I plan on running PEX pipes both hot and cold across 16 feet of unheated attic space above a foyer. The foyer is 16' long and is off the kitchen, it isn't heated directly but is part of the house; it is usually colder than the rest of the house, mostly due to the cat door and slider the dogs go in and out of. There is insulation along the ceiling, underneath where I will be running the pipes.
What is the best way to keep the pipes from freezing? Would an insulation pipe jacket be enough to keep the water in it from freezing or should I also run a long heating cable? I also considered insulating along the roof but it is a tight crawlspace and not much room in there to work. This is in New England so some days it gets pretty cold.