I recently pulled out the notes I made last year about a kerfuffle that arose after a writer quoted a decade-old ENERGY STAR publication titled “A Guide to Energy-Efficient Heating and Cooling.” In the guide, recommendations for thermostat set points included 70°F in winter and 78°F in summer, with 7°F to 8°F setbacks when away, and 4°F to 8°F setbacks when sleeping.
It isn’t clear to me exactly how the Twitterverse got started on the information that got everyone’s panties in a twist, but articles in People Magazine and The Hill both covered the reactions to the set point suggestions, and some of them are pretty amusing—a selection of comments include:
- “Dear Feds, kiss my ice-cold ass”
- “If you prefer a sleeping temperature that’s warmer than your daily room temperature you’re a lizard person, that’s just science”
- “If you sleep with your thermostat on 82 degrees you need to see a doctor”
- “No thermostat should be over 73. Also, why turn it up when you leave, does the dog really want it to be hot?”
- “I’ll take out a loan to pay my energy bill before I sit in my living room at 78 degrees”
- “I’d honestly live in aisle 4 at my local freezing-cold Giant before I ever consider 78 degrees while I’m home or 82 while I’m sleeping”
The EPA responds
In response, the Environmental Protection Agency (EPA) had this to say:
The ENERGY STAR program has not released a report on this topic. The ENERGY STAR program is not recommending that thermostats be set to 78 degrees F or any other temperature during the cooling season. In order to save energy, the ENERGY STAR website recommends owners of programmable thermostats increase the air conditioning temperature setting by 7 degrees F when homes are unoccupied and by 4 degrees F when occupants are asleep. The website illustrates this approach with an example of pre-programmed, energy-saving temperature settings in some programmable thermostats (which includes a 78 degree F setting). All thermostats are designed to allow for adjustment to ensure personal levels of comfort when people are in the home.
Average homes are the problem
Sitting here in Georgia in May (when I started writing this post), with an unseasonably cool 69°F at 1:00 pm along with 89% relative humidity outside, making it a bit of a challenge to keep things comfortable inside, the responses to the EPA make me wonder how we can manage comfort and efficiency for the average American.
I keep my (well air sealed) house at 78°F during most of the cooling season and it is very comfortable because the humidity is well controlled. I also use ceiling fans, turning them off when not in the room, improving comfort in warm weather, and even making it feel a little chilly at times. But this is not the average American home.
Far too often I run into people who can’t imagine keeping their air conditioning set at 78°F (or their heat at 70°F). I have consulted with people building homes who like to crank their AC down to the low 70s in the summer and sleep under a pile of blankets. In mixed and humid climates, most people don’t understand that indoor humidity levels are the big problem.
In a typically leaky house, as the air conditioner removes interior moisture, it is quickly replaced by outside air infiltration to balance the moisture level in the air, requiring a lower thermostat set point to maintain comfort. Conversely, in cold dry weather, interior moisture ex-filtrates to the exterior leading to dry indoor air, often remedied with humidifiers. Unfortunately, extensive air sealing is not in the cards for the average homeowner, leaving most people with no choice but to over-cool in the summer and run humidifiers in the winter to remain comfortable.
Setbacks, and defining comfort
I find it interesting that ENERGY STAR promotes thermostat setbacks as much as they do. There are a few problems with setback thermostats. The first being that most people don’t know how to use them properly. In fact, many senior apartments we work on avoid installing them because the residents can’t manage them. Second, in high performance homes, there is minimal savings in adjusting the set point. They do have some value in average homes, but only if they are used properly.
And who is to say what’s comfortable anyway?
ASHRAE Standard 55-2017: “Thermal Environmental Conditions for Human Occupancy” aims to specify the specific indoor conditions that would be considered acceptable by a majority of the occupants of a space. It includes the metabolic rates of different human activities, the insulation values of various types of clothing, and formulas to determine what combinations of temperature, humidity, air movement, and solar gain are required to maintain comfort for various activities and dress. Understanding the document is well above my pay grade, but the general range of comfort ends up around 30% to 60% relative humidity and 68°F to 75°F in the winter and 75°F to 80°F degrees in the summer.
Even within those ranges, will everyone be comfortable?
Better buildings and homeowner training
The first step to getting homeowners to manage indoor temperatures is to get them into well-built homes and apartments with efficient and effective HVAC systems—a tall order given the state of the construction industry. Once we have solved that problem, people will have to relearn how to set their thermostat, wear appropriate clothing, and use fans and solar gain appropriately. Unfortunately, with relatively low energy costs and a general attitude of “I want what I want,” I expect we will continue to see many extreme thermostat settings.
-Carl Seville is a green builder, educator, and consultant on sustainability to the residential construction industry. After a 25-year career in the remodeling industry, he and a partner founded SK Collaborative.