What size (BTUs) air conditioners should I buy for my (sort of) open layout apartment

Discussion in 'HVAC Heating & Cooling' started by mizrachi, May 29, 2011.

  1. mizrachi

    mizrachi New Member

    Messages:
    10
    Location:
    NYC
    Our apt has an identical layout to this apartment, though a few feet bigger in all directions, and a pass-thru section between the kitchen and the living room. Our plan is to install 2 window ACs, one in the BR and one in the LR. The LR AC will need to compensate for the kitchen pass-thru and the BR AC will have to handle the bedroom door left open at all times (damn cats). So, how many BTUs for each? I'm thinking slightly larger for the LR but I'm unsure about numbers.
  2. DonL

    DonL Out of the Trades

    Messages:
    3,903
    Location:
    Houston, TX
    Having the dimensions of the rooms, Including ceiling height would help you to get a better answer.

    Have a great day.

    DonL
    Last edited: May 29, 2011
  3. mizrachi

    mizrachi New Member

    Messages:
    10
    Location:
    NYC
    The dimensions and layout are linked in the body of the message.
  4. DonL

    DonL Out of the Trades

    Messages:
    3,903
    Location:
    Houston, TX
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Window air conditioning is not an exact science, but for a starting point you can use a figure like 20 BTU per square foot. So a small 5,000 btu unit would handle the bedroom. For the total area of kitchen and l/r of about 400 sq ft, an 8000 btu would pencil out. Then you need to add for the heat of the kitchen..probably 2000 more btu, so put a 10,000 btu unit in the l/r. since the air will not readily circulate into the kitchen, you will find the l/r will be chilly, and the kitchen too warm. Ceiling fans or other circulators will help with that some.
  6. Dana

    Dana In the trades

    Messages:
    2,804
    Location:
    01609
    Without knowing the orientation, R/U values, air leakage rates, and shading factors it's impossible to put a number on it. Heat gain in an apartment is never a function of the square feet of living space, more a function of the amount of exterior surface area with direct sun, and air infiltration rates.

    In NYC the latent loads (humidity) will outstrip the sensible (temperature-only) loads several-fold. On a N facing apartment w/ air conditioned units both above & below you might do just fine with a dehumidifer rather than a window AC.

    If this is a unit that you own, not rent, a "ductless mini-split" system with continuously variable compressor & fan speed will be far more comfortable & cheaper to operate than any window shaker. Many can be set up to specifically control both humidity & temp.
  7. DonL

    DonL Out of the Trades

    Messages:
    3,903
    Location:
    Houston, TX
    AMEN Dana.

    Have a Great day.

    DonL

    P.S the only problem with a dehumidifier, is that they add heat to the room, where they are located. Jimbo was correct about appliances adding heat, That has to be considered too.
    Last edited: May 31, 2011
  8. Dana

    Dana In the trades

    Messages:
    2,804
    Location:
    01609
    Agreed- rare is the unit that can make it on dehumidifer alone due to the space-heating effects. Keeping the duty cycle low enough to avoid raising the temp too much depends a lot on the actual air exchange rates. But 78F, 45% relative humidity is pretty comfy compared to 75F, 65% RH.

    Mini-splits have come a long way in the past dozen years, even for heating in NYC & southern New England climates. (They're even meeting/beating geothermal heat pump efficiencies in many heating apps.)
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