Why is it Warm Upstairs?

Have you ever noticed that it’s often hotter upstairs than it is downstairs? No, it’s not just your house, and it’s (probably) not your last contractor’s fault. Feeling warm upstairs is simply the result of the stack effect, which is a fancy way of saying that hot air rises.

Why Not Adjust How Air Conditioning Units are Built?

So we know why the stack effect makes the upstairs hotter—can’t we just design an air conditioner system that combats this by pumping more cold air upstairs and keeping it cooler? No. Here’s why: hot air rises not only in the summer but also in the winter. If you’re running the heat, with hot air rising in addition to the extra hot air you’re pumping upstairs, can you imagine how miserably blazing hot that would be? Not only that, it’s going to be too cold downstairs.

Is There an Actual, Plausible Solution to Warm upstairs?  

An A/C unit that pumps more air into the upstairs is out as a solution to a too warm upstairs in your house. There are other plausible solutions, but each one lacks practicality in its own way.

These solutions include:

  • Having two air conditioning units. That’s right, two A/C units in one house; one would serve only the upstairs, and one would only serve the downstairs. This is possible, but the downside is that you’re now looking at the cost of two A/C units. The bill and expense of running both, along with the maintenance and upkeep, will continue to cost more even after the investment of having it installed. For many, the cost keeps it from being a practical solution.
  • Installing a zoning system. A zoning system is a system that has what are essentially two different types of valves called dampers and actuators that can either shut off or turn on the air to different spaces within a house. The problem here: zoning systems don’t work very well, with a few very expensive, high-end options. When sectioning off air to certain areas, you can put too much air in too little space, which can cause system inefficiency and freezing. Like a separate A/C unit, it’s a whole extra unit that needs maintenance and can cause problems—and it doesn’t work well enough to warrant it. They can also be very loud, meaning you’re trading heat for a headache.
  • Utilizing a ductless solution. Ductless systems are incredibly efficient, so this is my personal favorite on our solution list. As you can imagine, they don’t require any ductwork, so it’s just a matter of running a small line set outside, allowing you to repurpose air into other places. The only real downside here is that it can put stress on the existing system, and it can be expensive to install.

Find the Option That’s Best for You

It’s hard to beat physics, and it’s harder to beat stack effect. The answer to the question, “Why aren’t air conditioning units designed to solve this warm upstairs problem?” is simple. There is no easy way to design them differently, at least not when addressing this particular problem. There’s a trade-off no matter what you choose, and with many of the options requiring extra cost, maintenance, and upkeep, plenty of homeowners will settle for the upstairs being a little warm.


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