Kathy, my roof does not have a vent. I have a really strong fan high up on the South wall vented to the outside. It is connected to a thermostat. Works very well.
Not sure what you mean about UV screening on the inside? I shade the greenhouse in Summer by installing Aluminet into the ceiling. I could never do that in a full greenhouse, the way I have set that up with bars attached below the ceiling and threading the panels through that, I only use that in Summer, when all the plants are outside.
I don't need any other screen, I want as much light as possible in Winter. I would have to look it up on florian's website, they list the types of glass they are using, I don't remember exactly which one we have , but it does cut some light. ( My transition lenses still get dark in the greenhouse!
)
Florian offered one time to mount a retractable awning outside over the greenhouse, to be opened and closed with a push of a button. If I ever keep my Orchids in the greenhouse over the Summer I would probably consider that. But, if they have nowadays a better solution for hot Summer days, that might be even better.
