A couple of years ago during a particularly cold winter came home to a garage full of water. Turned out the original hot water baseboard heating pipe for the top floor had about 8 feet between rooms run through an unheated attic space with no pipe insulation . Haven't had a problem since (it's insulated now!) but I do get nervous on cold days. I was thinking about running a length of heating cable, perhaps on spacers to avoid direct contact, but wonder if this is an acceptable application.