I agree to some extent. My greenhouse is polycarb with no built in shading.
I live in SC and find that 2 layers of shade on the poly provide the degree
of fine tuning I like. I run 20% shade on the bottom layer and 50% shade on
the top for 1/2 and 20% on the top for the other half. The layers can be
rolled up to any level to accomodate the plants underneath for any season.
Right now, I have all shade off the vanda-dendrobium, tropical shrub area;
20% on the cattleya area; and 50% on the phal-paph area. As the sun angle
decreases, more sun gets to the the 50% area making it basically 20% for the
months of Nov-Jan.
So basically I'd say, it depends what you're growing, where you're growing,
and how much you're growing as to whether or not you can partially shade
your greenhouse in sections to suit your needs.
Gary

"Pat Brennan" wrote in message
...
Not being from Fla I was not going to respond, but after surveying the
sunburn damage I did last week while changing the plastic on one of my
greenhouses I thought I would chime in. Here in Va the peak summer sun is
about 10,500 foot candles while the peak in the winter is around 8,500.
Assuming it is similar down there (I have no idea) and given that you were
running 60% shade, your summer light levels peaked at about 4200 foot
candles. If you remove the 50% shade cloth your winter levels would peak
at
6800 foot candles. That's a pretty big increase (62%), some plants might
love it but it will burn others right up. Do you have enough plants that
will love it to shade the rest? With sunburn you can do permanent leave
damage pretty quickly and too much light will stress a plant over the
winter
even if you do not burn the leaves. I increase light levels no more than
20% to 30% in the winter. Too bad it wasn't 50% polycarb and 20% shade
cloth cause then it would work great.

Pat


"bb" wrote in message
...
Ok, do you folks in Florida remove your shade cloth this time of year?

I have 50% cloth on top of 20% polycarb panels. It did a wonderful
job of shading and bringing the temps down, but now I wonder if it
should come off 'til spring. Opinions appreciated.

bb