We have a hot water baseboard furnace heating system. It all works well except for that one room gets way too hot if we are to keep temperature in all the other rooms.

This particular room is the only bedroom on that floor and is the first on the hot water circuit for as well. The room is also the only bedroom on the floor and when the heat kicks in early in the morning that bedroom turns too hot very quickly. Since it's a bedroom keeping the door open is not an option. Keeping the window open is of course possible, but I do not think the occupant wants that due to traffic noise. He also works nights and sleeps part of the day which makes this even harder.

Is there any way to limit heating output for that one room without affecting the rest of the floor without open windows or door?

  • A proper system would have a control valve to regulate the flow rate into the heating element for each room. I imagine there is a shunt bypassing each heating element and some sort of throttling valve to allow more or less hot water into the radiator for that room. It sounds like that valve is not closing and so allowing too much water to flow through it. Nov 4, 2020 at 22:27
  • Thanks! I will look at it again, but if I throttle in that room won't that effect other rooms also?
    – Christian
    Nov 5, 2020 at 0:06
  • There must be some sort of balancing of the heat flow into each room. I thought it would be by regulating the hot water flow rate into a given radiator, but @Ecnerwal points out that in some systems the balancing could be by regulating air flow through the heat exchanger. Nov 5, 2020 at 1:47

2 Answers 2


Most hot water baseboards have a "flap" which can be used to regulate the heat output so the system can be balanced, since there are often long runs serving multiple rooms.

The flap can be opened for maximum airflow and heat delivery, or closed to minimize airflow and heat delivery. If there is no flap, or that is inadequate to resolve the problem, you can block the airflow by other means, such as placing towels to block the airflow (on a hot water or steam system only, where there is no risk of fire from blocking the radiator.)


If you can't reduce the overheating in that room by any of the ways the other guys suggested, you might want to wrap the heating element with aluminum foil. Start with wrapping about 2 feet see the results and wrap more in 2 feet increments until you achieve the desired room temperature. The foil does not have to be wrapped completely around the element but can cover the top and both sides.

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