The Polar Fleece fabric itself cannot be treated, so various companies have developed a “wind-stopping” membrane. This membrane is breathable material, in that it allows moisture vapour to pass through, but it will resist wind penetrating the layer.

One way, and perhaps the most effective method of windproofing a fleece, is the sandwich membrane.

This is achieved by a breathable membrane being bonded between two fleece layers.  Although this is an excellent method, the material itself feels stiffer, and perhaps does not feel as luxurious as normal polar fleece

A windproof membrane will only stop wind - it is not waterproof!!