[Greenbuilding] But What if? / Re: Ceiling Fans at Night

[Corwyn]

On 1/6/2011 12:06 PM, Frank Cetera wrote:
> /
> ""We do have a programmable thermostat and have it set for 66 during the
> day; at 5pm it goes to 60 and at 7pm it goes to 55 (on the weekends it
> may even be lower). Brent's (the building manager) theory is that even
> at 55, keeping the fans on all night (and weekends) will keep the space
> slightly warmer and therefore the furnace would need to kick in slightly
> less often. Our theory is that the energy expended keeping the fans
> going when the thermostat is set for the lower temperature is more than
> that saved by the furnace kicking in a little less often. Two more
> details - the heat registers are at the ceiling level (go figure); the
> thermostat is on a post about 5 feet up, near an edge of the room. Any
> idea who is correct? Do the fans stay on all the time or can we turn
> them off at night and on the weekends?"/

How many degrees of stratification are you seeing on a night when the 
inside temperature as at 55?

1) Turn them off.  Then turn the thermostat down to 52.  I guarantee 
that is better than either of your options.
2) The fans MIGHT keep the furnace from coming on (or they might not), 
but having the room warmer, means that it loses more heat, which is why 
you are bothering with a programmable thermostat in the first place.
3) The difference either way is negligible.  Certainly not worth the 
energy you are using to figure it out.

 > Ok, granting that the real issue here is that more insulation and
 > weatherproofing are required, let's continue instead on the issue
 > according to a case study in which the building occupants cannot
 > afford to spend any extra money on insulating and envelope work at
 > this time.

Why not continue with the REAL issue?  I am willing to bet that there 
are weatherization options open to you with a payback of less than a 
year.  That means that it would be cheaper to do them then to buy the 
(extra) fuel you use to heat the building this winter without them.  Or 
put another way, they should be what you should be doing since your 
building occupants can't afford to spend any extra money on FUEL (and 
then need to do so again next year.  and the year after that....)


Thank You Kindly,

Corwyn

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
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topher at greenfret.com
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