Do a size, material take off , design and cost first. It's not cheap. Between the glycol, 2" foam board underneath AND sides, pipe, exchanger big enough, mixing valve PROPERLY sized and manifolds. Most stop right there. Do it right or you'll have problems like mentioned above from doing it wrong. Expensive mistake. You also need to factor in drainage or ice dams will be an issue. If setup correct you will melt the snow before it ever accumulates. Systems are designed to turn on at the very first flake, if you turn it on after even a half inch has accumulated it quadruples the time and heat needed to melt the slab. Some systems idle when temp is below freezing and humidity is above a set point. This is how you will use the least energy and clear the slab the quickest. Viega, uponor have articles and how to design PDF's online. Good luck, pre planning prevents poor projects