Comments on: How Energy Efficient Is Your Ceiling Fan?

By: Bob

Bob — Sat, 21 Jul 2012 02:29:21 +0000

I too fail to see the logic
I too fail to see the logic of spending $500 for a high CFM per watt fan. Most fans are bought for decorative reasons, but I'm glad to see the CFM/Watt ratings. CFM/watt could be a tie breaker for some people.

What I'd REALLY like to see is how distance mounted from ceiling affects CFM/watt. This makes a HUGE difference compared to motor/blade design. Smaller fans take less of a hit than larger fans when mounted too close. Mount a 36" fan 8" from the ceiling (think 'hugger' style) and do the same with a 52" fan. Both will move about the same amount of air (neither will move much) while the 52" consumes more power. Using the longest downrod that keeps the blades at least 7' above the living space (for safety reasons) will maximize CFM.

By: M. Johnson

M. Johnson — Thu, 19 Jul 2012 15:20:26 +0000

I wonder if anyone has seen
I wonder if anyone has seen numbers published, measuring what percentage of household electric use, is consumed by ceiling fans.

Has anyone ever paid the same attention to the efficiency numbers for portable fans? In many peoples eyes ceiling fans are chic and box fans are gauche. But in a place like Houston when poor people have trouble with AC bills, the official stance of the electric company is they should use fans in place of AC. This makes the fanfare for the $500 super efficient ceiling fan seem positively elitist.

By: Andrew

Thu, 19 Jul 2012 08:43:18 +0000

It has been a couple years
It has been a couple years and I think people are more aware but I spent some time working in a big box store and the overwhelming majority of folks purchased fans based on cosmetics and price. I am probably like them, I am pretty particular about ceiling fans in different rooms.

By: Ted

Ted — Wed, 18 Jul 2012 18:46:25 +0000

Allison, yet another awesome
Allison, yet another awesome blog post! That Farmington label seems a great example of fans law.

Now, if there were a way of tying that back to maximizing efficiency of design and operation of hvac...

"Keep it as low as possible at all times"?

By: Allison Bailes

Allison Bailes — Mon, 16 Jul 2012 22:55:58 +0000

M. Johnson
M. Johnson: Yes, the Gossamer Wind fans are sold in the big box stores. The one I mentioned in the article that's rated at 106 cfm/watt is one of them. You may not have found them because they're sold under the name Windward. The one I saw is the Windward IV made by Hampton Bay. Martin Holladay wrote a great article about ceiling fans (I'm adding a link to it in the Related Articles list above.) a couple of years ago, and the comments have more info about the Gossamer series.

Jeffrey: Great points! Yep, fans on porches are great, for both keeping cool and bug-free. I love the term 'gnat knockers.'

By: Jeffrey

Jeffrey — Mon, 16 Jul 2012 22:48:16 +0000

From a consumer perspective,
From a consumer perspective, it's great to see that fan efficiency is getting measured and labeled.
In the HERS world, there's still difficulties in collecting this information by raters though. Said box is hardly ever around when a rater does their inspection(s) and even if it happened to be in the trash container the day the rater shows up, it appears from your retail research that the efficiency listed is often the cfm/watt at the highest fan speed. The HERS standards require the efficiency rating at the medium speed setting. Assuming the rater can find the model #, I guess an internet search seems to be the best way to collect this information.

BTW, don't forget the other amazing benefits of ceiling fans: odor dissipation and insect retardant. (Fans on porches in the deep South are affectionately called "gnat knockers".)

By: M.Johnson

M.Johnson — Mon, 16 Jul 2012 20:43:37 +0000

Do you remember a few years
Do you remember a few years ago when Florida Solar Energy Center reported on a high efficiency ceiling fan? It was called the "Gossamer Wind" if I remember. Rather than the usual blunt blades or mock palm leaf blades, it had blades which tapered along the length. It looked more like an airplane propeller than what we are used to... probably not by coincidence as propellers are engineered to move the most air they can with a given amount of power.

I was told the Gossamer Wind series was available through big box stores such as Lowes, but I never saw them displayed. It may underline the fact you have many electricity uses ranging from 100-4000 watts, and optimizing the one that rates 34 watts just is not high on the priority list.

By: Allison Bailes

Allison Bailes — Mon, 16 Jul 2012 18:43:07 +0000

Chris K.:
Chris K.: Yeah, Big Ass Fans aren't cheap. I look forward to your review.

TC Feick: You could show her some infrared images to scare her straight if that doesn't work.

Charles: Great points. I don't know what the testing requirements are but I'm sure they include proper installation. Of course, as you state, once the fans get installed in someone's home, there's no guarantee they'll perform at the stated efficiencies. As they say for cars, your mileage may vary. Or for financial investments, past performance is no guarantee of future results.

By: Charles

Charles — Mon, 16 Jul 2012 18:00:57 +0000

Thanks Allison. I wonder if
Thanks Allison. I wonder if those labels on CFM also disclose the conditions under which the fans were tested (is there an NFRC for fans?). Ceiling fans can do a couple of different things in a home, and actual results for air movement will largely depend on actual installation, not the store label. By and large a ceiling fan will do two things: increase the flow of air in a given direction, and, largely as a result of the first, de-stratify the air in a room. This de-stratification can be a good or a bad thing (think about it), but by and large if you are FEELING moving air then you will feel cooler, and especially in summer months that can be a good thing. And whether your windows or doors are open in the fan room can really start to complicate things (some ways good, some ways bad - and may actually drive an exception to the rule about turning the fan off when leaving the room in the right pressure conditions). Note that many fan kits come with varying lengths of extender rods. I've seen many installations where the short 8" rod is used and I could almost guarantee that the fan is not achieving optimal performance. A too short air space above the fan can/will impede the performance of the fan.

By: T.C. Feick

T.C. Feick — Mon, 16 Jul 2012 17:59:45 +0000

Allison, Thank you. My
Allison, Thank you. My constant admonishing to my wife about turning off the ceiling fans when there is no one in the room has gone largely ignored and rejected. I now have some street cred to back me up.