Fan Information Please

Hi, I have a 9' x 12' Farm Tec twin wall greenhouse that my DH purchased for me last spring. We have 4 roof vents that we (DH) could never figure out the solar powered opener and one door on the north end. Of course we get way to hot even during this time of year (106* on Sunday) and we are not even using it. I hope to set up around the the 21st of this month and do not want to fry my plants. I have a fan inside to circulate the air but that is not enough, not from the results last spring.

What do I need? An opening on the south end? An exhaust fan? Exhaust fans are way expensive for the size of my GH. Would just a circulation fan set in front of where we would have to remove an end panel be enough?

Any help would be greatly appreciated.........my tomatoes are getting big!!

thanks,
Joyous

IMHO, you need an exhaust fan. As a general rule, the fan should be sized in cfm equal to the volume of your GH... in other words, it should turn the air over once a minute.

Farmtek has a 12" 1050cfm exhaust fan for $165. Some plain old box fans will give you enough cfm, but they may not hold up to heavy use.

Ideally it should be oriented to pull the air across the GH the same direction as the prevailling wind, with an intake on the wall opposite the fan.

You might also need more HAF fans inside to circulate the air...there is a formula in the horizontal air flow link in the "links" thread at the top.

Hope that this helps. SB

Thanks Stressbaby, DH and I have been checking out some of the links at the top and we too think that the exhaust fan is what we need. This weekend there will be a used machinery auction at our local Mennonite auction barn and we will be checking things out before we purchase new.

Joy

Here are a couple older pictures of how I deal with heat in a small greenhouse in Florida. I had just changed over to the aluminet 50% shade cloth, it made quite a difference in heat problems and also keeps it brighter inside. It's slightly more expensive than the stuff at home depot but it seems to be holding up better than the old cloth. Notice in the one picture the galvanized fan ? Thats an attic fan in an encloser with a cheap attic shutter outside. It and the shelf and hanging roof misters were how we fought heat the first couple years. We did hit 106+ a couple times in the summer so we started working on the solution. The new shadecloth helped alot but we decided to go further.

The galvanized fan is no longer the primary fan, we went to the fancy store bought one next to it.We kept it as a back up fan and set it 5 degrees higher than the new fan. . And I now have auto opening shutters for the new fan so the windows stay closed now. I still use the shelf and hanging mist systems but now just to keep the humidity up, we went with a aquafog fog fan and it really helps. I In summer the hottest I've hit with active cooling off is 104 when it was 97+ degrees at 1 pm and with it on I stay below outside air temp.
The plants inside it now are happy plants. Some of the ones in the pictures were not as happy.

http://www.myhobbys.com/greenhouse/greenhouse.htm

edited because I can't spell worth a squat ;)

This message was edited Mar 8, 2006 6:07 PM

I use Aluminet, too. SB

Thanks for the info.........will pass it on to my hubby. Sorry for not responding sooner, stomach bug got me and had me pinned but am over it now. ;-)