Lori, the first thing we did was use cheap netting over the vents. We had mice or squirrels that ate big holes in the mesh in order to get into the GH. I also had some plants outside protected with wood cages covered in the netting, and they ate their way into those. Little monsters!
My 1st post in this thread just appeared in the mid-winter addition of the Hobby Greenhouse Organization's Newsletter with our forum url below the article.
Hopefully, some members will notice the url and try our forum out.