Hey,
I have a very simple, makeshift greenhouse and I'm quickly noticing I need a vent. I'm wanting to make it simple and passive. The structure is a small wooden building with construction plastic. So far I've been thinking of cutting a hole and making a flap I can open during the day.
Also, if your reading this and haven't thought of making a greenhouse mine is very simply and cheaply made with recycled 2x4's cut in half (to make two 2x2's) and cheap construction grade plastic that has helped germinate some healthy, strong plants quicker than I ever predicted.
Thanks in advance for any input!
If you want to improve air circulation it is better not just to add a vent but to allow air to circulate. Put vents on opposite ends of the green house. one one vent put a fan blowing in and on the other put a fan in reverse. if you don't use fans you can put screens on both ends of the greenhouse to exclude pests and plastic flaps to close when it gets cold. It is better to have some kind of roof vent to let out the hot air. This is best done passively with an off set roof design that allows hot air to rise out and pull air in from the side vent below. Usually you have a system of windows to make the roof vent. You need to be able to open and close the roof vent as needed and screening to keep birds and other things from coming in. If you use a wax piston, it does not need electricity but depends on the melting and cooling of wax in the piston to operate the mechanism