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How can I keep my second floor cool?

BARBRASH | Posted in General Questions on


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  1. GBA Editor
    Martin Holladay | | #1

    The last time this question came up -- here is the link -- this is what I wrote:

    "Older houses with your problem are best fixed by having two separate AC systems -- one for each floor.

    That doesn't mean, of course, that other contributing factors to your discomfort shouldn't be addressed first. All of these measures can help reduce the temperature difference between floors:

    1. Air sealing work in your basement and attic.

    2. Additional insulation in your attic.

    3. Exterior shading of west-facing windows, especially west-facing windows on the second floor.

    4. Adding dampers to the supply ducts serving the first floor (so they can be adjusted during the summer months), and making improvements to ducts serving the second floor. (Remember to re-open the dampers when cold weather arrives in the fall.)

    Even if you do all of these things, though, your second floor may well remain hotter than your lower floor. If you don't want to install a new split-system air conditioner serving your second floor, you might consider installing a ductless minisplit up there.

    For more information on this problem, see Keeping Cool in a Two-Story House."

  2. user-5946022 | | #2

    I will second Martin's suggestions of air sealing and adding (or using) dampers.You also need to make sure the dampers are installed to isolate by levels.

    I have experience with a 2 level home with one split system in the attic. The duct had dampers, but they were covered with the insulation. However, I could feel the handles through the insulation, and was able to access them. Remember, heat rises. Close the dampers serving the downstairs in the summer. All the ac will go upstairs, but cool air will also fall. If the t-stat is downstairs, it will cool until the t-stat is satisfied. This makes the upstairs a bit cooler than the downstairs, which usually works out ok because the bedrooms upstairs are used at a different time than the downstairs rooms. Do the reverse in the winter, closing the dampers to the ducts serving the upstairs. This method has reduced the ac/heat bills and increased the comfort of the two houses I have addressed it in, in a group of multiple homes all built the same way at the same time. Those who do not do the damper adjustment still complain of comfort issues...

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