Good day, I have a question for my greenhouse folks.  A few weeks ago, I purchased a new GH.  It came from Northern Tool and Equipment.  The one I bought was the heavy duty 12'x20'.  Here is a picture of it from their website.

http://www.northerntool.com/shop/tools/product_200596452_200596452?utm_source=CSE&utm_medium=Google&utm_campaign=Lawn%20%2B%20Garden%20%3E%20Green%20Houses&utm_content=31758&ci_src=17588969&ci_sku=31758&gclid=CjwKEAjwvbGqBRCs3eH4o5C74CYSJAB3TODsnHFIu5ujXFAPYNigfUK7TKTKw-zisSMlYBCx0-BLxRoCu0Tw_wcB

The GH is 95% complete.  All I have to do is place the main top on and BOOM, done!  I haven't placed the top on yet because I haven't dug my trench for electricity.  That will be done this weekend.  My plan is to place 2 pedestal fans inside to help circulate the inside air.  I have the fans ready to go.  They are theromstatically controlled.  But my main question is where to place them?  Should I place them in opposite corners?  And will 2 fans be enough to keep the unit cool?  I also have 70% shade cloth going on top this weekend too.  Thanks in advance.

Place them where convenient. You have two options, direct impact on plants or whole system movement. Direct would be aimed at certain plants, whole system would place each fan 1/3rd in aimed in the same direction to get the entire air system moving. I am not sure two oscillating fans will be enough in that big of a greenhouse to get the entire system moving, so direct may be your best bet.

I'm not Hershell and the link won't open for me.  In general you want to blow air from low and outside the greenhouse up to the top and then out from the top to a vent or a door.  A circular pattern with some air blowing out would be second best.

I have two 25 foot long houses. up high blowing out and i have 1 foot sqare windows along very bottom and leave them open. It pulls air from outside across plants and sucks hot air that rises out. Most professional bulit houses i have been in have fan up high blowing out. If i was going to build my own green house. Back wall would be intake and front wall exhaust fan blowing out. Luke a paint spray booth if you ever seen one. Full hot air to cool air exchange

I assumed this was secondary circulation in addition to an exhaust fan. If not, rcantor is spot on!

I doubt 2 fans is enough and I'm concerned that 70% will cause it to be too dark for optimum plant growth.  My assumption was that the greenhouse is not robust enough for fans near the peak.

cool high tunnel Dennis

how will you anchor it ?


WERE DOES THE REALY BIG FLAT SCREEN GO ?  ;)

Dennis did you see this you can probably add a nice small electric fan to this 

It depends on why you are using fans. If you are removing heat, put the at the top. If you want even temps, you need to orient them to provide good circulation, either pushing cold air up, or warm air down.

And to give you an idea, I have my oscillating fan at one end of my greenhouse and can feel it only 4ft away.