Lilith

Air circulation is a vital and necessary part of greenhouse growing. Even in winter there needs to be a source for fresh air. Fans to circulate air are essential to the health of plants in the greenhouse, so yes I would definitely get a fan and run it 24/7.

You don't say the dimensions of your greenhouse, but as you know, heat rises and needs to be vented somehow. The heat trapped in the upper reaches of the greenhouse is called "attic heat" and can he utilized for the good in winter by installing fans that blow downward to push the heat back down to ground level and warm the plants. In summer you need to try to blow that heat out either thru ceiling vents or through your door.

The sidewalls of my greenhouse are at 12 feet and the ceiling peaks at 20ft. The attic heat above the 12 ft level can be over 120F if I don't run box fans to help dissipate it 24/7

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11/2008 Outer Banks Marathon 26.2, Kitty Hawk NC--3:50
2/2009 5 Points of Life Marathon, 26.2, Gainesville FL--4:00
4/2009 Boston Marathon, 26.2-- 4:38
10/2009 Marine Corps Marathon, DC, 26.2--457
1/2010 Houston Marathon, 26.2--3:55:09
2/2010 5 Points of Life Marathon, Gainesville--415
Halloween Day 2010 Marine Corps Marathon, DC--
2/2011--Austin TX Marathon--