Greenhouses need to be designed to not only capture solar energy but also adequately ventilate excess heat if temperatures get too hot.
You should always be sure you have adequate vents in the roof of your greenhouse as heat rises and you want that heat to flee.
Greenhouse roof vents function really 
well because they are located where heat gathers naturally at the peak of the roof.
If vents in the roof are not possible, ensure that you at least have a windows to two you can open.
Ideally you need to have cross ventilation therefore two windows on two sides of the greenhouse work greatest.
However you should not leave the vents or windows open at nighttime as you’ll lose any heat gain and cool your greenhouse an excessive amount of.
Which means you close the vents or windows at night and what happens 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 and your plants suffer if the night is too cool.
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