Roof clearer

I have been using BEST rubber roof cleaner.. Very easy. Handle brush it it on ..like your washing the TC...and wash it off with the hose. Roof is left white and protected foe six months. It's called B.E.S.T. Use it on the vents too.. Gently

It might work if you use a light hand . I would try it on a small area in a corner and see how it goes .

I heard of someone who did that but used a little too much elbow grease, cracked it and had to replace it.
The uv also makes the vent brittle. I think most people just live with it becoming hazed over.
You might be able to protect a new vent or an older cleaned vent by using some kind of uv inhibitor. Maybe ProtectALL would work ? It says it can used for uv on plastics and all surfaces.

I took this from a uv link re: plastics ......

"
DuPontTM’s Light Stabilizer 210 uses extremely small particles of titanium dioxide (TiO2) to efficiently absorb ultraviolet light, protecting plastic and anything it covers from the sun's damaging rays. This is the first in a family of products based on breakthrough DuPont titanium dioxide process technology. It is an additive designed for use in plastics to help protect products from cracking, fading and other types of solar degradation. Potential applications include sporting goods, outdoor furniture, fabrics and carpet fibers - virtually any plastic product that will be exposed to sunlight. It also can be used in plastic films and sheeting to protect plants in greenhouses or packaged goods from UV light. In testing, this product blocked twice as much ultraviolet light as several classes of competitive products. It works by absorbing ultraviolet rays and changing them into small amounts of heat which dissipate quickly without damaging the structure of plastic. The key performance advantage of the new light stabilizer is that its extremely small particle size provides much more surface area for UV absorption ".

UV has clouded up my bathroom skylight. I was wondering about the stuff being sold to uncloud car headlight lenses to clear it up.

depends on the roof .
edpm , rubber roof i always avoided cleaning with petroleum distillates in the product, it can harm the glue that bonds it . http://www.campingworld.com/shopping/product/dicor-ready-to-use-rubber-roof-cleaner/5774&affiliateid=3184
i always used a rubber roof uv protectant to finish the job.

TPO roof is easier . mild soap n water .

here is a roof cleaning link
http://www.rv.net/forum/Index.cfm/fuseaction/thread/tid/25340316/gotomsg/25340907.cfm