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A lot of small greenhouses seem to have this green/clear mesh plastic covering on them like the picture below and I wonder how these compare with similar houses that don't have the plastic weaving in them.

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In the back of my mind I have latched onto something that an expert said to me once - "One percent more light is one percent more growth". While this is intuitive, I need to question how true this statement is.

For herbs and edibles typically grown as annuals, does anyone have an idea as to how this kind of plastic mesh compares with the clear plastic meshes? (Bonus if anyone can comment on the truth of my 1% more light = 1% more growth belief)

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  • How could 1% more light = 1% more growth be wrong for sun hogs? But some houses use shade cloth, so less light is good for some. Commented Feb 22 at 22:07
  • @YosefBaskin I'm with you - but I was talking to a friend who immediately questioned that assertion. (Unfortunately not with facts - but it did bring back to me that I had accepted the statement unquestioningly because I knew nothing and it came from an someone I considered an expert).
    – davidgo
    Commented Feb 22 at 22:18
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    I believe the mesh is a type of rip-stop, preventing a small rip from becoming a major problem.
    – Jurp
    Commented Feb 22 at 23:29
  • There are versions with a clearer reenforcement mesh, too. As always, many tradeoffs between durability and light transmission and expense and... I can say I got more than the rated years of service from 4mil UV/IR treated unreenforced plastic. But if you have excessive wind exposure or branches tend to drop on your greenhouse this sort of thing might help, or might be overwhelmed by the insult to it, depending.
    – Ecnerwal
    Commented Feb 23 at 0:27
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    @davidgo Regarding "1% more light = 1% more growth", that is roughly true up to a point where you get diminishing returns, and eventually more light diminishes growth. The photosynthesis-irradiance (PI) curve gives an idea what this looks like, you can find research on specific plants to put numbers on it.
    – MackM
    Commented Feb 23 at 18:24

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After erecting this greenhouse, I have now taken some very rough measurements using a light meter on my cellphone. This cloth seems to block about 30% of the light (ie taking readings inside the greenhouse and then immediately outside of it.

As a relevant aside, when I took readings with the sensor facing directly at the sun, it was to bright to read outside, however it provided readings inside - so there is probably some level of diffusion going on. (This makes perfect sense as looking from the greeenhouse out, everything looks blurred)

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