Great article! My greenhouse is a little larger than a hobby greenhouse at 1730 sq feet. But all of the things you address are true no matter what the size. My greenhouse was built for me by people who mainly build them for agricultural purposes, so mine was considered 'small' to them. Here where I live, you could almost have a shade house like in South FL if not for the fact that we do get significantly colder temps for significantly more nights in our pretty short winter. But a screen house would be almost perfect here for 9+ months out of the year.
Mine was built in 2003 so stuff is starting to get old and that means it may be possible for me to make some changes when new things become necessary. Right now, I have 4 HAF (high air flow) fixed mounted fans at the level of 12 feet (of a 12-20 ft roof slope). These come on automatically depending on when the thermostat thinks they need to, based on what I set it on. They really do move a lot of air in the attic, and you can feel it on the ground as well.
But my major cooling force are two 4ft x4ft exhaust fans in front that pull air through a 36ft vent at the back which is covered with honeycomb. The original purpose of the honeycomb was to create a swamp cooler. Water can be recirculated through the pads and when the air is pulled through it cools it. But, here in this climate, the swamp cooler really did not contribute that much to cooling. What it did was create even more humidity in an environment that, most of the year, is already at 65%-100% humidity to begin with. So I turned off the water to the pad years ago.
I have wondered about the feasibility of replacing the honeycomb with something else. Something like screening that would allow a lot more air flow through. The honeycomb is about 4" thick. Replacing it with a screen, even something like small square chicken wire, would allow a lot more air through. But I wonder about heat retention then in winter. The honeycomb serves as a big insulator when the vent is closed.
In the past, I have also sometimes had additional fans (four inexpensive Home Depot box fans) that I hung up in the rafters at the 12 foot level and positioned to blow air in a circle and slightly downward. I may replace these this summer, I'm not sure. They worked well, but I had a lot of vines that kept growing up in and through them and causing problems. I have removed the vines now and there would be more unobstructed air flow.
@MoonShadows, what do you think of these ideas?
