My greenhouse is near some fruit trees and every spring when I come to start off the growing season I find a certain amount of grime has settled across the glass over the preceding year.

Most years I give it a thorough clean and it looks much better for it. This year I didn't bother but how much does it matter?

To be more accurate about the extent of the grime ... it's certainly more than any normal houseproud person would tolerate on their kitchen windows, but it's not enough to feel as if any serious amount of sunlight is being screened out. But, maybe I'm mistaken about that, hence my question.


It depends what you want to accomplish. The grime can be beneficial or detrimental depending on your goals.


Reduced light transmission - good if your plants need reduced intensity sunlight

Increased insulation (at least in theory)


Reduced light transmission - some plants may not be getting optimal light

Unsightly - the asthetic is off

Ultimately, it depends on what you are growing. There is no hard and fast rule about what to do. If your plants are happy and you are ok with the appearance, leave it.

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