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Will shutting off steam radiators save $$$?

Angela_2 Member Posts: 67

I have an oil-fired 1911 steam boiler. My boyfriend and I are having a disagreement. If we shut off the third floor radiators (or any other radiators in rooms we aren't using), will this save any oil by radiating less heat? The house is all on one zone, controlled by a thermostat on the 1st floor.

(And yes, I know the boiler should be replaced and about all the other things I can do to save $$$, but I'm wondering specifically about this question...)

Thanks, Angela


  • Brad White
    Brad White Member Posts: 2,398
    Generally Speaking

    yes it will. By reducing the amount of surface area the steam needs to serve, it maintains pressure that much longer. The difference may not be perceptible or if so, by much.

    (All steam boilers want to do is to maintain pressure when called upon to provide heat. Sort of how guys, when asked to be supportive to meet your emotional needs go down to the basement or something ;).

    Another less desirable effect it can have is to cause the boiler to short-cycle, especially if it is over-sized already. Say you have 450 SF connected to a 600 SF boiler- you shut off 50 SF and you are that much more over-sized, hence will cycle more than it did. This decreases efficiency but I would say not so much that it cancels out what you are saving by not heating.

    Yet another possible side-effect is that the radiator you choose to close could also be assisting in venting the mains and radiators nearby, or at least contributing. Ideally the mains should be well vented, but if the radiators are serving this function by default, you may find yourself with slower heating elsewhere. Will this loss of efficiency cancel out the savings of not heating a room or two? I really do not know, but doubt it.

    The inefficiencies are cumulative and I cannot say where the tipping point is.

    A better solution though is to place thermostatic radiator vent valves (Macon OSPK is one model, Danfoss is another). This will allow your radiators to use what they need based on temperature. Suppose you forget to open that valve and freeze something if the room is isolated, for example?

    If you DO close the valves, please do so when the boiler is off. If the radiator is full of steam, the water has to get out. Those hand-valves are made to be fully open OR fully closed. No where in-between.

    That you have an eye toward improving the system as a whole later (beyond your question here) is a wonderful thing.

    So, who's side did I come down on? :)
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Fred Harwood_2
    Fred Harwood_2 Member Posts: 195
    Saving fuel

    Don't close single-pipe radiator valves. Instead, replace the air vents with adjustable vents, and set them by observing over several cycles to the temperatures you want in each room. That lets you save on steam while guarding against freezing anything on very cold nights.
  • Plumb Bob
    Plumb Bob Member Posts: 97

    It's not like if you have ten radiators and switch off one, you save 10% of your bill. That's not how it works.

    Even if a radiator is shut off, rooms are not insulated from each other, so heat leaks into that room from other rooms. The room with the shut-off radiator may be a few degrees colder, but it is still being heated (it isn't anywhere near as cold as the outdoors).

    You can certainly try turning off a radiator, but the effect is very tiny and you will probably not notice any difference in the bill.
  • Angela_2
    Angela_2 Member Posts: 67
    Thanks all (for answering yesterday's question)

    Thanks you guys. You are all so dependably there each year when I start the heating system with a whole new set of questions! (You see, mostly I just THINK about getting rid of the old boiler, I'm really quite attached to and impressed by it, what could I possibly replace it with that would work so well for 90 years?) Too bad it's such a guzzler. I bet it could run another 50 years at least.

    To answer your question Brad, you came out kind of in the middle because you agreed that money would be saved, but don't really think it's going to be a lot (I gather). Walter thinks we'll save $1000 (on a $3500/season bill). I've maintained the savings would be negligible, and that shutting off the radiators could cause system imbalances or other problems. I am especially concerned because there is a bathroom up there (though I know that heat rises and these pipes probably won't freeze anyway because they aren't on the outside wall and the chimney where a hell of a lot of my heat goes IS in the wall right next to where those pipes run.)

    I should also mention that when we have this argument, I tell him to read The Lost Art of Steam Heating first and then lets fight. I've read it; he hasn't. He is probably better able to understand the concepts as he is already very mechanically inclined, but I have the greater motivation because this has been my house for 7 years now and I'm an old house girl (so I love my steam heat). The truth is, a year later, I need to read the damn thing again myself, though I'm sure that this time, I WILL REALLY REALLY GET IT and maybe even fully retain it for midsummer arguments months later.

    Also, Walter's suggestion was not just to shut the radiators off, but also to plastic off the stairwell (I didn't understand this when I posted)) and the whole floor to help keep the heat back down on the first two floors. I hate this idea because I at least want to be able to check the bathroom on really cold days/nights. He says we can cut a slit in the plastic etc. if I have to go up there. Someone agreed with him that this combined with shutting off the radiators would save a ton of money.

    I just don't think it's going to be a lot of savings, and trying to hang this plastic and get it to keep hanging is a lot easier said than done. I also agree with you all that rather than shutting the valves I put adjustable vents on and set them at their lowest setting.

    Thanks again, Angela

  • David Nadle
    David Nadle Member Posts: 624
    Give TRVs a look.

    Someone else mentioned TRVs, It's a good way to go. I put thermostatic vents on two bedroom radiators that are probably oversized. They don't cost that much and they work great. Easy to install on one pipe systems.

    The Danfoss RA2000 TRVs have a "50 degree" setting to prevent anything freezing. The advantage is you can keep the air vent as fast as you want or need and let the TRV shut on room temperature.
  • Plumb Bob
    Plumb Bob Member Posts: 97

    Hanging plastic won't do much.

    But if you close off the area with two layers of drywall enclosing a layer of fiberglass insulation, plus insulate all the floors/ceilings/walls between the warm part and the cold part of the house, plus drain water pipes so they don't burst, then you'll save money.

    If it is (say) 70F in the house and 0F outside, is it really going down to outdoor temp (0F) in the closed-off area? If instead it is 60F, then that area is still being heated. With a sheet of plastic, it'll still be 60F.

    There is an added wrinkle. Heat loss actually doesn't depend on how much floor area is being heated; it depends on the the envelope (the outer perimeter of the space being heated). If you seal off a section of the house and let it get very cold, you change the envelope. The size of the heated area is smaller, but the perimeter of the heated area may be the same or even larger.
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