Light Requirements & Shade Cloth

[Dimples]

Originally Posted by HiOrcDen

So good to know... should I get white SC?

White shade cloth will keep a greenhouse a lot cooler than a darker color SC. Aluminet should keep it the coolest because it reflects some of the light/heat.

Lighter colored SC can be more expensive than darker colors. Light colored plastics typically require the use of virgin raw materials to avoid a grey/off color, whereas darker colors can use post consumer materials for some of the inputs since there will be added dyes.

If you're shading an outdoor patio-type space that gets a good breeze most of the time then the SC color probably doesn't matter. If your hottest months are only in the low-mid 80s then it also probably doesn't matter. If you do want to limit any potential heat gain, choose white, tan, or aluminet if your budget allows.

Also consider what is on the other side of the setup. White and aluminet can be very bright to look at in full sun. Unhappy neighbors with a "new" glaring view of your shade cloth could outweigh the desire to avoid a few degrees of heat gain.

[HiOrcDen]

Originally Posted by Ray

Two layers of 30% shade does not equal 60%.

70% of the light passes through the first layer, and 70% of that passes through the second layer, resulting in 49% of the original, incident light passing, or 51% shade.

Originally Posted by Roberta

Consider Aluminet (made from aluminized Mylar). It provides even shade, and also reflects heat as well as light away from the growing area - I find it noticeably cooler under the Aluminet than adjoining "regular" shade cloth. And it even helps a bit in winter, reflecting ground heat back to the plants.

Originally Posted by Dimples

White shade cloth will keep a greenhouse a lot cooler than a darker color SC. Aluminet should keep it the coolest because it reflects some of the light/heat.

Lighter colored SC can be more expensive than darker colors. Light colored plastics typically require the use of virgin raw materials to avoid a grey/off color, whereas darker colors can use post consumer materials for some of the inputs since there will be added dyes.

If you're shading an outdoor patio-type space that gets a good breeze most of the time then the SC color probably doesn't matter. If your hottest months are only in the low-mid 80s then it also probably doesn't matter. If you do want to limit any potential heat gain, choose white, tan, or aluminet if your budget allows.

Also consider what is on the other side of the setup. White and aluminet can be very bright to look at in full sun. Unhappy neighbors with a "new" glaring view of your shade cloth could outweigh the desire to avoid a few degrees of heat gain.

I am going with a cheap shade for now, while I plan a setup. Thanks so much for the ideas, and pics!

This may be a curious question, but I am wondering if shade cloth will allow more light through if it's at a 45 degree angle? I am thinking the thickness of the cloth would block slightly less at the angle. I imagine it would be nominal, if at all! Is it a possibility, though?

[estación seca]

The percent shade is measured with light incidence perpendicular to the cloth, or 90 degrees from the plane of the cloth.

If the cloth is tilted 90 degrees such that the rays hit it edge-on it will allow 0% of the light through. The area shaded will be very tiny. It's hard to keep it always in that orientation, however, since the sun appears to move around in the sky.

At angles between 0 and 90 degrees the cloth provides more shade than the stated rating, and the amount is proportional to the degree of inclination from perpendicular. But the sun appears to move around in the sky, so the amount of shade provided varies slightly through the day, no matter how the cloth is positioned.

It will be less not more shady if the cloth is angled away from perpendicular, but 45 degrees won't make much difference to your plants.

Finally, you're overthinking things. Roberta's location is similar to yours. Try what she suggested.

[Ray]

At any angle other than 90-degrees, the shade cloth with block more sunlight, due to the thickness of the web occluding the openings. However, as they are relatively thin, it won’t be much.

Think of vertical window blinds as an example of a very thick shade cloth. From straight on, you can clearly see through it, but as you move to the side, the observable gaps get smaller and smaller, with the slats eventually completely blocking your view.