Insulating Chilled/Cold Water Lines

Good day folks,

I am wondering what best practice is for insulating chilled and cold water pipes inside a dwelling regards to protecting from condensation.

I will have both domestic cold and chilled space conditioning PEX circuits throughout the home. 

I plan on using Armaflex continuous coil elastomeric rubber insulation (1/2" thickness) for the runs between fittings.  

But what do you do at framing penetrations.  Obviously I cannot drill out a 1-3/4" hole in 2x4 plates and studs, so what is best practice to seal at these points to prevent condensation??  Specifically worried about double plates or multi-ply studs.

Also, what is best practice around manifolds, valves, etc.?   I have some Armaflex flat stock.  Should I just make an air tight box around the device leaving things like valve handles accessible?  

Any advise would be greatly appreciated.

(PS I know not to insulator circulator motors, zone actuators, end the like)

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  • After having seen several problems like this - here is my recommendation. You can try what ever you think is appropriate.

    Use the Armaflex (or similar) everywhere you can. Make sure you air/vapor seal all seams and joints. I would use a mastic and scrim (open fiberglass mesh reinforcement) to seal the seams and joints - adhesive tape is NOT adequate.

    At single studs, drill the hole at least 1/4" larger than the bare tube. Use shims to keep the PEX centered in the hole. Fill the annulus with foam caulk (Great Stuff, etc). I would make sure the outside diameter of the foam outside the stud is the same as the outside diameter of the Armaflex. For multiple studs, make a sheet metal sleeve that spans thru ALL of the studs. You probably need to drill multiple studs 1/2" larger than the PEX and very carefully shim to maintain at least a 1/4" of foam on each side. (You might want to check my seat of the pants foam R-value calculation on that to make sure it stays above dew point between the studs.)

    In some climates - condensation in building cavities is not a problem because it is very rare. In some climates (like mine), it is guaranteed 24 hours a day for 6 to 8 months. That will rot you building structure. If your air conditioner is the means of humidity control, the PEX will sweat. The cooling water MUST be below the indoor dew point of the AC cannot control the indoor humidity. Most buildings in humid climates will have a dew point temperature inside building cavities that is some where between the indoor dew point and the outdoor dew point.

  • Just a follow up to Mark's post "cold waterlines in this space wont be exposed to outside humidity"

    I am actually more worried about the indoor summer time humidity.  Typical indoor conditions will be somewhere in the 50% -60% indoor humidity at 76ºF (cooling room setpoint).  Dewpoint at 50% would be 56ºF. The tubes will be carrying ground water at around 45-55ºF depending on time of season, so condensation is all but guaranteed if the pipes were not insulated and air sealed.

  • Thanks for reply Mark - appreciate the follow up.

    Most of the piping will be routed through interior walls, so the VB would not be present.

    I am generally running continuous PEX lines from manifold to fixture stops, so will not have hidden joints.  The manifolds will all have ceiling or wall access panels and yes I have extensive records including video, photos, and AutoCAD drawings showing the routing of all services.  Good advise.

    Not sure about the pool noodles - they work out to between $0.10-$0.17 per inch and the Armaflex in 100ft coils is only $.08 per inch and much easier to work with. (amazon)

    Armaflex IPAPC05812 1/2" x 1/2" x 95' Continuous Coil Pipe Insulation, Rubber: Tools & H…
    Armaflex IPAPC05812 1/2" x 1/2" x 95' Continuous Coil Pipe Insulation, Rubber: Tools & Home Improvement
    • @Sean, by closed cell foam noddles, I think Mark is referring to the Armaflex or similar. I'm guessing he missed in your original post that that's what you're planning to use.

      • :-) - Guess I should not read so literal! That makes more sense.

  • Expanding spray foam in a can and also the closed cell foam "noodles" are options I didn't see mentioned.

    If your floor joist s are properly insulated & sealed off with a vapor barrier, cold waterlines in this space wont be exposed to outside humidity greatly diminishing /preventing condensation.

    Mark or label where all connection /splits/valves are with a bright color, plus make a sketch or diagram where these connections are ; I actually marked these connection/splits/valve on the rigid foam moisture barrier insulation panels at the respective locations once installed with removal screws for easy access.

  • Hi David,  Thanks for follow up.

    It is becoming common to insulate the cold lines to prevent condensation now that most new construction turns basements into living space.  We have a LOT of dew cycles in our climate (probably thousands a year), so pipe sweating has always been a problem.

    What do people think of this product. Would the Velcro be air tight enough to prevent condensation?

    • Realized the comment above did not make total sense.  Of course our outside dew cycles has nothing to do with interior pipe insulation.  But yes we do have pipe condensation issues.  Cold water lines (incoming temp 40F-50F) are below the dewpoint of interior air for much of the year.  I would have to get the humidity down to below 36% in the summer to prevent condensation.  Not going to happen.

  • The wood itself provides some resistance (about R-1.25 per inch for a typical stud) so you just need to butt and seal the insulation tubes to the stud face. Injecting foam into the seam seems like overkill. I would just overdrill the penetration slightly and squirt some calk or single-part foam into the annular gap before abutting the insulation tubes.

    You probably already realize that you don't need to insulate the radiator zone loops since the supply water can never be allowed to drop below the dew point.

    Re: Manifolds, valves, volutes and other components -- sometimes it's easier to use tubes, sometimes it's easier to use flat stock. You'll figure it out as you go.  Either way, it's easy to get the foam to conform to whatever shape you're dealing with.

    Re: domestic cold water lines - Your house should be significantly drier than your neighbors, no? Is it common practice to insulate domestic cold water pipes where you live?

  • Thanks Sean - I do not have 'wet walls' most places I will be installing the supply tubes.  So definitely cannot drill holes larger enough to allow continuous insulation in the 2x4 sticks. And even a 2x6 would not be allowed by code to drill a 1.75" hole.  And on a optimized floor plan, 2x8 or dbl-stud walls would take up far too much room.   

    I do not have many through-framing routes, most is going through my open web floor trusses.  Guess I will just try to seal insulation to each side of framing as best as able.  May also try to drill through seam of multi-ply down to pipe penetration with say a 3/8" hole and inject sealant to create air barrier at that location.

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