We are having a conservatory put on the side of our house, really it is going to be the dogs room. The sun doesn't particularly stay on the area where it is being built as the side of our house keeps it mostly in the shade. It will also be access to the garage which when the dogs are left and at night we will leave the door open giving them more space, I am though still worried about it being too warm.Due to where it is being built there will not be loads of windows as it overlooks next doors fence, but, it will have a polycarbonate roof. The builder recommended a solar powered fan fitted into the roof that will extract the hot air. We will probably have it fitted even though the dogs will have access to the garage where it is cool,but I wondered if anyone has one or knows how good they are.
jane

I don't have one of these fans but I do know that our conservatory gets very hot in a very short space of time when the sun is on it.  Enough to make the large dining kitchen warm too when the adjoining door is left open so I think you will need something. 
I think they could be effective as the roof is certainly where the hottest air will head :-). Does the builder know of any show conservatories with one fitted that you could visit on a sunny day to see how effective they are?