More Green Building Curmudgeon
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.
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8 Comments
Living the SE US I completely agree with Seville. For 20 yrs I've been dealing with nightly nose bleeds during the heating months (TStat set at 60-65F) or chilly summers because the AC is set low in order to pull humidity out of the air.
Sometimes I wish the house would get struck by lightening and "burn down" just so I could fix the damn place.
A couple of years ago, an HVAC contractor and I went to a client’s high-performing Dallas home, in July, and we found ourselves freezing inside. I asked why? She said, “We set the temperature at 68°F because we like to sleep under thick covers”, and she proceeded to show me, perfectly fitted for the North Pole. To add, this home has two 16’ quad-slider doors, and two 8’ sliders on the back of the house. Those doors are constantly open and closed, or left open, by their pool parting teenagers and their friends. They said, “Sometimes we have trouble maintaining the right temperature in the house”… REALLYYYY?
If we are talking comfort, can we stop telling people a single ductless minisplit is a good solution for comfort for anything but the highest performance houses (and even then...)? 3-7°F difference between rooms is not comfort. Efficient, yes. Cheap, yes. Comfort? Not so much.
Air to water heat pumps, with a properly designed hydronics system, you can get efficiency and comfort out the wazoo in most climate zones. :)
For a deep technical look, check out John Sieigenthaler's recent webinar series on youtube "https://www.youtube.com/watch?v=wga6WRNVs4w&list=PLuuV0ELkYb5Vz0Fu_J6iMTE2UDLwWMUi9" for a great example of what comfort and efficiency can look like in a normal, efficient house.
Better still, get him to write an article for you, what an excellent addition to this site that would be.
Agreed, let's start seeing room-by-room temperature and humidity logs.
Any advice about setbacks should account for the equipment used - single speed/fixed efficiency (vs load) or variable.
I don't have logs to show you, but I did monitor room to room temperatures when we first had our ductless heat pumps installed. We have one head per floor. The largest delta I've seen in my place, on a - 20°C night - our design temp - , was 2.1°C or 3.78°F. That evens out during the day.
My house measured at just slightly under 1 ach@50, has R60 attic insulation, R20 batt insulation in the walls, R20 ICF foundation, and no slab insulation. The place is ~2200sqft. No back up or supplemental heat was used. I don't have room to room humidity readings, the common consumer level sensors are way too inaccurate to make comparisons useful anyway.
Edit to add. Those readings came from the first year after we had a heat pump installed. At that time we had one on the main floor and still had resistive heat in the basement. The resistive base boards maintained nearly perfectly even temperatures. When we had the second heat pump installed in the basement, a year later we had it positioned so that it was more to the side of the house that was cooler. So if the main floor unit is a third from the right end of the house the basement one is a third from the left end.
I didn't monitor temperatures after the first year because I was very happy with things. But the positioning of the second heat pump seems to have evened out the temperatures on the main floor. It's not perfect, and I don't have an accurate number to give, but at least in my mind it helped.
Comfort is at least in part relative. When I mow the lawn on a hot, humid day in June, it always feels good inside, even if it's 80° and a little sticky, because I haven't broken down and turned on the AC yet.
How many people's comfort is dependent on seeing a certain number on the thermostat? Would 78° feel "hot" once they realized the thermostat wasn't set to 72°?
Comfort is extremely relative. I'm from Canada but travel sometimes for work. I've been to several places where I'm walking around in shorts and a t-shirt, sweating like crazy from the heat, while the locals have long sleeves and pants on because they find it cold. Conversely, I've also worked in engine rooms that got up to 65°C. (we wore ice vests and worked in 20 minute stints.) 45°C felt comfortable after a while of that. Back home and acclimated, now if it gets up to 25 °C I'm turning on the AC.
“I’ll take out a loan to pay my energy bill before I sit in my living room at 78 degrees” OMG! This is such a right true story, people can forget to pay their bills and sit in 78 degrees rooms and that is so bad for everyone, I don’t know how they are doing that because when I was trying to do that my mind exploded, and I just realize that I forget to pay my bills and I even took a loan https://northnloans.ca/no-refusal-payday-loans-canada.php to fulfil gap between paid and not paid bills, so it was like a real challenge for me. I currently without cash because I bought a new house that is so good that I lost everything on buying it!
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