I don't know if the following is true but I believe it. Here's the story. When my riding group began mountian riding, we were all standard track, leather suit riders. During a week long ride, suits would get heavier and boots were always wet, eveybody's shield fogged but nobody cared or gave it much thought. Kind of "it is what it is, pass the rum". I got to know a mountain X country skier who has a small shop in Cooke City, Bill's Bike Shack. This was before anyone had an avalanche beacon so we we renting them from him. He could not believe we were still wearing cotton and laughed out loud at our leather suits. I started listening to him and his explanations of moisture and core heat management and soon after began shopping for Gortex clothing that would work on a sled. I purchased a jacket, bibs and 200 weight fleece midlayer from MEC, a X country specialty supplier in Canada. The gortex shell and bib pants were designed for mountain climbing so of course I was the laughing stock of the group but that suit worked. On each trip to Cooke City, we would ride to Top of the World. It's 35 miles of groomed very fast riding. WOT corners but you have to work at it. For those of you who know the area, we would stay on the road until we reached the clubhouse, then go south in the meadows and finally stop on the shore of a small lake. Smoke break. I was always soaked and heated when we arrived and I always ended up with a chill from that break. The first time I did that ride wearing the new geek suit (as it came to be called by my friends), I arrived dry, enjoyed the break and did not get chilled. Proved to me I was on the right track. Looked very geeky but I was finally dry. Interesting that my fogging issues were greatly reduced. So heres my theory. I ended up believing that all the moisture generated by riding needs to get out and if you are wearing a suit that does not breath, it will try to get out through the neck hole of your suit. And in the process, it will expose your eyewear to a whole bunch of moisture. So, IMO, the solution is in using the right equipment. Manage all the moisture generated by wearing the right stuff like gortex Klim, open pit and back vents on your outer layer to really increase the drying effect and you will minimize the fogging of your eyewear. Then use the available technologies to deal with whats left, like fan googles. One more thing. Whatever you do, don't wear cotton. Hope this helps you. Good luck.