Buildings have had central heating for only about 140 years, and they have had air conditioning for only about 80 years. For most of human history, people took comfort in winter from a stone fireplace — somewhere to heat up a kettle or warm one’s hands.
Once heating and cooling systems were developed, almost everyone wanted them. Why? Because people want to be comfortable.
Comfort is hard to pin down
What is comfort? Definitions vary. If you are camping and get caught in a rainstorm, you’ll probably find that a dry sleeping bag in a dry tent is extremely comfortable. If you are spending the day ice fishing, you may find that a plywood shack equipped with a tiny propane heater is extremely comfortable — especially compared to the guy outside who is sitting on a Sheetrock bucket in the wind.
ASHRAE has developed a standard (ASHRAE 55) that decrees that heating and cooling systems should maintain a building’s indoor temperature and relative humidity within a comfortable range: not too hot, not too cold, not too dry, and not too damp (see Image #2, below).
The Passivhaus standard takes a similar approach, while noting additionally that the interior of a building shouldn’t be windy or drafty, and that the temperature of all of the surfaces in a room (especially window panes) shouldn’t be so cold in winter that radiational effects make people uncomfortable.
Standards that define a range of indoor conditions leading to human comfort are useful. All such standards note that not all people have the same ideas about comfort. Human comfort depends in part on whether the person is active or at rest; whether the person is fully clothed or naked; and whether the person is young or old.
Even if these factors are carefully controlled, however, humans differ. If two similarly clothed people of the same age are sitting in a room, one might say “I’m cold,” while the other might say, “I’m hot.”
Because of this human variability, standard writers have to specify ranges for conditions leading to comfort.
A family history of comfort
If I look back a couple of generations, I can easily document how comfort expectations have changed in my own family.
My grandmother was born in 1904, and grew up in rural South Dakota in a leaky frame house that was so cold every winter that the family banked the foundation with manure in the fall. I imagine that her bedroom was often below freezing during the winter.
As far as I know, my parents both grew up in homes with central heating (although my mother’s family had an icebox, not a refrigerator). If they wanted to experience air conditioning, they went to the movies.
My first memories date back to the late 1950s, when my family lived in a house with single-glazed windows in Boulder, Colorado. I remember waking up on winter mornings to admire the swirling, flower-like patterns of frost on the windows. Our eaves were often loaded with icicles — a sign that the attic didn’t have much insulation — and when I was having a bath, my parents used to make me laugh by breaking off an icicle and putting it in the bathtub for me to play with.
When I was growing up, cars didn’t have air conditioning. We would drive with the windows open, sticking our heads out like dogs.
No one wants to live the way we did in the 1930s
There is no turning back the comfort clock. It’s perfectly understandable that people prefer their homes to be air-conditioned during the summer. But advances in comfort raise the question: when does the arms race stop?
Would any of us recognize a motel room from 1960? These days, when you walk into a hotel or motel room — assuming you’re not staying in a hostel that caters to backpackers — you get more than a just a bed. You get a very wide bed — maybe two beds — with more pillows than a person could possibly use. In the bathroom you’ll find enough towels for a football team.
If the hotel offered you a bedroom like the one you have at home, you’d probably be insulted. That’s the arms race in action.
Passivhaus levels of comfort
I have written several articles noting that the Passivhaus standard often requires investments that aren’t cost-effective — for example, investments in thick insulation, triple-glazed windows, and Zehnder HRVs. When I suggest that it might be possible to specify less sub-slab insulation, double-glazed windows, or a simpler ventilation system, Passivhaus designers often respond: “You don’t understand! It’s not about cost-effectiveness! It’s about comfort!”
Sometimes they’re right: for example, when temperatures drop below 0°F, it’s usually more comfortable to sit next to a triple-glazed window than a double-glazed window.
Other times, they’re simply wrong. There is no way that a human can tell the difference between 6 inches of sub-slab foam and 12 inches of sub-slab foam.
But in all cases, these Passivhaus designers fail to ask an important question: how much money should we spend on comfort? If you get a chill when you sit next to a double-glazed window, maybe all you really need to do is put on a sweater.
If we establish a standard that insists that no surface in a house should ever be more than 7 F° cooler than the indoor air temperature, we are assuming that (a) humans should never have to suffer the indignity of sitting next to a window that has a surface temperature that is 9 F° cooler than the air, and that (b) spending lots of money on very expensive windows to meet our comfort needs is a good use of the world’s resources.
Two kinds of envelope and HVAC measures
I love envelope measures (for example, air sealing work and increased insulation levels) and HVAC solutions (for example, ductless minisplits) that are cost-effective. If investing in one of these measures saves enough energy over its lifetime to exceed the cost of the measure, it’s a great investment. Everybody wins.
What about envelope measures that aren’t cost-effective, but increase comfort? These measures make sense for homeowners who want high levels of comfort and can afford to spend more money on their house than the average family. But these measures shouldn’t be considered “green.” They are luxury features, not necessities.
Should occupants never notice anything?
Some Passivhaus designers and radiant-floor enthusiasts aim to create a house where we never notice the temperature. The temperature and relative humidity of the air should always be perfect. The goal appears to be for the occupants to think, “I notice nothing.”
In this vein, Mark Eatherton, the executive director of the Radiant Professionals Alliance, posted the following comment to a GBA article about radiant floors: “Being comfortable means that you are not aware of your surroundings. … You are not hot, nor are you cold. You are not over humidified nor are you under humidified. Ideally, you do not hear your comfort being delivered. Simply stated, you are not thinking about it, and if you are, then you are not comfortable.”
If this goal is achieved, it’s far from clear that our lives have been improved. It turns out that there is a paradox at the heart of this quest for perfect comfort: once it has been achieved, our lives feel somewhat empty. Most Buddhists have a fundamental understanding of this phenomenon.
If all human beings want is freedom from heat and cold, it would be hard to explain why kids remember camping trips with so much joy. Kids seem especially to remember the exhilaration of camping trips where everyone got wet and cold — and then got so hot and sweaty that they couldn’t wait to jump into a mountain lake.
There are two aspects to the phenomenon I’m describing. The first is that unchanging blandness seems to depress the human soul, in the same way that many nursing home residents are depressed by a diet without any hot peppers or garlic.
The second aspect to this phenomenon is more subtle; it was examined in depth by David Foster Wallace in his hilarious book, A Supposedly Fun Thing I’ll Never Do Again. When expectations are raised, as they are by Mark Eatherton’s attempt to deliver a house where occupants are always perfectly comfortable, and as they are by the Passivhaus promise that indoor temperatures will be perfectly uniform, we are setting people up for dissatisfaction. Expecting perfection, homeowners notice the slightest draft, and the slightest draft becomes irritating.
We can be comfortable if we are willing to accept the world as it is
Designers and homeowners need to remember that it is sometimes OK to live in an imperfect house — one that feels a little hot in July and a little cold and drafty in January. In fact, this type of imperfect house might be more affordable (or even “greener”) than an expensive Passivhaus.
When you’re hot, it might be time to drink a glass of lemonade. When you’re cold, it might be time to put on a pair of fuzzy slippers and brew a pot of tea. After all, summer is supposed to be different from winter.
If you take this approach, you might discover that your imperfect house is fine just the way it is.
Martin Holladay’s previous blog: “Building a Foam-Free House.”