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yesindeed Member Posts: 13
Hello All,
I have a two family house with a N.G. force heat unit (100MBH), the house was built over 50 yrs. ago. Both first and second floors have ducted vents that runs inside the walls. During the cold months (N.E.) region the thermostat is set to 72 deg. and it satisfies the first floor adequately however the second floor occupants complains that they are always cold. We contacted a HVAC company whom advised us to install a separate system for the second floor. Any advice will be greatly appreciated.


  • Jamie Hall
    Jamie Hall Member Posts: 16,067
    Upstairs ducts in the outside walls? I would be they either aren't insulated, or are insulated very poorly, if so.

    In any event, it is hard to get good balance in all seasons with forced air, unless one has powered dampers -- which introduce other problems, such as inadequate airflow through the furnace heat exchanger.

    A separate system may well be the best way to go -- but as I said in the first paragraph, find out which walls the ducts to the second floor run in, and if they are outside walls insulate them somehow. Or put the second floor unit entirely within the second floor -- or even in the attic, if that is insulated.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SWEI
    SWEI Member Posts: 7,356
    Is the attic insulated? If so, how well? Adding insulation to an attic is inexpensive and easy.
    JUGHNE Member Posts: 8,431
    If this was originally constructed as single family dwelling with open stairwell there might not have been any "cold" air returns on the second floor. If so then you are trying to push air upstairs with no way for it to return to the furnace.

    A separate upstairs system seems logical at this point, however the existing furnace might be oversized for the first floor alone.
  • Paul48
    Paul48 Member Posts: 4,470
    Contact an HVAC company that wants to find out what the problem is. What's the heat loss of the structure? Where's the cfm from the blower going? Any problem can be fixed by throwing a bucket of money at it. I don't have a bucket of money myself.
  • yesindeed
    yesindeed Member Posts: 13
    The Attic is insulated and it is a two family house. The stairwell leading to the second floor is not heated. there is (1) diffuser in the kitchen (3) diffusers in the living room and each of the three bedrooom has (1) diffuser. Bathroom has (1) diffuser. Most of the heat loss is through the duct (which are uninsulated). I was thinking of isolating the second floor from the main heating system and install a seperate system ie.. hydronic.
  • Paul48
    Paul48 Member Posts: 4,470
    The heat loss I was refering to, is the calculation of the number of btus required to heat the structure. The blower of the furnace puts out a certain number of cubic feet per minute of air. By measuring the cfm at each register, they can tell how much is being lost. Old, unsealed ducts, can leak like sieves. Add that to uninsulated, exterior walls, and there's no way it will work.
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