Coolaroo Shade Fabric w/ UV Protection

What exactly is 90% UV protection? I installed this outside the glass on my sunroom skylights. End results, the black slate on the floor was 83 degrees in the shade, 110 deg. in the sun and 90 deg. under the shade fabric. Do the math; the shaded part is a 100% reduction at 27 deg. The part under the fabric is only a 74% reduction in heat reflection. I was hoping for 90%. Bottom line, If you are going to go through the labor of installing a sun shield why not block 99% of the heat. regular white cotton bed sheets block about 99% of the sun rays and still let in a real lot of light. Cotton obviously doesn't last and is not strong. Still searching for the right material. I am looking into sail or parachute material. I suppose if the product was used as intended, as an outside patio or deck sun shield it would be okay. As long as you are content with only blocking 75% of the HEAT! It is very strong. PS. Rather than go through the trouble of trying to return the product, I ended up doubling the Coolaroo fabric to achieve my desired results. ----------------------- Revision July 11. Installed this product over my open deck as a Sun Shield, as the product is intended for. Although I do not have test equipment to see if it is blocking 90% of UV I am certain it is blocking about 67% of the sun's heat. You can feel and see the heat blasting right through the material. It literally makes a shadow on the deck floor. The temperature on the floor, in 100% shade, was 92 degrees. Under the Sun Shade it's 106 deg., in the direct sun my deck was 146 deg. Ambient temperature was 90 deg. It's definitely cooler but it certainly could be better. 90% would be 97 degrees under the Sun Shade, not a 106. Seems like a lot of money and effort to install a product like this and only received partial results. I would not recommend this product. Do not be fooled into thinking blocking 90% of UV is the same as blocking 90% of the sun's heat, as I was.