Insulating water lines in attic?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by nofears67, Nov 2, 2010.

  1. nofears67

    nofears67 New Member

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    I'm building a single story home in Oak Glen, Ca. The plumbing for the home runs above the ceiling. My hot/cold trunk lines are both 1.25". The hot line is already insulated along with the recirculation loop.

    I am thinking about insulating the cold lines myself to cut down on the noise that is heard when water is running.

    Are there any issues I should be aware of regarding insulating cold water lines that are in an unconditioned attic space?

    My roof has radiant barrier sheeting and the ceiling insulation will be R-38, but there are a number of roof vents and we experience freezing temperatures once and a while throughout winter.

    Thanks for any input!
    Last edited by a moderator: Dec 26, 2010
  2. jimbo

    jimbo Plumber

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    Ideally, the water pipes would be under the ceiling insulation, so they are mainly exposed to the house temp at the ceiling, more than the cold attic temp.

    [​IMG]
    Last edited by a moderator: Nov 2, 2010
  3. nofears67

    nofears67 New Member

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    Some of the R-38 attic insulation may make contact with some portions of the pipe but it certainly will not "encapsulate" them.

    Should I be concerned about condensation on the cold lines if I was to insulate them in the attic space?
  4. Terry

    Terry Administrator Staff Member

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    You are better off to leave the pipes bare, and lay insulation over them like a blanket.

    [​IMG]
  5. nofears67

    nofears67 New Member

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    Sound control is the primary objective here...
  6. Terry

    Terry Administrator Staff Member

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    That may be the case, but when pipe in an attic is insulated from the warmth of the home, you will have a lot more to worry about then sound.
    Have you ever seen a split copper pipe in a ceiling? I've seen entire ceilings drop onto the carpet below.

    However, since you are in Riverside California, when does it ever freeze anyway?

    For sound, it's the attachments to solid objects where most of the sound comes from. Work on the attachment points, and it should help.
    Last edited: Nov 2, 2010
  7. Thatguy

    Thatguy Homeowner

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    So you need some viscous pipe wrap material to damp out the sound but that also conducts heat, and then use the diagrammed layout to allow house heat to warm the pipe.
    Rubber is viscous but has 2000x the thermal resistance of copper. Depending on the heat capacity of the water filled pipe, incoming water temp. and the amount of time that the air is below freezing, it might work.

    This link is one step in the calculation
    http://www.engineeringtoolbox.com/copper-pipe-heat-loss-d_19.html

    Or, maybe someone makes "shock mounts" for pipes. This would prevent the pipe noise from being transmitted to the house frame.

    Your outside design temp. is right at the borderline, pg. 74 of the link.
    http://host31.spidergraphics.com/nra/doc/Fair Use Web PDFs/NRAES-137_Web.pdf

    You could also use a t'stat controlled heat tape to warm the insulated pipe but then
    it's a lump sum up front plus a continuing very small cost for elec.
    vs.
    a lump sum up front for the non-elec. solution but the outcome is more iffy.
    Last edited: Nov 2, 2010
  8. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Freeze protection for pipes in attic

    My under-slab copper pipes failed a few years ago, so I re-plumbed the house overhead with CPVC. There are 2 80' 3/4" manifolds with 1/2" branch lines for each fixture along the way. Thanks to global warming, "deep freezes" are becoming common here in central FL, and I'm wondering how best to prevent these pipes from freezing. I'd love to know exactly how long it would take for CPVC to suffer damage at low temperatures, but so far the Flowguard folks have not responded to my requests for information.

    So far, the "dribble water from all the fixtures" method has worked, but the new showers, toilets and washing machine don't dribble, and there are portions of the sytem that dribbling won't help anyway. In a really severe freeze situation, I can drain everything, but that gets old.

    I've looked at several "heat tape" - style solutions, but none were designed with a multi-branched system in mind. The most elegant seems to be the Easy Heat "Freeze Free" cable, which is self-regulating. In theory, it you could cut and splice the bulk cable into any topography you want as long as no leg exceeds 75' from the power source, but the Easy Heat folks insist on strictly linear application of the cable using only their proprietary fittings. It's also wicked expensive, but I'm leaning toward this in spite of the manufacturer's warnings.

    There are other pre-formed cable/thermostat systems that could be forced into conforming to my layout, but by the time you buy lots of short cables, the price is really outrageous. Operating costs for all these heat-tape approaches are reasonable, since power consumption runs only 2 or 3 watts per foot.

