Greenhouses need to be designed to not only capture solar energy but also adequately ventilate extra heat if temperatures get too hot.
You should always make sure you have sufficient vents in the roof of your greenhouse as heat rises and you want 
that heat to flee.
Greenhouse roof vents function really well as they are located where heat gathers naturally at the peak of the roof.
If vents in the roof aren’t Greenhouse Auto Vent possible, ensure that you at least have a windowpane to two you may open.
Ideally you need to have cross ventilation therefore two windows upon two sides of the greenhouse work best.
However you shouldn’t leave the vents or windows open at nighttime as you’ll lose any kind of heat gain and cool your greenhouse too much.
Which means you close the vents or windows at night and what occurs another morning: you forget! Today your greenhouse overheats and if you’re unlucky, you lose some plants.
Or you forget to close the vents at nighttime as well as your vegetation suffer if the night time is too cool.