do most of the mold/pm problems occur from................?

i started putting my plants inside the shed at night along with the proper ventaliation of course and havent seen any signs of mold or pm that has destroyed plants in the past, so i was wondering if its the night time temps that cause the mold/powder mildew? with them being in the shed its at least 5-10 degree warmer..........thanks

Humidity and low ventilation do the trick for me, recipe for a disaster.

High humidity and low air circulation,,there's white and black mould in the air all the time if you give it a nice humid place with no ait circulation it will settle on a surface , you get it on dry curing sausages , its the black stuff that's poison, plenty ciculation to stop it from settling