Q: I would like to convert our poultry houses (or pig barn or cow barn) to greenhouses for the purpose of growing tomatoes. What is the best way to do this?
A: Judging by the several conversions from poultry / pig / beef structures to greenhouses I have seen, I cannot recommend it. You are far better off starting with a structure designed as a greenhouse. The other buildings are built too heavy in support for the roof and cause too much shade, they do not ventilate properly, and won't provide the optimum environment for a high light crop like tomatoes.
I suggest you get several
quotes for greenhouses for the size you are looking for and compare them.
Several vendors are listed in the back of the Greenhouse Tomato Handbook.
See this publication and lots of other information at
Also, you should plan on coming to the Greenhouse Tomato Short Course, a national training for growers held in the Jackson, MS area.