    Another alternative is simply to heat the attic to maintain a temperature above 32°. I can get a used AC airhandler unit with, say, a 5KW heat strip, and just fire it up when necessary, using the branch circuit for the existing home airhandler. Or, I could divert the airflow from the existing airhandler to heat the attic instead of the living space. The price is right, but the operating cost is obviously higher than the heat-tape method. I already block the attic vents to restrict outside airflow through the attic, but the roof and attic aren't tight or insulated at all. There's a good argument for insulating the attic to some degree, since that would also be beneficial in the summer cooling season.

    The last idea so far is to arrange a continuous circulation through the entire system, via the water heater, to maintain water temperature above 32°. This is pretty-much a nonstarter.

    Interestingly, I brought this problem on myself by adding insulation to the attic -- prior to that, there was enough heat transfer from the living space to keep the attic at a safe temperature, but no more.
  9. Redwood

    Redwood Master Plumber

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    Its a pity that the Florida plumbers don't feel the need to plumb like they do a little further north.
    The pipes would be run against the sheetrock ceiling with insulation on top and would probably work well for you providing freeze protection as well as cooler water in the summer.

    They didn't run lines up the outside of the house did they?

    I'm also not a fan of CPVC at all. If that stuff freezes its all over!
  10. hj

    hj Moderator & Master Plumber Staff Member

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    I have NEVER heard of using CPVC with a manifold. It sounds like it must have used an enormous amount of pipe and fittings. The only two ways to prevent freezing are to either apply heat to the pipes, OR keep the cold away by heating the area. We cannot tell you which is most expedient, and economical for you since we would have to see the situation first. Disregarding the heat tape manufacturer's instructions COULD create a hazardous condition, unless you treat EACH branch line as an individual section. Circulating hot water using a "retrofit circulator and its bypass valves" would keep the hot line above freezing, and would probably also help the cold, at least to the water heater, since it would keep the water moving, thus keeping it above ambient temperature. The problem with a manifold system, however, it that you would need "bypass" valves at EVERY faucet, or at least the ones that could freeze, unless you modify the piping.
  11. Redwood

    Redwood Master Plumber

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  12. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    "Manifold" was probably a strong word to describe my situation. The hot and cold "manifolds" are just 80-foot long 3/4" pipes running the length of the house, with 1/2" branch lines going to each fixture or group along the way. Both hot and cold manifolds are center-fed above the water heater. Most branch lines go straight down from the manifolds, through interior walls, to the fixtures, but there are a couple that run about 10' before they dive down into the walls.

    The manifolds couldn't be run against the ceiling sheetrock for a couple of reasons: 1) the joists get in the way every 24", and 2) the pipes wouldn't have any protection from errant nailguns. They're about 12" above the tops of the joists. I did consider just blowing a whole heap of insulation over them, and may yet do that. The branch lines do run parallel with the joists, of course, and could be dropped down closer to the ceiling.

    CPVC is just about all they use around here, even in high-end homes. So far, everybody seems to like it, and freezing is not normally an issue. During the deep freeze of a couple of weeks ago, my attic got down to about 28° for a few hours, but my "canary" bucket of water I keep up there never froze over. I'm going to make up some 2' lengths of CPVC and fill them with water to hang up there (over the bucket) to see what happens. I have another canary bucket outside. On that cold day, when I went out at 5AM to pick up the paper, it was liquid. I walked to the end of the driveway, got the paper, and when I came back in there was about 1/8" of ice on it. When that last BTU leaves and triggers the state change, it happens quickly.
  13. Basement_Lurker

    Basement_Lurker One who lurks

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    That's a cool pic redwood.


    Mikey, you have a standard trunk and branch system, and both of those reasons for piping in the attic space only point to laziness and inexperience. Pipe penetrations in lumber are protected now by nail plates. If the insulation had been placed above the piping, you wouldn't have this problem. However, since the insulation is below it, if you now insulate above the piping, you won't be solving the actual problem. Insulation doesn't stop pipe freezing, it only slows it down. If the flash cold storms are very brief, then sandwiching the piping in insulation might be enough to stave off freezing. And I don't think leaving an unmonitored heating device (not including heat tape) in an attic is the safest choice.
  14. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Guilty as charged, as least as far as the "inexperience" part, and you can add "panic" to that -- the overhead installation was done hurriedly, since the house was without water. As far as nail plates, an earier post implied that the pipes should be laid directly on the ceiling sheetrock, so they'd have to be mighty big nail plates.

