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I live in Houston, and I'm trying to re-insulate my external pipes, which are a mix of PVC pipes and fittings and brass valves. Most of my fellow Houstonians use foam polyethylene insulation and duct tape the seams only (which is how I found the pipes on my house), but in my research I've seen many comments that foam polyethylene is not suitable for outdoor applications. That makes sense to me, because it always ends up dry, crumbly, and disintegrating when I come across it, and I'm guessing that makes it less effective as insulation (but please correct me if it's still doing a good job). Those people recommend nitrile / rubber insulation instead, e.g. Armaflex.

When I watch Frost King's video titled "How to pick the right pipe insulation", they only use rubber insulation outdoors on an AC's copper refrigerant line. Well, that's what every AC in Houston uses too. I know the manufacturers say you can use rubber insulation on PVC pipes, but is it actually more effective than foam polyethylene?

But maybe rubber insulation isn't enough. I've seen comments saying you also have to paint it (not tape it) to make it UV resistant. Armaflex sells a product called Armaflex Shield that comes with a UV resistant coating already, but I can't find it on the shelves. Do I have to paint the "basic" rubber insulation? Is a UV resistant 10 mil pipe wrap tape good enough? Do I really have to cover the entire length of insulation?

Lastly, gaps. The jobs I see in the wild in Houston leave gaps everywhere, but often comments say we should cover everything right up to the edge of the valve handle, with perfectly mitered elbows and no gaps anywhere, and that rubber insulation must be joined with glue.

I've seen dozens of videos demonstrating "bad practices" according to comments, and not a single video demonstrating installing rubber insulation, glued and painted, on outdoor PVC pipes. Is this "best practice" just a myth?

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  • Best practice looking towards "the next freeze event" (and there will be one) is to bury them adequately or move them inside the building envelope.
    – Ecnerwal
    Commented Mar 21, 2021 at 16:14
  • That's not helpful, nor does it answer my question. In a freeze where we lose power for 36 hours, that won't prevent a burst, and in a freeze where we don't lose power, or that lasts only one night, insulation is enough to protect the pipes.
    – John Freeman
    Commented Mar 22, 2021 at 17:46

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Nothing will prevent freezing if water is not moving. If not moving water you must drain pipe to prevent freeze.

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  • To elaborate, with no heat source to the water inside the pipe it will freeze with your long power outage. It has to be drained or kept running (so the water in the pipe is refreshed with ground-temp water). The insulation in this case only gives you a bit more time before freezing.
    – blarg
    Commented May 28 at 19:50

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