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A couple questions about a hot room concept.

  1. Jan 26, 2014 #1
    A couple questions about a "hot room" concept.

    I had an idea that I may try to implement should I ever get around to building my dream house. I think of it as a "hot room". The idea is that there is a utility room which is positioned to receive most of the wast heat generated by household appliances. The radiator coils at the back of the refrigerator, the water heater, and the dryer exhaust would be vented to this room. It could also house a natural gas powered backup generator.

    This room would be insulated both from the living space and from the outdoors. In the summer the room would be vented to the outdoors, reducing the energy needed to air condition the living space. In the winter the room would be vented to the living space, reducing the need for heat.

    A couple of questions...

    1. I googled for "hot room" and found nothing like this concept. Is there another name for it? Surely this is not an original idea.

    2. The house I currently live in has a ventless natural gas heater. The combustion byproducts are vented directly into the room. The combustion is clean enough that the exhaust is not harmful. Could I expect the same exhaust quality from a natural gas powered generator? It seems like a shame to burn the gas and get only heat when I could get heat and electricity.
  2. jcsd
  3. Jan 26, 2014 #2


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    In the winter, the heat from the appliances could still be used to to heat your house directly and no need for the hot room. In summer, it might be a concept to look at, but you would have to look at the economic feasability, since you will be paying for a square footage of the room and extra fixtures. How long the return on investment from the initial outlay and yearly energy savings might be something to look at, but then you did say you would have a generator in the room, so the square footage should be a negligable part of the equation.

    Gas powered generator - carbon monoxide poisoning. That might be an issue even with your natural gas ventless heater. As well as oxygen depletion in the living space and humidity buildup.You might want to look into that.
  4. Jan 26, 2014 #3


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    Staff: Mentor

    1. How hot?
    2. That isn't safe. Even ventless heaters have fallen out of favor, but at least the combustion is typically pretty complete. With a generator, there will probably be some CO production.
  5. Jan 26, 2014 #4


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    In winter the hot room would contain hot air which will have higher humidity. There are some real disadvantages in using that air directly, because when it reaches the cooler house it will condense. You will need to use counter current heat exchangers to transfer heat to the internal air so you can control condensation. It is better to have the equipment in the house and so avoid the heat exchangers or mould growth on the ceiling.
  6. Jan 27, 2014 #5
    I would expect the hot room temperature to max out at no more then 20 F above the environment it is circulated with. The hottest it gets in the summer here is about 100 so 120 in the summer. I cant see heating to any more then 75 in the winter to that would make the hot room 95. If temperatures got hotter then that I would install larger fans to increase circulation and bring them down.

    If the generator exhaust would not be sufficiently clean to vent directly I could run it through a long exhaust pipe which would allow it to cool off by radiating heat into the room, then, once cool, vent it outside. I'm pretty sure this would work from an engineering standpoint, are there any building codes this would be in violation of?

    I had considered the condensation issue. In the summer it would be a non-issue because the room would be vented to outside. In the winter I was thinking of addressing it with a de-humidifier. It would use additional electricity but all the energy it used would end up as heat anyway so it wouldn't really be wasted in the winter.
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