center of the room towards the fan, which then blows it out above it and down the outside edges of the room. So again, turn the fan on and try running it in both directions; the one that blows straight down on you is the wrong direction, instead choose the direction where the effect is much less airflow from above and more from the sides. (And in this case the direction you want is clockwise.)

And remember, for winter fan direction, choose a low speed. You want to keep the air gently moving to keep heat coming back down into the inhabited parts of the living space. You don’t want to blow the moisture off people’s skin and cool them down!

How much electricity do ceiling mount fans use?

Here’s one of the main reasons ceiling mount fans are so energy efficient – even the largest home ceiling mount fans use only about as much energy as an incandescent 100 watt light bulb.

Take a typical, ENERGY STAR rated small room air conditioner at 5200 BTU with an EER rating of 11. The Energy Efficiency Ratio is a ratio between BTU/hour of cooling power, and watt-hours of input, so for such a room air conditioner, the power consumption would be about 470 watts. A high-powered ceiling fan is thus five times more efficient than the lowest capacity room air conditioner. And that’s when it’s running at full speed. Most people need about 15 minutes of full-speed airflow from their ceiling fan when they settle into a bedroom for the night, after which they can switch the fan to half speed and use just one tenth or less what the air conditioner uses.

Here’s a table showing typical power consumption of energy efficient ceiling mount fans by blade size, with ratio to that ENERGY STAR rated EER 11, 5200 BTU air conditioner (note that blade sizes are the diameter of the circle formed by the turning blades – not the length of an individual blade).

Fan blade size Watts consumption, full speed Times more efficient than small room AC
36 55 8.5
48 75 6.3
52 90 5.2
56 100 4.7

At half-speed, your ceiling mount fan will use about half as much as the above. That means for a typical 48″ fan, running at half speed (around 40 watts), and assuming you pay about ten cents per kilowatt hour of electricity, you can run the fan for ten hours and your total electricity cost will be four cents!

Choosing a ceiling mount fan – size

You can buy ceiling mount fans in a variety of sizes, from mini-ceiling fans with a blade diameter around 2.5 feet, all the way up to 4.5 feet (54 inches) or more.

The size of ceiling mount fan you choose will depend on your room size, and, for very large rooms, on the number of fans you decide to install.

Under 36″: Fans with a blade diameter under 3 feet are intended for compact rooms – less than 80 square feet or 7 square meters, for instance an 8 x 10 or 9 x 9 bedroom.

36 to 42″: Fans with a blade diameter of 3 to 3.5 feet are suitable for rooms up to 150 square feet or 14 square meters – a 10 x 15 or 12 x 12 foot room for example.

42″ to 48″: Good for rooms of 150-225 square feet or 14-21 square meters.

50″ to 56″: Rooms up to 400 square feet or 37 square meters; for larger rooms, use two or more ceiling fans.

Choosing a ceiling mount fan – mounting system

Ceiling mount fans are intended to be installed on ceilings that are at least 8 feet high. Installing a ceiling fan on a lower ceiling, or above a raised area (for instance, a bunk bed) is dangerous because of the risk of injury to people from the rotating blades. Even a ceiling fan beside a bunk bed can pose a hazard, especially if it is turning in the dark and a child climbs the bunk bed ladder and reaches out towards it. So make sure you have enough room between the blades and where people can reach upward.

Ceiling fans should also be positioned so that there is at least a foot and a half of space between the tips of the blades and any wall.

Standard ceiling mount fans come with a spacer rod that is 3 to 5 inches long. This spacer connects the ceiling bracket to the fan itself. Most spacer rods are 1/2″ or 3/4″. You can buy longer spacer rods of anywhere from 6 inches to ten feet – a very long spacer is suitable for a space with a very high ceiling, where the main desired effect is cooling (for heating, the fan does need to be close to the ceiling, otherwise in winter you aren’t going to push the hot air at the top of the room down, only the warm air halfway up).

