turn off radiators in unused rooms?

January 11, 2007 3:52 AM

How can I turn off a hot-water radiator to avoid heating a room I never use?

I've got three bedrooms I rarely use, and I would like to be able to "turn off" the radiators in those rooms. My understanding is that if you just turn one off, you're also turning off everything downstream from that radiator. Is there a way to install a bypass so that you can block the water from the radiator and allow it to chug on down to the next station on the line? If so, cost range?

I googled +radiator +bypass unused and I found this but I don't trust it.

posted by stupidsexyFlanders to home & garden (20 comments total)

That's a bizarre answer your google search turned up. I'd say half of the apartments I've lived in were old water-radiator-heated monsters, and we often had one or two off while the others pumped out heat like wood stoves. Never did turning one off cut heat to any of the others.

Just my experience, though. I know little about the workings. Why not try it? Just don't turn it half off. It's all the way one way or the other.
posted by dreamsign at 4:02 AM on January 11, 2007

you're also turning off everything downstream from that radiator

It depends on how the radiators are piped. If you have a diverter tee setup, you can turn off a radiator w/o turning off the radiators down stream.

Alternatively, you could put blankets over the radiators in the rooms that are too hot.
posted by malp at 5:19 AM on January 11, 2007

If the radiators have the little knobs for turning them on and off, that certainly shouldn't affect the other rooms. If you can, try it and see what happens, but, like dreamsign, I'm disinclined to believe that it will affect other rooms. If you are capable of doing something at the radiator to turn things on or off, I would bet that by turning one off, you do nothing to the others.

If the downstream thing were the case, it also seems like by turning one off, you'd be turning off the entire system, and you'd probably have to do that at the furnace level. Only "downstream" doesn't make any sense, because furnaces use water flow to carry heat, and if you block off downstream, than the flow would get pretty wonky.
posted by that girl at 5:37 AM on January 11, 2007

Only "downstream" doesn't make any sense, because furnaces use water flow to carry heat, and if you block off downstream, than the flow would get pretty wonky.

Nether the less, if you have a loop system, that's what will happen.
posted by malp at 5:42 AM on January 11, 2007

that girl, never mind, you're right.
posted by malp at 5:48 AM on January 11, 2007

If you get the radiators turned off successfully, remember to seal the doorway and insulate it (by hanging a quilted blanket or something). The walls and doors between interior rooms have effectively no insulation and you'll leak a huge amount of heat into the unheated spaces.
posted by ardgedee at 5:54 AM on January 11, 2007

It would be a pretty strange system that didn't allow you to turn off radiators individually. Turn it off. You'll probably need a wrench or pliers or a screwdriver, depending on the design.

While you're at it, you should also bleed the other radiators in the house -- open each radiator's valve long enough to let off steam. Start with the radiator farthest from the furnace and work in. Use something (a jar or bowl or whatever you have handy) to catch any water that seeps out while you're bleeding. When it stops blowing air and starts blowing all water, you're done with that radiator. Tighten it back up and move on to the next one.

Then make sure the system has the proper water pressure. There should be a gauge to show you whether it's in the right range. Don't go over the recommended limit.

Now insulate the rest of your home from the chilly rooms. Try tape if you aren't going to be going into them, or rubber door seals if you are. If you really aren't going to use that room for some time, you can add to the insulation between the cold door and the rest of the house by moving a bookshelf or something similar in front of the door to take advantage of the space, then slide an old blanket or sleeping bag or quilt down between the back of the book shelf and the door.

However, if you plan on using a cool room frequently (perhaps as a storeroom or pantry), maybe add a second door to the room (one opening in and one opening out).
posted by pracowity at 6:18 AM on January 11, 2007

We have steam radiators in a one-pipe system, but I can't see how/ why one would ever affect any others. Just make sure you close the valve completely. You don't want to leave it partially closed.
posted by yerfatma at 6:35 AM on January 11, 2007

You can also install individual thermostats on some radiators. Assuming that the system is not a single loop, the thermostatic controls would allow you to balance the system. Unfortunately they can cost upwards of 150.00 each plus installation.
posted by Gungho at 6:58 AM on January 11, 2007

