[Greenbuilding] Data on energy conservation advantages of ceiling fans

[Michael O'Brien]

Hi, Bob--

Good question! 

A ceiling fan does not change the air temperature in a space--the cooling effect results from skin moisture being evaporated more quickly by air flow across the skin, driven by the fan. It is a real comfort effect but hard to quantify the perceptual aspect. What is some extra comfort worth in your work environment? Might be worth much more than any energy savings, but harder to quantify.

Figuring out the electric load from fans is straightforward, it's just wattage times run time to get kilowatt-hours, and you know your electric rate.

You didn't say where potential savings might come from, so I guess you mean that the current air conditioning set temperature might be raised a bit, with the fan(s) providing some offset? If your AC is not metered separately from other loads in your space, its electric energy use could not be readily measured. So could be a challenge to compare fan energy with reduced AC energy?

AC is usually designed to dehumidify spaces as well as cool the air temperature. So, the perceived effect of fans will be greater in a dehumidified space, because the drier air will evaporate skin moisture more quickly.

There are basically four variables that determine comfort--air temperature, relative humidity, air speed and radiant surface temperatures. It's helpful to evaluate your particular space in terms of the effects of these variables, and which could be most practical and cost-effective to modify. That's why the energy audit that Matt suggests can be really helpful. You might, for example, be surprised at which variables dominate in an older building--often it's the radiant surface temperatures, which point to insulation and/or glazing upgrades.

Very best wishes,

Mike

Mike O'Brien Photography
mikeoregon.zenfolio.com




On Nov 20, 2014, at 10:17 PM, Bob Waldrop <bwaldrop1952 at att.net> wrote:

There's some talk at my work about signing up for the utility's flex hours rate plan, where we pay more between 1 PM and 7 PM Monday through Friday.  I'm thinking . . . if we put ceiling fans in the offices, we could move the thermostat up a bit.  My boss is a data guy, math major in college, and he will want to see some figures. Is there anything convenient out there I could download or give him a link to about how ceiling fans can save energy dollars?

Bob Waldrop, Okie City

-- 
http://www.ipermie.net How to permaculture your urban lifestyle and adapt to the realities of peak oil, economic irrationality, political criminality, and peak oil.


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