The antifreeze used in heating systems reduces the efficiency of the system by nearly 10 %. Yes it protects against freeze ups, but tiny leaks seem to become more numerous around/in valves, flow checks, fittings, etc. The stuff is REALLY
slippery in a heating system. As Freddie says, it REQUIRES a constant oversight to maintain the proper Ph or it goes acidic and eats up your system from the inside out, over time, if left unchecked. Kind of like the antifreeze in our vehicles. Leave it untested for years and see how the aluminum parts and gaskets like it. Tried to replace a thermostat 10 years later?
If you choose to use a 60 watt light bulb to help protect the area, better not mention it to anyone. I case you didn't know, building codes don't even allow an incandescent light bulb in a closet anymore. Gotta be a florescent now; fire hazard. Casually ask your local firemen about it. I like the separate thermostat idea or Greg's thermostatic heat tape idea. Is the loop piping pex or copper? Pex is forgiving, copper absolutely not.