Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Insulating beneath buffers and indirect tanks?

dave123
dave123 Member Posts: 55
I think a lot of jurisdictions now have requirements to insulate beneath electric water heaters, using some variant of rigid foam. Makes me wonder about the usefulness of doing the same beneath buffer tanks and indirects, at least those that sit on a concrete base, which is probably the majority. Aim is to lessen heat lost through both radiation and conduction into the floor.

Also, I've "heard" that the R values given to tanks by the mfr only needs to apply to the sides, not the top or bottom, but don't know if that is true, Has anyone here ever seen one cut up?

If the bottoms aren't well insulated, then a lot of heat could be lost to the floor, at a steady pace. Curious what others think about this. Should buffers and indirects get the same sort of insulation under them as electric water heaters?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,111
    One can argue this one two ways. First, of course, is the obvious one which you are addressing: if one considers the tank in isolation, then obviously any insulation is good, and more is better (there is a point of diminishing returns, of course). However, for most people the tank is not isolated, and any heat loss from the tank goes into the space and is useful to heat that space, assuming that it is a conditioned space or at least next to one -- which, in most cases, is true.

    Of all places, then the bottom is the one which should have the most insulation -- assuming that the bottom is in direct contact with a basement slab. However, there is a good deal to be said for ensuring that the bottom is not in contact with a basement floor, for reasons other than insulation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steve Minnich
    Steve Minnich Member Posts: 2,675
    It's been a while since I've cut one open, but I'm fairly certain both buffer tanks and indirects are well insulated on the bottom.
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
    STEVEusaPAethicalpaulRich_49
  • hot_rod
    hot_rod Member Posts: 15,042
    I think insulation below would be wise. Hot goes to cold, that slab will pull some energy from a warm tank. 180 tank 55 slab is a big delta.
    I think most all tanks are insulated with expanding foam nowadays. Gas fired tanks may have some fiberglass around the opening.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Steve Minnich
    Steve Minnich Member Posts: 2,675
    Hopefully, there are fewer and fewer systems being designed for 180 degree water. 
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
  • JUGHNE
    JUGHNE Member Posts: 8,961
    My DHW storage is a 120 gallon Rheem "air head" solar tank.
    It uses a tube in shell HXC (home made from the scrap pile).
    Came with fiberglass insulation. I try to put everything up on 4" concrete blocks anyway. For this a 1" thick blue board was put down first and then trimmed around.
    Old FG insulated tanks had no insulation on the bottom as the weight would have crushed it to nothing.

    Been in service since 1995......pretty good tank and even better water.
    I have considered putting more insulation wrap on the shell, but keep thinking as soon as that would be done it would start leaking. :/
  • Another place sorely lacking any insulation at all is the bottom of cast iron power burner boilers. 200 F water and a cold slab with very good radiant heat transfer characteristics. For the stage fired new little baby 80 steam boilers we just put in at my church, I put a 1/2inch thick duct liner blanket under there to at least keep most of the heat from going directly into the slab. I really should try to find some way to keep the heat from leaking out into the room from the space into the room
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,290
    Hi, This from an older study done by Bonneville Power Administration... Under-tank board insulation can achieve 53kWh annual savings, and R ll external wrap can save 168 to 502 kWh per year for energy-efficient and conventional water heaters respectively. B)

    https://inspectapedia.com/plumbing/Water-Heater-Standby-Loss-Elk.pdf

    Yours, Larry
  • Jamie Hall
    Jamie Hall Member Posts: 17,111
    Just keep in mind what I noted above: heat which is "lost" into a conditioned space is not lost. One must think in terms of the whole system, not each constituent part by itself.

    Off topic example: one of the reasons the late 17th century houses in New England were quite comfortable (and still can be, if not messed with) in the winter is that huge central chimney with the walk in fireplace. I can hear it now: but all that heat is wasted up the chimney! Weeping and gnashing of teeth. Nope. That "wasted" heat heats the chimney, which in turn heats the rooms both on the ground floor around it -- and on the upper floors.

    But. You do need something under there on a water tank to keep it from the damp floor.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England