For very tight vertical spaces, where you can’t even afford a 3″ spacer rod, you can buy a flush mount fan specifically designed for a low profile. These fans are also called “Hugger” fans. Note that they are not as energy efficient or as effective as standard mount fans, because the proximity of the blades to the ceiling means they require more energy to move the same amount of air around (or use the same amount of energy to move less air around).

Where you are adding on a light unit to an existing fan, the lamp may protrude too far down with a standard ceiling fan, which is another good reason to look for a hugger or low profile fan.

Don’t forget about quality – and ENERGY STAR efficiency

The fan motor is one of the key components of all ceiling mount fans, and buying a unit with a high quality motor will ensure you higher efficiency, longer life, and quieter operation. A higher-power motor will typically be more efficient than a smaller one for the same fan blade size. Also, look for a motor with a thick metal casing, which will help reduce wobbling and vibration. Features to watch out for are a lifetime warranty (or a lifetime warranty on the motor at least) and an ENERGY STAR rating.

Buying an ENERGY STAR qualified ceiling mount fan can save you more than the price of many such fans over a ten year period – $15 a year or more. ENERGY STAR rated ceiling mount fans are required to meet a number of efficiency criteria, including:

  • A minimum of three fan speeds (low, medium and high)
  • Improved airflow in cubic feet per minute (CFM) per watt of energy input. More below.
  • A minimum 30 year warranty on the motor
  • Readily accessible controls to change the fan speed and reverse its direction

Fan speed and efficiency requirements are:

Fan Speed Minimum Airflow Efficiency Requirement
Low 1,250 CFM 155 CFM/watt
Medium 3,000 CFM 100 CFM/watt
High 5,000 CFM 75 CFM/watt

Maximizing the efficiency of your fans

Moving the air around in one room will keep people cool in that room, but won’t do much for the people in other rooms. So place ceiling fans in any room where you expect to need cooling capacity in hot weather while the room is occupied.

Remember to place the fan blades at least 10-12 inches from the ceiling. This is especially important for wintertime heat recirculation, as blades that are too close to the ceiling will not have much effect on recirculating hot air back downward. The same applies to fans that are suspended more than 12 inches from the ceiling on very tall ceilings: the further down the fan is relative to the ceiling, the less effective it will be at recirculating hot air at the top of a room down the outside walls of the room towardsthe living areas.

Balancing your fan blades

It’s important for your fan blades to be properly balanced. A wobbly fan can become an annoyingly noisy fan, and can pose serious safety risks.

I learned this first hand while living in a rented house in Costa Rica during a year’s sabbatical in 2008-2009: two of the four ceiling fans in our living area were wobbly, and one of them came crashing down, while spinning at top speed, within a few feet of where my six-year-old son was sitting at the table drawing pictures.

This ceiling mount fan was attached to a ceiling joist with a single drop tube that had been split at the top end to form two brackets. The constant rocking caused by improperly balanced blades had pulled one of the two screws loose that held the fan in place, and the continued wobbling (probably exacerbated by the fact that the fan now hung at a slight angle off the horizontal) fatigued the metal where it was screwed in on the other side, and eventually snapped that tab until the fan crashed to the floor.

When the property manager investigated, he discovered that one of the other fans (the other one that wobbled) was also hanging by just one half of the bracket and would have fallen within a few weeks.

Most fan blades are calibrated and balanced prior to shipment, but if the fan does seem wobbly after you install it, you may be able to solve the problem easily. Try realigning all parts and tightening all connections. Hold a yardstick vertically to the ceiling from the tip of each blade, to ensure all blades are at the same distance from the ceiling; you may be able to get a blade readjusted to the right distance by gently bending a misaligned blade holder back into place. (If the blade holder is badly misaligned, you may need to return the product to the point of purchase for replacement.)

Assuming the blades are properly aligned and all connections have been checked, you can often obtain a balancing kit – clips and weights for the blades – which can be used to find the underweight or overweight blade and balance the fan as required. These kits usually come with the fan unit or are shipped free of charge, on request, from the manufacturer.

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