Trent-Lion writes in article dated Tue, 02 Dec 2003 13:31:09 -0500:
I am restoring a 15 x 10 ft. greenhouse in north FL--twinwall
polycarbonate on aluminum frame set on a 3-foot wall. GH is attached to
a small concrete block shed. It will have two exhaust fans, ceiling
fan, 4 vents in the wall, possibly a louvered window in the door to the
shed.

Most people seem to use fans in summer, heaters in winter. I have not
read much about air conditioners in greenhouses and wonder why.
Outrageous electric bills? I am considering installing an electric
reverse-cycle air conditioner/heater in the GH wall. Is this
sensible/practical? Thanks.

Fans are better than AC because they are cheaper to run and also ventillate
the greenhouse. Growing plants use up the carbon dioxide in the air, so you
need to plan a way to replenish it. Fans are the most popular method, but
you could also use an alcohol lamp, compressed CO2, or live animals to
provide for your plants. (Caution: too much CO2 is toxic to both plants and
animals.)

For the guy who suggested an evaporative cooler, I think FL is too humid for
that. But I've been wrong before.

-- spud_demon -at- thundermaker.net
The above may not (yet) represent the opinions of my employer.