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Most Efficient Radiator Heat-- Constant Temp or Turn Down?

I normally turn down my radiator to 54 ir 55 at night and keep it at 64 or 65 from 6-11pm while I'm home. My neighbor told me that with hot water radiators it's more efficient to keep them at a constant temperature instead of turning it down at night but I can't find any information on it anywhere.

Anyone have an idea on what would be the most efficient;/cost effective method?


  • icesailor
    icesailor Member Posts: 7,265

    I don't know what "current" studies show but in practice with me, there is no greater savings than set back thermostats. Ones that change at pre-set temperatures. I find that you will become used to lower temperetures and you don't forget to turn them down. I have used them for myself and my customers. I have accurate records of fuel savings for years. I have never have a customer complain and say that they didn't save them money.

    My FLA condo has one. The AC runs off it. I never need to worry about it being off when I get home.

    Outdoor reset will seriously conflict with them though.

    Do what you want. They have worked very well for me over years of use.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Turn down...

    I would complain, though. Because my house has radiant tube in an on-grade slab. The time-constant of that slab is about 4 hours and if I change the thermostat setting, it can take about 12 hours to satisfy the new setting. And the "smart recovery" cannot deal with such large lags.

    And, as you pointed out, outdoor reset, that I have, does not make things any better as far as turn-down is concerned.

    I know turn-down helps with forced hot air systems. It works with usual hot water baseboard systems (the ones with about 180F water in them). I have a zone with baseboard in it, but it typically has 120F water in it, so a setback of about 2 degrees is the most I can manage. I do not know, but I imagine they are not as effective with steam, depending on the thermal mass of the radiators.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013

    the higher the mass of your emitter/home, and the lower your heat load, the less setback can do to help you.

    the higher your heat load, the more useful setback is.

    I would say in any house where it is useful, an energy retrofit should be planned. Sure sign of a higher than necessary heat load.

    the test for an existing home is easy. If you turn down a thermostat 10 degrees AND GET ANYWHERE NEAR THAT overnight, and can recover from it an hour or two, you should be using setback. that's an unscientific test of course but the upshot is if you don't lose much temp overnight or if it takes a long time to recover setback is a waste of time.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    the test for an existing home is easy.

    I like the way you look at things here.

    "the upshot is if you don't lose much temp overnight" ...

    I sure don't. Back with my old boiler, which quit almost every year from dirt in nozzel, failed h.v. transformer, etc., I never called for emergency service, even on weekends. If it quit on a Friday night, I waited until first thing Monday morning. By then, I needed a sweater, but that was it. It would drop from 70F to 58F or 60F, which was no fun, but not worth paying extra for emergency service. I did do creative things with the window shades, and stuff,, and have lots of insulation and Marvin windows too.  And when it was fixed, it would take a 24 hour day to recover from a setback like that, at which time the slab would be so hot the next day as to tempt the double-hung solution.

    I have had the new boiler for only 18 months, so it has not failed. But realizing how badly the system works with setbacks, even if they saved me fuel I would not use them.
  • Gordy
    Gordy Member Posts: 9,514
    Skip the Set Back

     Rob makes some very good points I think.  I would add unless your going on vacation or maybe gone for the week end skip it.

    Remember is lack of comfort really worth the minimal savings. A BTU is a BTU. If you let the structure, and its mass cool down it will take as much energy to heat it back up. Plus you are not comfortable in the process.

    But thats just me.

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    From my perspective...

    If you turn the thermostat down 10 degrees F and it falls that much overnight, you need to find the heat leaks in your house and FIX them.

    And if the boiler is capable of recovering the house in short order, that is an indication of a grossly oversized appliance that is most probably short cycling, even at design condition, that could/should be replaced with a properly sized or modulating appliance.

    But that is just my take on things.

    I agree with Gordy. Conservation at the expense of human comfort is expensive...

    Putting individual radiators on their own non electric thermostat, adding outdoor reset and then setting those individual radiators to use patterns will save energy and keep people comfy when and where they need it.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • I agree Mark!

    I`m sure you hit the "nail on the head",, setback helps, but what you need, is what you need!
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    I'm with you mark

    good setback savings is the hallmark of poor construction/energy decisions.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
This discussion has been closed.