Friday, August 7, 2009

Did Someone Really Claim Ceiling Fans Lower Ambient Temperature 5 Degrees?


I did a double take. The article didn't claim ceiling fans lower temperatures did it?

You really can’t beat a fan for cooling efficiency; a $100 ceiling fan costs less than $10 a month to operate 12 hours a day and can cool a room by 5 to 7 degrees!

Source

It said it. What bunk!

Ceiling fans cool people, not air. If anything, ceiling fans raise the air temperature slightly due to heat generated by the motor.

By increasing air movement, ceiling fans help people feel more comfortable at a higher ambient temperature by increasing the evaporation of perspiration. Air movement facilitiates the anatomical air conditioning system that God gave each of us.

It works like this... People perspire whether aware of it or not, and the evaporation of perspiration pulls heat from the skin as the perspiration changes state from a liquid to a vapor. This change of state requires energy. The energy comes from heat sucked from the surroundings, lowering skin temperature. It's why we pretend Phoenix is almost bearable without air conditioning because it's a dry heat.

But ceiling fans are only effective when humans are in the room to benefit. Leave the fan on after you leave the room and you're simply paying to turn the blades with no benefit. Fail to change the thermostat setting and there's not even a benefit when you're in the room.

Even Consumer Reports acknowledges this simple fact of physics...

Unlike air conditioners, ceiling fans won't lower a room's temperature or remove humidity. Save energy and money by using ceiling fans and turning off the air conditioning or by turning up the A/C's temperature a few degrees and letting the fan do the rest. But remember that ceiling and portable fans cool you, not the room, so don't run them when you aren't there.

Well, guess what? Most people don't turn the fans off when leaving a room. Most people don't even change the thermostat setting, according to Arnie Katz at Advanced Energy.

"A study in Florida," noted Katz, "found that there was no difference in thermostat settings for people using fans and not using fans. If you don't turn up the thermostat, then the AC will run just as much, and you won't save a dime."

Katz continued, "In order to be economical, you have to think of the fans like you think of lights. Or, rather, like my grandmother thought of lights. You go into a room, you turn on the light (fan). You leave the room, you turn it off. Blowing air onto your living room carpet or onto your bed, when no people are there, will cool nothing except the dust mites. I go into houses all the time and find three or four or seven ceiling fans running. And folks actually believe they are saving energy."

Okay, so it's one rogue guy, posting made up numbers on the Internet. That's nothing to get all worked up about.

Well, I'm not sure it's one rogue guy. The link at the end is to a ceiling fan manufacturer. If they're responsible for the claim, I wonder what else they're lying about.

The other problem is stuff like this has a tendency to grow legs and run around the Internet, especially if its clothed in green. While I advocate improving energy efficiency when the consumer wants it and the ROI justifies it, much of the green movement loses touch with economics, physics, and freedom of choice. Someone makes up some numbers to back up a made-up claim and the next thing you know, Congress is passing mandates.

This goofy claim is already getting repeated in an article obscenely titled How To Live Without Air Conditioning (The mere thought makes me shudder). There are even claims suggesting it's possible to save 33% on energy bills with ceiling fans.

As a nation if we're going to make investments in energy efficiency and energy production, we need to make those investments where the returns are best. That leads to greater national wealth and it's only wealthy countries who can afford to keep the environment clean. If uneconomic and ill-conceived mandates and restrictions that reduce wealth are forced on people in the name of the environment, a backlash against the green movement will arise.

This isn't an anti-ceiling fan screed. Personally, I like ceiling fans. I like the air movement. I think they look cool. I've got them all over our office building and in most rooms at home. Yet, I don't change the thermostat setpoint and at home, no one shuts them off when leaving a room. I don't pretend I'm saving money by running ceiling fans.

This isn't a screed against ceiling fans, it's a screed against phony data and claims.

3 comments:

  1. I found your article searching for fans that reduce temperature. You are right fans don't decrease temp.
    But there is fan that supposedly does, its works like an air cooler but does not use water.
    The air passes through some german technology membrane that reduces the temperature of the air upto 7 degress. The longer you run it it can actually reduce temperature of the room.
    I saw it an exhibition. They held a thermometer in front of the fan.
    It looked like those tower fans.
    Have you see any of those? I wanted to search to net to see if anyone has used those and does it really reduce the temperature

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  2. I found I could turn the A/C up a couple degrees if I turned the fan on before bed. Not sure if I actually saved electricity.

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