You're also going to need a shade cloth. I don't have exhaust fans in my GHs. I remove the plants to the semi-shady front porch or the sunny deck on the west side of the house.

Man, I'm getting impatient about not being able to look up old threads!

If you're asking about HAF fans (for horizontal air flow) and not exhaust fans, I am using two oscillating fans for air flow, and both run 24/7.

One is an 18" wall mount oscillating fan (SMC brand) I bought at Kmart for $40. We mounted it high over the doors. I don't know how long it will last (so far six months.) Several of the greenhouse supply sites have high quality hanging or wall mount HAF fans designed for GH use, but they cost a lot, so I thought I'd try this first. It has a remote control to turn it on and off, or to change the speeds, which is really handy since it's up high. It has three speeds.

I also have a small 10" oscillating table top fan sitting on a shelf at the other end of the GH. This one is annoying since I can't position it so it doesn't blow right on the plants sitting next to it on the shelf. None of my plants like the windy spot next to the fan, they all get very dried out. I may try eliminating that fan to see what happens. I can see why hanging or wall mount fans are better.

For cooling, I have a 16" exhaust fan on a thermostat. It only kicks on when it reaches the temp I set the thermostat to, so it only runs during the hottest part of the day (and not at all this time of year.) I bought the thermostat at kkontrols.com, and I bought the fan at ACF Greenhouses. I haven't bought the shutter vents that are normally used with an exhaust fan because I planned to use screen doors instead for the air intake. Right now I just open the doors (my screen doors are still on the "to do" list.)

Pelicanhead,
After looking at the options for my greenhouse, I decided to try the Farm Tec 10" utility exhaust fan ($89). www.growerssupply.com
It has worked well for the past year, when a thermostat was added, and comes with shutter vents as part of the assembly. It has a relatively low output (350 cfm), but helps on very hot days.

Here is mine it works great. Beats the hell out of HAF fans

Here is a link that might be useful: {{gwi:287904}}

Gardenerwantabe, That looks like it might work. So then what does the fan in the background do?

Posted by pelicanhead 10 southern Ca (My Page) on Tue, Jan 29, 08 at 20:23

Gardenerwantabe, That looks like it might work. So then what does the fan in the background do?

IT IS A 16 INCH EXHAUST FAN
The ceiling fan is 52 inch it moves more air than a small HAF fan but it don't make all the noise.
Magnetic drive motor uses far less power to run than a HAF

Gardenerwantabe,

So then do you have a vent on the other side of the greenhouse over the door? And do you use the vents in the roof? Someone here doesn't use the vents, I can't remember if it is you.
Carlyn

I have my vents locked down and a pool cover permanently secured to the roof where no air can get under it and blow it off.
Last night the temperature dropped 40 degrees and the wind was recorded at 80 mph.
No damage to the GH and the pool cover is OK also.

After reading about all the problems people had trying to keep their pool cover tied on I decided their had to be a better way of doing it.

The exhaust fan is controlled by a thermostat and their is a electronic vent over the door in the front