Believe it or not, I only use the greenhouse from mid-march to mid-may. Otherwise, the sun heats it up too much. Even if I shaded it, it would still be too much. I open both doors all day, and an exhaust fan runs all the time, it still gets too much for the plants. I would love to do more hydroponics during the summer, but the water in the tubs gets too warm, plus the lettuce and greens all bolt.
Not sure what would eat salvia plants, I plant lots of it and nothing ever bothers mine. Maybe it is slugs or mice. You would have to bust the critter to be sure. If Jamie does build a greenhouse against your home, ventilation is key. Plus, some type of fan to stimulate wind so the seedlings grow strong. You will find it useful, I'm sure! I sure hope that elbow heals soon for you.
RE: Busy Day Planting Seedlings Before the Heatwave - by Sunscape