Greenhouse shading?

[Brengirl]

I have a partially glazed, roof and windows, shed. It is leanto to a garage wall. It's get so very hot inside that I am attempting to put up some removable shading. I also have an extractor fan. Does shading reduce the light to the detriment of the plants. Which is worst, too hot or too shady?

[FionaH]

I moved this out of growing techniques so people can see it!