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Insulating baseboard hot water lines

SteamingatMohawk Member Posts: 1,004
I have owned houses since 1970, including baseboard hot water, heat pump hot air/AC and steam. With all the energy efficiency, etc. things going on, I haven't seen nor heard of any discussion on insulating the baseboard hot water lines to and from the baseboards. It seems to me with a starting temperature of 180F, there has to be some heat loss along the way inside the walls, etc. that would be better distributed to the baseboards.

Over the life of the insulation, my guess is that the cost of material and labor would be less than the savings.


  • pecmsg
    pecmsg Member Posts: 4,853
    That heat is lost to the interior.

    No if there in an outside wall then maybe.
  • neilc
    neilc Member Posts: 2,703
    any heat loss from an uninsulated heat pipe is still inside the building envelope,
    so unless that heat pipe runs outside, or in the garage, or vented crawlspace or attic, the heat loss is still heating the building,
    Now, if the heatloss is over heating say the basement,
    or if you're just not getting enough heat to the living space,
    then consider adding the insulation,
    known to beat dead horses
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,004
    While I agree the heat is at least initially still inside the building, I believe the fundamental principle is to put the heat where you want it, not just where it has to travel through on the way to those locations.

    The same goes for steam heat. While the situation is somewhat different, the same concept applies.

    See this: https://www.heatinghelp.com/systems-help-center/the-importance-of-insulation-in-steam-heating-systems/

    Admittedly Dan's point for the returns is different, but as I said above put the heat where you want it.

    Think about how many feet of copper is used to run all around a house (even more for a second story) giving off heat to spaces that don't need any more heat than they get from the rooms.

    Back in the 1970s the Northeast had many raised ranches built and the copper was run in the overhangs. One winter the house we owned in Windsor, CT had a prolonged power outage. When I got home from night shift work, I was able to open the zone valves and get the system running on natural circulation. That worked good enough to keep my system from freezing and rupturing the copper. When I got done with my house, I tried to help a neighbor, but it was too late to get their system going with no pumping power. Many of the houses had leaks. I just happened to be lucky, unlike my neighbors.

    As an exercise, make a guess at how many feet of copper are in a reasonable sized house, then estimate the heat loss from 170 to 70 for all those feet of copper. I used the average of 180 and 160 for supply and return temperatures. Here is a table of heat loss for pipe from Gerry Gill's web site.


    1 inch copper has about the same OD as 3/4 inch pipe. Ignoring the greater thermal conductivity of copper (only makes the case even more), a 100F temperature difference between the fluid and surroundings yields 59BTU/hr-ft. Multiple that by a round number like 100 feet of copper give 5,900BTU/hr of run time. For round numbers assume 6000BTU/hr and a 120,000BTU/hr heat source. That's about 5% wasted heat. Now take a stab at the cost of 1/2" of insulation and make an assumption it reduces the heat loss to half of the bare copper. Without stating the source (its not allowed on HH) 3 feet of 1/2 inch insulation is about $9 per piece, ignoring price reductions. So material cost would be $9 x 33.3 or $300 one time cost. If you saved half of that 5% over the life of the system, how long would it take to break even. I don't know the $$/(BTU/hr), but my unskilled guess is it would take maybe a few years, then after that it's all savings. Fitting in preformed insulation wherever possible has some labor cost, which would make the time to break even somewhat longer...I am not skilled enough to estimate that. Even if it took 10 years, it still seems worthwhile.

    So, then why hasn't it been done? My guess is when energy was cheap, it wasn't seriously considered. These days it may be a different story.

    I encourage HHers with real life experience to comment on whether my wild guess is credible or not and provide any real historical background as to why baseboard hot water wasn't insulated between the baseboards.

  • Jamie Hall
    Jamie Hall Member Posts: 23,313
    It is basically a cost/benefit problem, as you say. Cedric's home doesn't have hot water heat -- so it would be moot. Nor is there any insulation on the wet returns for the steam system -- might save a bit, I suppose. What there is, though, is insulation on all the domestic hot water lines where they are accessible -- which hasn't made a discernable difference, but feels good -- and on the cold water lines -- which has made a huge difference, since in the summer the cold water temperature is well below the basement dewpoint, and those puppies were proper waterfalls before they were insulated!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,151
    its rare to see a commercial building the doesn't have all the piping insulated , cold, heating, chilled, and duct work
    in some areas dhw lines are required to be insulated to meet energy codes, even in residential applications

    The heatloss from the  copper tube has a lot to do with the air temperature around it, flow  rate, diminishing temperature, etc.

    Certainly no harm in adding insulation. 
     It’s the same discussion with balancing valves. They are rare in residential but they do add efficiency to the system by delivering exactly what is required.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream