I work in a very large warehouse with very high ceilings.  There are
ceiling fans that hang down about 3 to 4 feet.  My boss does not turn
them on in the summer when it is 85+ degrees because he claims all
they do is force the hot air that is at the ceiling down and this
causes the fans to actually heat the area instead of cooling it.  I
thought the point of ceiling fans was to move all the air.  I would rather
have moving hot air than stagnant hot air.  Who's right?

Depends on why the fans were installed - do they pull air up or blow air down?

If they blow air down then while they are useful in winter to move the
warm air down to ground level, they will be less useful in summer. And
if your warehouse has "very high" ceilings the stratification of the
air means that the air next to the roof will be quite a lot warmer
than air at ground level. They're not a substitute for proper
ventilation and/or cooling.

The blades are tilted, look at them as they turn, which way are they
going? Look for a reverse switch which reverses the direction the
blades turn. In summer, they will "scoop" the air UP, causing the
cooler air to displace the hot air at the top, in the winter, the
blades force the warmer ceiling air down.

Blow down ceiling fans help warm the floor, which generally is not
desirable in summer. Ceiling fans that blow up have little utility
unless other than cooling the ceiling. Horizontal blowing fans are
best in summer in my opinion. A fan, close to the floor, in a doorway,
aimed up slightly, will sweep up cold air near the floor in one room
and mix it with the warmer air in the other room. High ceilings
generally are less comfortable and more costly, both initial and long
term.   Neil

This is an interesting, complex problem. Your boss may be technically
correct about how the fans distribute heat. But on the other hand, you
certainly ought to know which circumstance you find more agreeable;
moving hot air vs stagnant hot air. Perhaps you could ask for an
experiment, to see if you & your peers generally prefer moving hot
air.

Moving hot air is no picnic.  A few weeks ago it was about 100 degrees
in New York.  The "canyon" effect in Midtown made some intersections
windy.  The humid hot air hitting you was no fun at all.

"Moving hot air is no picnic."

   I'm sure that you know how uncomfortable you find hot, moving air
to be. But the OP also knows the same information concerning itself.
It may be that cath12 really does find hot, moving air to be the
lesser of two evils.

Thanks, everyone!  You are right, qed100-ga -- it is the lesser of two
evils.  I wouldn't wish either on anyone.  I too, am in NY but these
fans would not create wind but they would create a breeze.  When
sweating (ew), any breeze feels better on the skin.

My boss also does something else:  In the main showroom of our carpet
business, he has a window air conditioner.  I keep pointing the
louvers (sp) up toward the 9-foot ceilings (no ceiling fans involved).
 He gets upset and says they should be pointed toward the floor. 
About six feet in front of the A/C is a carpet display (basically a
wall) and that's what I think he is cooling, along with the floor.  My
desk is about 20 feet away, on the other side of the display.  I can
feel the A/C with the louvers pointed up but feel absolutely nothing
when he points them toward the floor.  Isn't he wasting energy ding
this?  How does the whole "cold air falls" fit into this.  He says we
should be keeping all the hot air at the ceiling.

Any comments on this would be appreciated.

Cath12

I want to add that the window A/C is only about a foot off the ground
and the louvers are about 3 feet off the ground.

I think once again the situation in the office reduces to which
arrangement you find more comfortable. It hardly makes sense to me to
even have air conditioning if you aren't benefiting from it. Even if
it's demonstrable that louvers down is better than no AC at all, you
still know that you only feel *adequately* comfortable with louvers
up. As long as there's no prohibitive cost involved, it should be
whichever way people need it to be.

I would think that the blowers are forcing the cold air upward.  Once
the air has slowed it then begins to sink.  You are probably in the
path of the falling cooler air.  The downward setting probably causes
the cool air to lose its velocity on striking the ground and it warms
as it creeps over the hot floor.  By the time it reaches you it has
warmed enough that you can't tell the difference.

I think you are right. When ceiling fans moves, it causes the air(even
it is hot) blowing. And thus it quickens the vaporization of all that
contains water, such as our skins. And so we feel cooler. BTW, the
temperature distribution varies little even in a very high warehouse.

there are certain ground facts

1) ceiling fans, do not lower temperature under any circumstances, but
increase due to the motor working, still we feel the effect of a fan
as cooling

2) circulation of air is what it does, so even when it is when it is
85+ degrees or 4 degrees sub, what it does is circulate the air,


Keeping this fact in mind 

what does the fan do??

it cirulates or cycles the air, there by causing a drift of well
circulated air to equally distribute the temperature in the room, when
it is 85 degree plus it circulates air for better dissipation of heat,
making the room cooler ( feel cooler) it also provides a better
ventilation method for high ceiling buildings,
coz it prevents the hot air from stuck up the roof and making the room
more humid and unbearable, it makes the air move, and at a passage the
hot air might even move out of the room (windows or ventilations).


Please ask your boss to turn the fan on, and about who's right ..

You are absolutely... :)

This is a very interesting thread.  I am an architect and remember my
heating and ventilation professor explaining, emphatically, that a
ceiling fan can never blow heat down (in the winter) that in fact the
effect is more of a cooling effect, as in summer, the breeze across
the skin has a cooling effect. Weather in a warehouse or a small
bedroom, a fan has a cooling effect.  This is the reason that if one
uses a fan in the cold winter months, it is operated in a fashion that
it blows UP instead of down, thus circulating the air, alas not the
heat!.  For 20 years now I have been telling people not to use fans to
distribute heat in the winter. I started searching for a confirmation
of this and found this thread. Can anyone confirm or deny this claim?

wind ;;;

is an amazing phenomenon, caused by rise of hot air up the atmosphere,
coz the air immediately above earth gets heated up first,

now if hot air is moving up, the heat is also technically moving upso
circulation even if it is air,
(in reality) the temperature also does get circulated...

so there is no question that it helps in better circultaion of air and
thereby temperature,,


Fans never blow air up (atleast not ceiling fans) coz any one standing
right below can understand where it is forcing the air, but yes air
does move up... that is to fill the vacuum created by air that moved
down, by the push of the fan... and this air is from the side part of
the fan..


So technically who's right? it is hard to say, but we come together at
one point, fans do move  air and that circulates temperature well (you
can take the convection heat transmission method in fluids, where the
hot fluid exhanges heat to the cold part in the fluid, infact air is
also fluid matter)

                      :) :) :) :) :) :) :)

Hey Cath 12,

What u need is a way for the hot air to escape. Easiest way would be
to open up an exhaust in the ceiling of your warehouse. You can also
have a force exhaust fan installed.
The hot air going our will be replaced by cooler air coming in. You
can have various arrangements to increase efficiency like opening
doors on the west side during mornings and on the east side in the
afternoon.

You can attach thin strips of paper at different overhangs to observe
the airflow patterns and experiment with opening / closing different
doors for best effect.

Once the airflow starts then evaporative cooling on your skin will
make working in warehouse more bearable.

good luck

As an engineer in a production warehouse in south Texas, I can tell
you that I feel for you.  If you're in a typical steel building, the
air at the top will be stifling during most of the day (however, it'll
cool off at night if you're in a 24-hour facility).  As such, fans
won't make much of a difference.  They will circulate the air, but it
can heat it up to heat-stroke levels.  The exception is if there are
vents near the ceiling, allowing cooler outside air to be pulled in by
the fans.