I'm planning to put a shade cloth on my greenhouse. It will be exterior, hubby is making the frame for it. It will extend past the greenhouse to my "holding area" where I keep potted plants until they go out to the garden. So the frame will extend from the peek of the greenhouse out to about 6 feet high (on posts). Finished frame will be about 20' x 20' and I'll probably go with an 18' x 18' shade cloth.

I'm planning to use it from about July thru August (hottest part of the summer). By that time I'm using my greenhouse mainly for propagation and perennial starts. I have triple pane poly on the greenhouse.

The hope is that the shade cloth will provide a little protection to keep stuff from frying and maybe allow the fans to run a little less often.

I do plan to take the shade cloth down during the off season to help preserve the material (our winters can be pretty harsh)

So, my question is, what % shade cloth should I go with?

Are there any other considerations I should be thinking of?