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I have expanded steel mesh that I use to make garden cages:

enter image description here

I would like to know how much sunlight the mesh blocks.

I think I need to calculate the area that the mesh takes up (per square inch) and then from there I could calculate a percentage of sunlight blocked.

How can I calculate the area of the mesh?

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  • $\begingroup$ If i understand the question, then you have to specify how far lies the background. $\endgroup$
    – user14407
    Commented May 26, 2019 at 20:07
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    $\begingroup$ Because it's specifically sunlight, you can approximate as a parallel rays light source making the distance to object no longer relevant. The angle of the mesh relative to the sun does matter though, as does the thickness of the wires $\endgroup$
    – Jonathan R Swift
    Commented May 26, 2019 at 21:23

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The occlusion of your mesh is the ratio between the area occluded by a solid plate of the same mass (and thickness) and the area covered by your mesh (which you can measure).

$Occlusion = \dfrac{m/(t \cdot p)}{(l \cdot h)}$

Where:

$m$ = mass of your mesh

$t$ = thickness of your mesh

$p$ = density of your mesh (steel being 8050kg/m^3)

$l$ and $h$ = length and height of your mesh

Obviously only works on mesh manufactured by slitting and expanding, it doesn't hold for punched mesh.

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  • $\begingroup$ This is a great formula, but only true if the sunlight is perpendicular to the mesh... $\endgroup$
    – Jonathan R Swift
    Commented May 31, 2019 at 15:57
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Every 1/2 of an inch you have two slats. You need to measure the horizontal thickness of an slat. by eye balling the tape it looks like 1/8th of inch.

The area the mesh masks is 12*2*2*height* thickness of the slats per each foot of the length of the mesh.

This needs to be subtracted by the 1/2 area of intersection to eliminate the overlap, if you want to be exact.

The area lighted per lineal foot length of the mesh is 1* height of the mesh subtracted by the masked area. Or if you divide the masked area by the area of each lineal foot of the mesh you get the percentage of the light masked.

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Why not calc the area of one (2 triangles) of the open areas and knowing the triangle count per screen total area you have it!

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