I tried those.. and yes as long as you were moving they were ok.. not great.. but as soon as you had to stop you would fog.. and it also would depend on the intensity.. if you had to climb anything steep enough to slow you down while increasing you heat output.. it would again fog.. not everybody is going to drop the dime for a set of goggles with a fan.. but for those tired of whiping crap in the lens every ride or those that are tired of fogging as soon as you stop or slow down enough to not have enough air movement with a passive system to keep up.. the active system is awesome.. I will never go back.. I can do ints in these and still walk in the house with them on afterwards and never fog.. you just cant beat that with any passive system without letting a lot of cold air all over the eyeballs..