    Seeing the cross-section drawings that jimbo and Terry posted makes me think I can come up with something like that, and move the existing system on top of the joists to allow insulating like that. The pipes were placed as they were to get them out of the way of existing AC ductwork, but it might be possible to move them to run in contact with the ductwork, and then wind up placing both the pipes and the ductwork inside the newly-insulated space, killing a couple of birds with a few rolls of fiberglass.

    Aside, I've been looking at heat transfer calculations for pipe. I'm still fussing with details, but I'm encouraged to find that the thermal conductivity of CPVC is on the order of 2,500 times poorer than that of copper, so the time-to-freeze should be significantly longer for CPVC than for copper.
    Last edited: Dec 26, 2010
  15. Terry

    Terry Administrator Staff Member

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    When power is lost, ducts conduct cold very well.
    I would keep the pipes away from the ducts. It sounds like a good idea when the heat is on, but pipes normally freeze when the power is out.
  16. SRQGator

    SRQGator New Member

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    Location:
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    Glad I found this thread. Thanks to everyone for the great info.

    I'm about to undertake the same project as Mikey—slab house in Southwest Florida; failing copper; running new cpvc supply through the attic. I plan to follow the diagram provided above with the pipes atop the joists, creating an air pocket with insulation above and on both sides. Can I assume this would also prevent condensation during the hot, humid summer? Our cold supply down here is not very cold. Also, I'll be running the hot and cold trunk on the same path—how far apart should I run the parallel lines?

    Any other guidance would be greatly appreciated!
  17. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    All I can say about condensation is that I've never seen any on my pipes in the attic, which gets up to 120° or more in the summer. I've never measured the humidity in the attic, but as you point out the incoming cold water is probably around 70-90°, and the insulating properties of the CPVC probably help prevent any condensation. I had also never seen any condensation on the airhandler, until I insulated that with 6" of fiberglass batting all around -- looks like a pink igloo. Now if you slip your hand under the insulation, you can feel moisture (in the summer, not now -- attic was 34° this morning). Honestly, if I had it all to do over again, I'd probably go under-slab with CPVC or PEX, or PEX in the attic (mostly for ease of installation). One very handy feature of the attic trunk-and-branch layout is that each branch has its own accessible shutoff, which I wouldn't want to give up.
  18. SRQGator

    SRQGator New Member

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    Location:
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    Thanks. That's what I was hoping to hear about the condensation.

    You mention going under slab if you had it to do over. Is that mostly due to the pain of crawling around in the attic? I had not even considered that as an option, assuming the cost would be outrageous. If there are other significant factors I'd like to hear them. Otherwise, I'm inclined to suffer through the attic.

    Last night was a cold one for sure.
  19. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Attic-crawling pain is right up there, but the main reasons are freedom from worry -- about damage from leaks and freezing, and keeping the cold water cool (at least). Both of those fears can be mitigated by proper planning, materials, and workmanship. The under-slab replacement cost IS outrageous -- I was quoted over $4000 vs $1500 for overhead -- but the main deterrent is the mess. The plumbing cost was a small part of the overall job. And if you've got tile floors, with no spare tile for repairs, it's almost prohibitve. If your under-slab pipes are generally falling apart, then overhead is really the only option. But, if you've got a point leak (easily found by the Sleuth guys), I think it would pay to dig it up and have a look, if it's in an accessible area. If it looks like local damage or a failed solder joint rather than general deterioration, my advice would be to repair it and move on. I should have at least done that, but was discouraged by the generally shoddy workmanship seen on the plumbing that was exposed -- big globs of solder and lots of copper corrosion around the joints. God knows what it looks like under the slab, exposed to moisture and the corrosive soil. And, some overhead copper and abandoned underslab pipes I found suggested prior leaks had occured.

    Another option, which was recommended to me by an architect friend when we started this 6-month remodel job 7 years ago, was to start with a bulldozer. In retrospect, I think he was right.

    Attic got down to 34.7° last night, with frost and frozen buckets outside. Tonight is supposed to be bad as well.
  20. SRQGator

    SRQGator New Member

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    Location:
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    LOL, I hear that! I'm seeing the same thing you described with the original ines. Thanks again for the feedback.
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