New greenhouse too hot
Ok, so I built my first greenhouse and it was 10 times more work than I expected, but it's roughly finished. The problem I'm having is that it's a lot hotter than I expected. I've read that exhausting the entire air volume 1-2 times per minute should keep a greenhouse within 4-8Â° of outdoor temperature. I've estimated my greenhouse to be about 1300ftÂ³ and I'm using a 16" fan rated at 1900cfm, which means I'm changing the air about 1.5 times per minute. This should put me within 6Â° of outdoor temperature. Yet with the exhaust fan running this afternoon the greenhouse was at 89Â° while the outdoor temperature was 70Â°, which is a much bigger differential than 6Â°. Also, if I turn off the exhaust fan and open the door, the temperature stays about the same. Shouldn't the exhaust fan be having a greater effect than an open door? I know there are other methods of lowering temperature, but this makes me wonder if my exhaust fan is even working properly. It seems to be moving a lot of air, but I just don't know.
Can anyone tell me if this is to be expected, or if there is something else I should be looking at?