Load Calc and Basement Heating ?'s
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  1. #1
    Join Date
    Dec 2004
    Detroit, Michigan


    Running through the HVAC-Calc program before I get estimates for a new furnace, and have a couple of questions.

    Our basement is not really heated - there are a few vents down there but we keep them shut off. Temp usually hovers between 55 and 65 depending on the season. When running through the calcs I assume this would be considered an unheated basement even though there are a few registers down there?

    I also assume I don't need to include the basement itself in the load calc - unless we had intentions of running more duct work and fully heating the basement?

    And finally - we eventually plan to finish off the basement (1800sf). Right now I really don't have intentions of ever keeping the basement heated all the time but would put some type of supplemental heating down there - possibly electric basboards? Would it make sense to do that or size the new furance to be able handle the basement. That seems to me like it would be a waste unless you planned on using the basement as a fulltime living space - plus you'd have to add zoning right?

    What do you guys think?

  2. #2
    You should be able to treat the mainfloor as being above an unconditioned space at the temperature you figure that basement will be in the dead of winter.You would also have to enter the 55 or 60 degrees as the temperature you are maintaing the basement at.

    With the program you can re-run the calculation to see how much heat is needed to keep the basement at room temperature, it is probably a smaller penalty than you think.

  3. #3
    Join Date
    Apr 2004
    It seems every house in this area (N.Eeast Metro Area) has a basement so this question always comes up. Basically it comes down to your future intentions with this space. There is little reason to worry about A/C when the temp does't make it over 65 down there in August but heating is another animal all together. If you are plan on using the room regualrly, even for laundry and some storage, determine the heat loss per Manual J and compensate with the correct heating CFM.

    If you're asking whether to count the floors above it as, "over conditioned space" or "over non-conditioned" basement during a current heat calculation, it sounds to me that if your vents are closed off anyway, the latter scenerio is your likely answer.

    Since you plan on using the basement in the future as living space, why not size the furnace to be able to handle it...especially if your only other alternative is electric baseboard. Certainly you can rough in the ductwork now, even though the room is at present, unfinished. To avoid wasting energy, it's extremely important to design the ductwork properly (ala ACCA's Manual D)so that it meters the correct CFM now, while ceilings and walls are open. Ambient heat will only creep up through the first floor anyway, mitigating the heat loss from the first story.

  4. #4
    Join Date
    Dec 2004
    Detroit, Michigan
    Good points...you're right, I bet the heat loss will be less than I first thought since with basically no heat now it doesn't go lower than about 55 in the winter. I guess the main difference between the basement and first floor is that in the basement the space above the ceiling is conditioned, and the temperature differential between the inside of the basement and the outside of the basement walls is not that great - (except for the 18" or so above grade).

  5. #5
    Join Date
    Apr 2002
    You probably have uninsulated metal ducts down there that are losing heat to the basement as well and possibly cold floors on the mainfloor, (unless you insulated the floor joists).

    When you do finish the basement, add some insulation down to at least a couple feet below grade.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.


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