There are many less expensive options than buying new exhaust fans and shutters. I have not purchased a new fan or louver for any of my three greenhouses but I keep my eyes open for deals,usually at farm auctions, for deals a a fraction of the new price.

There are a few tips on what you should look for when purchasing used fans. First a functional louver is important. If it is bent or sticks it will be a headache to correct. When looking for a fan I prefer one with a pulley and belt and look for a motor mount that is common to replace. Motors are more easy to find and replace this way and your fan housing will usually outlast anything else.

You can get by without an intake louver if your greenhouse isn't very tight or you you physically open a door or window at an opposing end of your greenhouse prior to turning on the fan. Motorized louvers on a thermostat sure simplify things in your absense. I'm wiring in some extra fans and another louver this spring and I find that the wire and fixture costs can be substantial too. Plan your wiring to add more extras over time(circulation fans, lights, outlets).

I use gable fans and shutters from Home Depot, lot cheaper been working 7 years now. You can add like 1/4 inch rabbit wire over the opening to keep fingers out if located low in the greenhouse.

brandond-do you have any pictures of your homemade fan box and louvers