Why do most folks set their thermostats lower in Summer than in Winter?
I’ve seen summer settings at 68°F (20°C), while winter settings are at 75°F (24°C). What do they expect the HVAC system to do when it senses an indoor air temperature of 72°F (22°C)? Should it heat the room? Cool it? It’s a paradox.
Engineers who design thermostats have a simple solution for this paradox – they let the user figure it out. They provide a Cool/Warm setting, which tells the device which setpoint is active.
This doesn't make sense to me. Not only is it a paradox, but it defies the way people perceive air temperature.
For example, if it’s 18°F (10°C) cooler inside than outside, you should feel much cooler when you step inside. So if the outside air is 91°F (35°C), you should feel much cooler with a summer setting of 77°F (25°C). And if the humidity is even slightly elevated, it will feel even hotter outside and cooler inside.
Similarly, if it’s 36°F (20°C) warmer inside than outside, you should feel much warmer when you step inside. So if it’s freezing cold (32°F or 0°C) outside, you should feel much warmer with a winter setting of 68°F (20°C).
But it seems that people no longer trust themselves to acclimate. Heat has been a standard offering in automobiles for over 50 years – it’s free, a by-product of the combustion engine. The default setting in wintertime is maximum heating, even though the riders wear coats. And nowadays, nearly every automobile has air conditioning, and the default summertime setting for it is maximum cooling. Climate control in automobiles mostly is “open loop,” meaning that the system does not monitor the air to see whether the setpoint has been reached. It just keeps heating or cooling.1 This is in opposition to indoor heating systems, which are closed loop.
The other drawback to the “low setpoint in summer, high in winter” method is that it’s more wasteful. It’s like biking uphill into a headwind.
Here’s where I brag about the setpoints I use – feel free to roll your eyes.
In summer, I’m fine with the window units set to 77°F (25°C). However on cool humid days, I might switch the units to dry mode, even though it doesn’t work as well as a dehumidifier. In Winter, I use a setpoint of about 64°F (18°C). Plus it drops an additional 2°C (or 3.6°F) at night in “setback” mode.2 Usually I get up before the furnace turns itself back on, so I experience a warming as I prepare tea / coffee, feed the cat, etc. That slight warming helps me acclimate to Winter.
Would you like to save money and reduce your ecological footprint?5 Then try this:
If you live alone, try a higher setpoint at home in summer. Wear a light sweater at work or while shopping. Limit the use of A/C in the car. And in winter, do the opposite. Try setting a lower setpoint at home, dress lightly in layers. When in the car, remove outerwear and limit the use of heat.
1 Some luxury cars provide closed loop climate control. Indeed, I drove an old Audi whose heat and air conditioning seemed to stop working after about twenty minutes. I don’t really know whether they were closed loop or was just broken. Either way, it was difficult to get used to the effect.
2 It’s a German-made boiler, which means the fundamental temperature units are Celsius. It provides a Fahrenheit display for most things, but not for the setpoint, which is “programmed” by setting DIP switches 3 on the thermostat’s circuit board.
3 A DIP switch 4 or Dual In-Line switch is really a set of switches packaged into the standard outline of an IC. And while ICs have gotten 60% smaller over the past three decades, DIP-switches have retained the same bulky outline of the chip packages they were modeled after.
4 https://en.wikipedia.org/wiki/DIP_switch
5 What is Ecological Footprint? Click here: https://en.wikipedia.org/wiki/Ecological_footprint
6 Try the footprint calculator at https://www.footprintcalculator.org/
