Spotlight Feature: Climate Control Ponderings
Let's talk for a minute or three about climate control in single-family homes.
(Just to be clear, by "climate control" I normally mean heating, cooling, humidity regulation, and air filtration, even though I'll talk about only the first two in this article. I should also point out that I live in the northern part of the U.S., so my perspective is skewed towards environments that have "real" winters, e.g. temperatures continuously below 32F for days at a time and significant yearly snowfall, and summers that are hot and humid enough that you wouldn't want to endure them without air conditioning if you had a choice, even when they aren't as warm as the current one has been.)
Clearly the two biggest energy consumers of those four climate control functions are heating and cooling, which provide four states of interest:
The outside and inside temperatures are both colder than the desired interior temperature, so heating is required: "cold winter".
The outside and inside temperatures are both hotter than the desired interior temperature, so cooling is required: "hot summer".
The the interior temperature is close enough to the desired level that no heating or cooling is needed: "mild spring and fall".
The interior and exterior temperatures fall on different sides of the desired interior temperature: "cool summer night after a hot day". (Yes, I'm ignoring the opposite condition, since it's much less common.)
"Mild spring and fall" is the easiest case to deal with--you open or close windows, as needed, and you stay acceptably comfortable with no additional energy consumption.
"Cold winter" days are, at a first pass, very simple: You strive to generate and distribute heat within the structure as efficiently as possible, and then minimize energy waste by optimizing your home's insulation.
"Hot summer" days are a little more complex, as not only do you have the issues of efficiency of energy consumption and insulation, but you also have to take into account strategies for minimizing the energy needed. Your goal is not simply to keep your house at a given temperature, but to remain acceptably comfortable. If it's mildly hot but very humid, do you air condition the whole house or just knock down the humidity in the room or rooms where you'll be, whether awake or asleep, with a dehumidifier? Can you get by with a little air conditioning (or none at all) and rely on fans? How often can you bear to go to the mall and shop for nothing, just to stay comfortable?
"Cool summer night" is a scenario that I alluded to, if not by that name, in a prior Spotlight installment when I talked about using one or more fans and strategically selecting which windows to open to create an exhaust effect that will efficiently cool a house. This general approach--using ambient conditions whenever possible to greatly reduce the energy consumed for climate control--is one that unfortunately gets far less attention than it should. It's probably one of the areas with the biggest potential for home energy savings available, and in an age of dirt-cheap microcontrollers that can manage everything from your thermostat to your microwave oven to how well your car's engine runs, it's an opportunity for energy savings that's just waiting to be exploited.
If your home already has a forced-air climate control system, you would need a microcontroller and control panel (basically a tiny computer that looks very much like a modern programmable thermostat), internal and external temperature sensors, and an external air pipe leading into the blower of the heating/cooling unit. When the controller sensed that the interior temperature was higher than you desired and that the outside temperature was at least some critical number of degrees cooler than the desired temperature, it could turn on the blower unit, open the exterior air inlet, and cool the house without running the air conditioning. Now, in environments that have significant winters this would require some intelligence in the design of the external air inlet to reduce energy loss during heating season, but that's not a showstopper.
Sound far fetched? I don't think so, especially since a conceptually similar system has been in use in the U.S. (and likely many other places) for decades--whole-house fans. These are large fans that mount in the ceiling of the top floor of the house and blow up into the attic. On a cool summer night you open windows in the house, turn on the fan, and it exhausts the hot air from the house and pulls in cooler air. It's a manual system, and some of the fans I've seen are a bit noisy, but it's also very effective under the right circumstances and far more energy efficient than air conditioning. The more automated system I described above is just a fancier version that would appeal more to people who have grown up with "set and forget" air conditioning.
In a larger sense what I'm arguing for here is a rethinking of home energy usage, one that moves away from the current brute-force mindset to one that better exploits natural conditions. On a hot summer day, how much energy in the form of sunlight falls on the roofs of the homes in the average neighborhood, energy that not only isn't collected and exploited, but actually causes us to use more energy to cool those homes? How much wind energy and, on the oceans or even on larger lakes, wave energy, is ignored, especially during the winter? How much geothermal cooling in the summer, or heating during the winter, via ground-loop heat pumps are we foregoing?
Please note that I'm not making a moral judgment about how we use energy. I'll leave that sort of holier-than-thou/"we're all going to die a miserable death because we deserve it for what we've done to the planet" crap to the apocalypticons. The current patterns of energy use in the industrialized nations have evolved in a world of plentiful, extremely cheap fossil fuels, and I'm sure any other group of societies would have done basically the same thing faced with the same circumstances; we're no better or worse than anyone else. But with energy prices rising, and likely to rise far more in the coming years, it's time for us to revisit our practices and look for ways to conserve energy.
I'm also not saying we should all become neo-green extremists, informed more by some flavor of Eastern mysticism than our various current cultural imperatives (not that there's anything wrong with that; more people reading about Buddhism, and doing so with an open mind, would do a lot to improve this world, in my opinion). I'm merely suggesting that we should make a serious effort to look at our energy consumption patterns with fresh eyes, to question everything, from our assumptions about our "needs" to the technology and energy sources we use to our daily habits, and make changes wherever possible to work more intelligently with our surroundings and benefit from them instead of burning so much energy to fight them.
Yes, doing this will take work and it will entail up-front investments, but in the long run it will benefit everyone--we'll individually save money, humanity will reduce its consumption of non-renewable energy, and the world will be less polluted. So, what the hell are we waiting for?
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