ASK THE EXPERTS: SHW Pipe Insulation

Pipe insulation
Exterior solar hot water plumbing calls for high-temperature closed-cell pipe insulation. The insulation below is clad with a weatherproof aluminum-finish jacket.
Pipe insulation

We installed a DIY drainback SHW system with some recovered/rehabbed Grumman SHW collectors. The plumbing running to and from the roof-mounted collectors is 3/4-inch copper, which I’d like to insulate. In the past with another system, I’d tried using standard foam pipe insulation for household hot water piping, but this melted during the hottest days and did not hold up to UV light exposure.

Can you recommend an appropriate insulation for exterior SHW copper plumbing? Do I need to paint it with something to protect it from UV light? I’ve looked on all of the Home Power advertiser websites, but nobody lists insulation, besides what’s on the pre-insulated tubing packages.

Thanks for everything! I never would have pulled off this system without the confidence I got from reading Home Power over the years! Besides the inefficiency due to lack of insulation, the system is working great.

Matt Steiman • Dickinson College Farm

I’ve always used a product called Halstead pipe insulation from a local insulation company, but Halstead has been taken over by Rubatex and subsequently acquired by K-Flex, another good alternative.

Generically, you should search for high-temperature closed-cell pipe insulation if you are unable to find the above products at a reasonable cost. Expect to pay $1 to $3 per foot depending on the pipe diameter and insulation wall thickness.

Any insulation used outdoors will need to be weatherproofed. The minimum is aluminum tape, although some installers use elastomeric coatings, such as Snow Roof, or even ABS pipe over the insulation. Another option would be K-Flex Clad AL tube insulation with an aluminum-finish jacket. Expect to pay a good deal more for the covered variety, but you’ll only need it where the pipes are exposed to the elements.

Thanks for your comments on the Home Power content—it’s always appreciated.

Chuck MarkenHome Power solar heating editor

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