Wind-blocking fleece is one of those things I’m ambivalent about, along with Gore-Tex liners in boots and whether or not fluoride in the drinking water drives you insane. The idea behind it, of course, is that you can wear a fleece jacket in breezy or cool conditions without having to pull on a windshell or something like a Gore-Tex jacket. It’s a pretty good principle, and I’ve found that these products work largely as advertised, keeping you warmer than their non-wind-blocking rivals. But, there are downsides. Price is one: the Patagonia R4 goes for $215, versus around $100 for a non-wind-blocking fleece in a similar weight. The fabric itself is a little stiffer than regular fleece, although great strides have been made from the early, cardboard-like iterations. And, well, sometimes the darned things are TOO warm, that slight breeze through the fleece being just what you need!
Anyway, Gore Windstopper and Polartec Windbloc both operate with the same principle: They sandwich a very thin windproof material (Gore uses a light version of Gore-Tex; Polartec a urethane membrane) into the fleece or pile. That’s a somewhat complicated manufacturing process, hence the relatively high price of these garments (Cabela’s offers a nice-looking Windstopper fleece jacket for $140, which ain’t bad). Polartec Windbloc-ACT, on the other hand, tries to make the fleece itself as windproof as possible. Polartec claims it blocks 98 percent of the wind, so you do get a little extra ventilation. It’s also cheaper to make, so a company such as L.L. Bean can sell its ACT-based Microburst Fleece Jacket for a very reasonable $125. Personally, I’d probably get one of those before I forked over the extra $100 for the R4, although it is a very nice piece.
In either case, I don’t see any harm at all in draping a windshell over such a fleece for some extra moisture protection, although the wind-blocking fleeces are also surprisingly mist resistant.