The Thankless Plight of Thermostats

Perhaps no form of interactive technology is more infuriating than the thermostat. I’m not talking about fancy Nest thermostats, but this may apply to them as well. Thermostats actually have a very simple job, but the ways in which they have been incorporated into a larger HVAC system often cause serious problems.

Interactivity of a Thermostat

First off, it may be productive to establish just how interactive thermostats are. For the purposes of this post, we can assume that a thermostat is a temperature measuring device that receives an input from a user in the form of the desired temperature. When the temperature of the space falls outside of the desired temperature, it either heats the space or cools the space.

Would that it were so simple…

What makes it interactive? The user delivers an input in the form of a numerical temperature; the thermostat processes it and makes a decision to either heat or cool the space. It then engages in a productive feedback loop that allows it to check the temperature against the desired temperature and adjust accordingly. The user then feels the outcome (or output) of that interaction in the form of heating or cooling. So why does it feel like they never work?

Limitations of Thermostats

There are a number of factors that go into why thermostats don’t behave in the ways that we expect.* The first possibility is that it isn’t located in an area that it controls. If the thermostat can’t feel that the temperature that it’s affecting, it won’t know when to stop. This can create environments that are too cold in the summer or too warm in the winter. This is an error of the architect or mechanical engineer who designed the system, not a user error.

The second possibility is if the thermostat is responsible for too many different areas. It’s similar to the first scenario but the outcome results in microclimates. One area may be heated or cooled at a different rate than the others which would result in different temperatures. This is also an error of the architect or mechanical engineer.

The third scenario, however, focuses on the user. Unbeknownst to many who have operated thermostats, they actually have a range of temperatures that are considered acceptable. Built into the way a thermostat works is the principle that the ideal temperature is not a specific value but a range of acceptable values that bracket the desired temperature. That range is determined by how energy efficient the system is expected to be. It’s more efficient to allow the AC to run for a long period of time and rest for a long period of time than to intermittently turn on and off. This produces a more accurate climate but requires more energy. The result is a balance between the two scenarios.

Users often react to this by ignoring the temperature displayed on the thermostat and going simply off of feeling. The delay between an output from the heating or AC system may cause the user to overshoot the temperature they actually desire and will find them returning shortly thereafter to compensate and readjust.

How to Improve the Thermostat

One of the problems with thermostats is the lag between input and output. While decreasing this delay is possible it would ultimately result in a less energy efficient system if the AC turned on everytime someone pushed the thermostat up or down a degree.

An alternative means of providing more feedback would be to display the desired temperature as a range, with a specific temperature in the middle. This would allow a user to make a much more informed decision. Users rarely know that when they feel too cold or hot, they are still feeling a temperature that is within the acceptable range of temperatures. However, if they know that once they move the needle on the thermostat, there will be more temperatures that they will be subjected to that may be even more uncomfortable, they might choose otherwise.

For example, let’s say that a user is sitting in a room that is 70˚, and they are cold. Let’s also assume that the thermostat is set to 71˚. That user could raise the temperature to 73˚, but they may think twice about doing that if the temperature readout also informed the user that raising the temperature to 73˚ means the range would include 72˚ to 75˚.

More immediate and informative feedback does usually make for better interactivity. This is a quick fix which can buy some time for the mechanical engineers to develop better HVAC systems!

*Note: There are many other factors that can play into this dance that include but are not limited to the perceived temperature of the user based on their prior environment, equipment failure, shoddy air duct design and poor insulation.

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