A Silkies feather is a real feather....LOL
The only difference between a Silkie's feathers and a normal feather is that the Silkie doesn't have barbicels between the individual hairs on the feather shaft. The barbicels are little "Hooks" made out of a ligament like material that hold the feathers shape. If you've ever held a feather and separated the hairs, when you run your finger back up the shaft of the feather you can "stick" the hairs back together. Its because normal feathers have the barbicels between each hair.
Other than the lack of barbicels, a Silkies feather functions the same as any other birds feathers. Like Silkiechick said, they do soak up water faster than normal birds, water doesn't bead up and run off like some. But it functions the same way when it comes to keeping the bird warm. Do the same thing with your Silkies that you would with any other bird.
Block the wind, heat lamp in extreme freezes, and keep their water from freezing.