House plans: Two-story houses and air conditioning

    Can you really have too much air conditioning? Yes, actually, you can.

    Sometimes, people are so concerned with making sure that their homes are cool and comfortable that they buy an air conditioning unit with more capacity than their home actually needs. This is often an issue with two-story homes, since warm air always rises to the second floor.

    A two-story house is more difficult to cool than a one-story house, but it can be done. And there are a couple of ways to do it. But first, let's debunk an air conditioning myth.

    I need the most powerful air conditioner within my budget!

    You might, but you probably don't. In fact, if your air conditioner is created to cool more space than you have, you'll have moisture problems. Your AC will cycle on and off too quickly, and it won't run long enough to remove humidity from your home. The capacity is higher than you need, and that's a problem.

    Ideally, you should have an air conditioning unit that is just powerful enough to cool your home on the hottest days, and no more.

    That will allow your unit to have longer on and off cycles, and longer cycles means your unit will effectively remove moisture from your home.

    Another note:

    Manufacturers often advertise the SEER rating of an air conditioning unit. It's a good number to know, but if you're purchasing a unit, it's not the main thing you should be focusing on. The efficiency of a unit isn't the same as its capacity, so make sure you know both before making a decision.

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    Cooling a two-story home

    If you live in a two-story, or are interested in building one for various reasons (read more about the perfect house plan here), you probably know that air conditioning a house with multiple levels is a little different.

    Since hot air rises, there's really no way for the upstairs of a home to be as cool as the downstairs. It breaks the laws of physics! You can get close, though.

    There are a couple different ways, depending on the size of your space. The size is important because it lets you know how much capacity your air conditioner should have—not too much, but just enough.

    1000 square feet or less upstairs:

    You could have two outside units (one for each floor) but you might not need it for that space. A better solution could be to have one air conditioning unit, a thermostat on each floor, and a damper system that can divert cool air upstairs when you need it.

    1500 square feet or more upstairs:

    It is a good idea to have two units if the upstairs is larger than 1500 square feet. If you keep the upstairs one set to two degrees cooler than the downstairs one, the upstairs AC runs more, keeping it really dry, and the cool air migrates downstairs and takes care of the temperature there.

    Air conditioning is not one of those things where more is better. Make sure your unit has enough capacity to cool your home, but don't go overboard!

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