It also depends upon what you are growing (I grow mostly orchids and cactus). If I were growing tomatoes, I wouldn't bother with shade cloth.
In California, my greenhouse didn't have shade cloth but there were big trees shading parts of it during the hottest part of the day. The orchids need the shade but the cactus need the sun.
In this greenhouse, there are no trees but the shade cloth is on just the end with the orchids. The greenhouse would stay cooler with shade cloth across the whole length but the cactus wouldn't be as happy.
Two doors, 3 ceiling vents, 3 side vents and a half dozen 6-inch size clip fans. There are misters on the orchid end on a timer set for 2 minutes every hour. On really hot days, I do spray the floor (and everything else including the cactus). If I get desperate, I have a misting fan I can plug in and hook to a water faucet. I live at 5000' in the desert. Its the high desert so no 117* days but its still pretty warm - usually a half dozen days between 100 and 105. My biggest problem is a lack of humidity and wind - my greenhouse is build to withstand 130mph - luckily that hasn't been tested but we did have 95pmh winds right after we built it. Usually the wind is between 40 and 50mph. Even in the greenhouse with misters, the humidity is often about 10% during part of the day. We've had less than 2.5 inches of rain since last March.
