Where to position fans in greenhouse?

[Snaglpus]

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.

[Hershell]

Typically HAF are used only when the houses are closed and they are used to help keep mold and mildew from starting and to keep warm air moved through out the GH. One is usually placed in front of the heater and one on the other side pointing in the other direction to keep air rotating inside the house. When the ventilation fans come on the horizontal air flow fans go off.

[hoosierbanana]

I used 60% shade one season rather than the exhaust fan and the plants were not that great. Huge leaves and long thin branches.