If you think its getting too hot in the greenhouse, and the plants are getting scorched, you could use shading.
There is a product called Coolglass (I think) which is painted on the greenhouse glass to create shade.
We use fleece to shade the plants in the greenhouse, fixed in the eaves with clips Much easier to put in, and doesn't need washing off, Also, if there's a bit of a breeze, with all the windows, vents and doors open, acts as a bit of a fan.
valmarg