Bruce,
From my experience I would recomend the insulated PVC pipe that you run PEX inside, it has lots of different makers. I have used this and a product similar to the website that you posted on two different outdoor wood boilers that I have installed. The boiler that has the inulated pex lines, the snow will gradually melt. But the one that I used the insulated PVC on, the snow never melts away till spring.
Tim