JulieS2, exactly, and why I never shade the greenhouse these days it is a waste of time and money. Being retired I am always about so "if and when" we get a scorching day I can simply open every vent wet the flags and gravel then drape some net or even put a couple of loose plywood boards in position to shade the plants and having a fan I put it on fast blow. Never had scorch on plants and tomato's love the sun, I keep them what I call finger damp not soaking, dip a finger in if it comes out with a bit of soil stuck to it well and good if it comes out muddy not good and if it comes out clean as it went in well very not good. Bottomless pots on gravel I find best, you water the gravel and every couple of weeks top up the pot with more compost. When everyone around me lost their tomato's to blight mine were OK.
All this is from my own experience over many years others do things in a different way, there are no right or wrong ways it is what suits you and the way you garden, when I was working all day I did things in a different way.