The piping to and from my boiler, which consists of 3/4 and 1-inch pex-al-pex lines through unheated building space, needed to be insulated. It worked OK without insulation, but it works a lot better with it. Part of this run goes through the barn ceiling joists, while the other part goes through a greenhouse, half of which is not being used at the moment, so it's pretty cold in there. My problem was that after switching to pex from copper this past summer (I used the copper to make my heat exchanger), I was afraid that mice would nest in the insulation and chew through my nice new pex. Obviously, it's warm around the piping, so it would be only natural for the mice to seek refuge in there. Since I can't beat 'em, I figured I'd have to protect my pipe runs. What a pain! Here's what I came up with. It's pex with foam pipe insulation, wrapped in fiberglass bat insulation and jacketed in heavy wire screen. Then, in the case of the greenhouse run, covered in another layer of fiberglass and wrapped in plastic to keep everything calm and dry. They may get into there, but they won't get at my precious pipes. The last pic is the run through the barn ceiling. A little different approach, but it gets the same job done. I put fiberglass and plastic over the top. I'm building a cabinet to house the greenhouse run, but I'm such an abysmal carpenter that I'm not posting any pics of that until it's done. And maybe not even then. Whatever. It does have a much higher WAF than bare pex snaking across the floor.