Greenhouses and hot weather

[GemmaD]

Hello,
I have a troop of juvenile Greek Spur Thighs who have been kept on a tortoise table in the house up until now. We've just finished constructing a greenhouse for them to live in, the next plan is to add on an outside run to it but we haven't quite got there yet. I was wondering if anyone has any advice about keeping them in the greenhouse before they have access to an outside area - will it be too hot for them? Should I wait until they have the option of escaping? We have an automatic roof vent but it can get very hot in there, especially in this weather! Ideally I'd like them to go into the greenhouse but not if it's bad for them.
Thanks for your help,
Gemma