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Thread: Pex and Condensation - to insulate or not to insulate?

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    DIY Member techinstructor's Avatar
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    Default Pex and Condensation - to insulate or not to insulate?

    We're putting Pex in our new home. I've never had Pex in a house before (only PVC) so I'm not sure what to expect. Most of the Pex will be under the floor in our basement. The full basement has poured concrete walls (10") that are insulated on the outside (2" Styrofoam) so freezing is not an issue. However, we are are concerned about condensation because of the hot, humid summers we have here in NC. The basement will stay pretty cool even with no air conditioning and the basement is water-tight (Bituthene on the outside, Dry-Lock on the inside) with both interior and exterior drain lines. But the humidity in July and August is continually high. We're concerned that the cool well water in the pipes will cause condensation on the exterior. At our old home, also in NC, we had PVC pipes in a not-so-dry basement; they cold water supply lines dripped in the summer time from condensation.

    I'd like to get some feedback from those of you who are more familiar with Pex as to its propensity for condensation on its surface.

    Thanks

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    In the Trades Tom Sawyer's Avatar
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    Try it. If it sweats, insulate it then.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    Moderator & Master Plumber hj's Avatar
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    You probably had CPVC at the former residence. If you had had PVC, condensation would have been the LEAST of your problems. ANY TIME a surface's temperature is lower than the dew point of the moisture in the air it WILL condense, whether it is a pipe or a plant leaf, (think dew in the morning). PEX has a lower rate of thermal transfer, but it WILL eventually reach the temperature of the water, and if that is cool enough to induce condensation, it WILL happen.
    Licensed residential and commercial plumber

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    DIY Member techinstructor's Avatar
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    Quote Originally Posted by hj View Post
    You probably had CPVC at the former residence. If you had had PVC, condensation would have been the LEAST of your problems.
    No, it was PVC for the cold supply and CPVC for the hot. My husband put it in about 10 years ago because the original iron pipes were badly corroded. We had no problems from either the PVC or CPVC and had no leaks; we didn't know about Pex at the time. We've read since that the glues in PVC don't last, so I guess we're getting out at a good time. That basement had water leaks from underground water sources that were a much bigger problem than the drips from the pipes.

    Quote Originally Posted by hj View Post
    ANY TIME a surface's temperature is lower than the dew point of the moisture in the air it WILL condense, whether it is a pipe or a plant leaf, (think dew in the morning). PEX has a lower rate of thermal transfer, but it WILL eventually reach the temperature of the water, and if that is cool enough to induce condensation, it WILL happen.
    Thanks HJ, this is what I suspected. I'm also thinking that the hot supply will benefit from insulation as well.


    Any suggestions as to good pipe insulation? I read a good thread here about how to insulate with Armaflex by Armacell. It's sounds like premium, top-of-the-line stuff, but I'm afraid it's going to be expensive. Are there any other good brands to seek out?

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    Moderator & Master Plumber hj's Avatar
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    Your options will be limited because you want the "split" insulation with the contact cement which seals the insulation when it is pressed closed. PVC is NEVER "permitted" INSIDE a building on EITHER hot or cold. You WERE lucky.
    Licensed residential and commercial plumber

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