Hi
@Howie74 and
to the group.
I tend to agree with
@Henderman. It's not a hot roof that is creating heat in the greenhouse; it is the sun passing through the skin of the greenhouse, warming the plants, fixtures, flooring materials, air, etc. and becoming trapped inside the greenhouse that is creating the heat. Spraying the roof with water will only decrease the amount of trapped heat insofar as it's ability to reduce/deflect the amount of sunlight passing through the roof, which will be just about negligible. You would be much better off concentrating on shading and air movement systems.
