Here we are in the middle of air conditioning season. So why don’t we chop down some myths and misconceptions about ceiling fans?

What got me on to this topic was a video of a fan with blades that hide on top of the fan when the fan is turned off. Sounds clever, but it’s a ridiculous idea.

Anyway, here are seven things about ceiling fans that a lot of people seem not to know.

1. Ceiling fans heat the room

Yes, a ceiling fan is a cooling device. (See point number 2 below.) But its effect on the room it’s in is to add heat. Why? Because electric motors are devices that turn electrical energy into mechanical energy, most of which ends up as heat. The infrared photo reproduced as Image #2 (below) shows a ceiling fan motor that’s hotter than the room it’s in. From thesecond law of thermodynamics, we know where that heat is going — into the cooler room.

The net result of running a ceiling fan is that you’re adding heat to the room.

2. Ceiling fans cool people

Ceiling fans are useful for cooling only when they move air over skin. They cool our bodies two ways: by aiding evaporative cooling and by aiding convective cooling. If the air movement created by a ceiling fan isn’t hitting anyone’s skin, it’s just making the space warmer with no cooling benefit.

3. A fan’s efficacy tells you how well it moves air

这些天在美国出售的每个新吊扇都是标记有功效。(Efficacy is an efficiency rating wherethe output and input quantities have different units。一个好的风扇会为您每瓦超过100 cfm提供。贫穷的人可能低至每瓦30 cfm。

下次您寻找吊扇时，请检查标签。

4. Bigger is better with ceiling fans

While you’re checking those labels, you may notice a correlation. Thefans with the longest blades have the highest efficaciesand those with the shortest blades have the lowest. That’s why the company Big Ass Fans makes big ass fans.

And it’s why you’ll want to avoid the little short-blade fans, no matter how cute, if you’re interested in air flow. If you just want cute, though, go ahead.

5. Lower speeds are more efficient

查看风扇功效标签时，您会注意到的另一件事是，当您在媒体上运行风扇比在高位上和低点相比，在介质上运行风扇时，您将获得更多的CFM。这里唯一合乎逻辑的结论是让您可以适合房间的最大风扇，留下适当的间隙，并以最低的速度运行，使您保持舒适。

这就是为什么大屁股粉丝公司最初被称为HVLS粉丝公司的原因。HVLS代表大量，低速。

6.如果您有空调，吊扇可能不会为您节省任何钱

Martin Holladay covered this inhis ceiling fan article from 2010, but it’s worth reviewing. If you don’t have air conditioning at all, having some kind of fans can preserve your sanity. You get to keep cool for a relatively low cost.

但是，一旦拥有空调的房屋，动态就会发生变化。那个在皮肤上移动的空气仍然感觉不错，空调产生的低温，低湿气也是如此。假设是，如果人们感觉到吊扇的微风，但数据不支持它，他们将提高交流恒温器设置。

In 1996, the Florida Solar Energy Center (FSEC) did a study of homes with ceiling fans. They found that even though the fans ran more than half the day in the test homes, they saw no difference in thermostat setpoints in homes with ceiling fans compared to homes without.

简而言之，要为吊扇节省您的能源费用，您必须将恒温器设置为更高的温度。我在我家中这样做，但FSEC发现大多数人没有。

7.吊扇会使您斩首

我什至不知道这个神话直到我看到下面的神话巴斯特视频。显然，有些人担心会被吊扇砍掉。正如您在下面的视频中所看到的那样，它肯定会发生……但是，只有当您用更强大的电机（例如割草机电机）替换电机并用剃须刀变种的刀片更换刀片。

So relax! You won’t get your head chopped off by a (normal) ceiling fan. But you can certainly use more energy and make your home warmer by using one.

Oh, and that fan with the nesting blades is a ridiculous idea because it has two problems: The blades have to be short to be able to nest together on top of the motor, and the blades are designed for nesting, not moving air. If you don’t like the looks of a ceiling fan, that’s fine. But why even have something like this at all if it’s not going to move much air?

Allison Bailesof Decatur, Georgia, is a speaker, writer, building science consultant, and the author of theEnergy Vanguard Blog。You can follow him on Twitter at@EnergyVanguard。