This is a hot water radiator, not a steam radiator, if that makes a difference.
posted by stupidsexyFlanders at 7:03 AM on January 11, 2007

Try turning it off and see if it turns off any other radiators. It probably won't. If it does, just insulate this radiator so that little or no heat escapes into the room. You will use a wee bit of energy keeping the insulation warm, but will save quite a bit compared to letting it radiate into the whole room.
posted by caddis at 7:17 AM on January 11, 2007

Just do it. When you go home tonight, turn the silly thing off, eat your dinner, and then go back and check all the radiators to see how hot they are. There's a 99 percent chance that that's all you'll have to do. If it doesn't work -- if all of your other radiators also go cold -- then start worrying about how to get around the problem.
posted by pracowity at 8:09 AM on January 11, 2007

Also: Bleeding radiators can smell. So, although it's a good idea to do and can definitely help heat things more efficiently (water is better at heating than air--specific heat of 4.x as opposed to 1.x), it might be a little stinky after you do it.
posted by that girl at 8:27 AM on January 11, 2007

Just in case you're confused, bleeding is for water radiators. It gets the air that accumulates in them, out of them.
posted by that girl at 8:31 AM on January 11, 2007

I live in a 3 story victorian house built more than 100 years ago. I have hot water radiators in every room. There is one thermostat. When I turn off a radiator in an unused room that room gets cool. And it has no effect on any other room.
posted by JayRwv at 8:43 AM on January 11, 2007

Warm air can carry a great deal more water vapor than cold air, and with radiators and their pressure relief valves, your house may have even more water vapor in the air than it otherwise would, so when that warm moisture laden air seeps into those unheated rooms, as it inevitably will, condensation will occur, and before you know it, you will have mold in those rooms.

You could use dehumidifiers, but three rooms makes that a pricey solution.
posted by jamjam at 8:47 AM on January 11, 2007

Mold, in winter? I doubt it. Even with the extra moisture from the radiators the humidity is likely to be far less than in the summer, plus mold will grow less aggressively at colder temperature. Also, hot water rdiators don't release moisture unless they have automatic vents, and unless you have an air leak those vents should almost never open.
posted by caddis at 9:02 AM on January 11, 2007

You may also consider getting a thermostat for it, just in case. You don't want it to freeze.

See here. Sorry for the British link, but it's enough to get you on track at your plumbing supply store.
posted by kc0dxh at 9:40 AM on January 11, 2007

Mold, in winter? I doubt it.

According to this document (PDF, P.43), caddis, prepared by the U. S. Dept. of Housing and Urban Development and titled Heathy Home Issues: Asthma it is important to heat all rooms in winter to avoid moisture problems and mold growth.

If you had taken a moment to look over the OP's previous questions, you might have noticed this question about dehumidifying a basement, in which the OP states: "My disgusting basement is exceedingly damp...PS the basement floor (concrete slab) seems always damp, I guess that's where the humidity is coming from (high water table)."

Clearly, the OP has a moisture problem in his home already (assuming this is the same house, which seems to be a reasonable default assumption given his questions), and very probably considerable numbers of mold spores throughout his house.

As far as moisture in the air is concerned, even without any venting from the heaters, lots of moisture goes into the air in a typical house:

* One person’s breathing produces 1/4 cup of water per hour.
* Cooking for a family of four produces approximately five pints of water in 24 hours.
* Showering puts 1/2 pint of water into the air.
* Bathing puts 1/8 pint of water into the air.

Adding only four to six pints of water to the air raises the relative humidity in a 1,000 square foot home from 15 to 60 percent, assuming the temperature is constant.

As I said above, warm air can hold much more water than cooler air, 72F air can carry approx. twice as much as 50F air, for example, and the curve rises rapidly from there. Since this house appears to be in the Phialdelphia area, a 20+ degree differential between the air in the main body of the house and air in closed unheated bedrooms, especially next to outside walls and windows in winter, would seem to be the least one could expect.
posted by jamjam at 12:41 PM on January 11, 2007

That was spooky. Everything you said is true except for the part about how chocolate makes the soles of my feet itch.

Thanks for all your help, I'll try out these ideas.
posted by stupidsexyFlanders at 7:47 PM on January 11, 2007