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 escape.
Greenhouse roof vents Greenhouse Auto Vent function really well as they are located where hot air gathers naturally at the peak of the roof.
If vents in the roof are not possible, make sure to at least have a screen to two you can open.
Ideally you need to have cross ventilation therefore two windows on two sides of the greenhouse work best.
However you should not leave the vents or windows open at nighttime as you’ll lose any kind of heat gain and cool your greenhouse too much.
And that means you close the vents or windows during the night and what happens another morning: you forget! Right now your greenhouse overheats and if you’re unlucky, you lose some plants.
Or you forget to close the vents at nighttime and your plants suffer if the night time is too cool.