Published on July 9th, 2008 | by Stephanie Evans
Eco Air Conditioning Ideas
Before there was air conditioning, human beings lived differently. In hot climates, in hot seasons, and at hot times of day, we changed our habits. We slowed down. We sat under trees or verandahs with fans and cool drinks. We took siestas and we slept out on our screen porches. We soaked our bandanas and wore them around our necks. But no longer…
With the advent of ubiquitous central air conditioning, we are now able to live in inhospitable climates like the low deserts of the Sun Belt. We dash from our cold homes to our cold cars and drive to our cold offices to work, all while the sun beats down relentlessly around us.
Many people enjoy living in sunny climates if they don’t have to experience their actual temperature, and they are willing to pay high electricity bills to do so. Like so many technological advances, the benefits are obvious, the drawbacks, less so.
The Hidden Costs
Air conditioning functions by means of hydrofluorocarbons, which are still, slowly, being phased out because they destroy the ozone layer of our planet. Air conditioning is powered by electricity produced predominantly by burning fossil fuels. The spectacle of people turning up their air conditioners to protect themselves from the global warming which those very air conditioners in part are causing is more than a parody of shortsightedness—it’s a tragedy coming true.
A recently published study in Geophysical Research Letters predicts such a response of energy use to global warming. As the Southwest and Southeast summers get ever-hotter, carbon emissions for cooling down the booming cities there will spike, unless some radical shift in understanding develops very soon. Even today, at least half of a typical U.S. household’s summer energy bill is devoted to air conditioning.
Reduced air exchange with the outdoors can substantially increase the level of mold spores and off-gassed chemicals that you breathe. Air conditioning has been shown to aggravate arthritis, neuritis, and sinus problems. People who live and work in constantly air-conditioned environments are more susceptible to upper-respiratory illnesses, in part due to the significant stress a body experiences when moving through extremes of temperature rapidly and to the air-borne virus circulation that an air conditioner promotes.
When our bodies become accustomed to, and dependent upon, artificial cooling, they have a much harder time coping with real summer temperatures than they would have otherwise. We become more reluctant to go outside, and avoid outdoor activity and exercise—a vicious cycle.
These are less measurable but nonetheless real. If no one walks anywhere because it is cooler to drive, if everyone lives sealed behind glass, our sense of community correspondingly suffers. Viewing the world outside of our air conditioned spaces as essentially “unlivable” creates a truly unhealthy relationship to the planet that sustains us.
To successfully create comfortable indoor environments with few or no electric inputs, it’s important to understand how heating and cooling work, both in your house and on your skin. So, here’s a little bit of physics. Heat is transferred via three different processes:
- Conduction is the passage of heat through a solid, such as your home’s roof, walls, and windows.
- Radiation is heat traveling in the form of light, both visible-spectrum sunlight and invisible, low-wavelength infrared.
- Convection is heat being carried in the air as it naturally rises and circulates.
Keeping the sun’s heat out of your home by, for example, insulating your roof, is controlling conducted heat. Putting up awnings so that direct sunlight doesn’t shine in your windows is an example of controlling radiated heat. Installing attic vents and fans so that heat rises and leaves your house through the roof is a way of controlling convected heat.
You can look at it from the opposite side too. You are cooled by convection when air moves over your skin as the warmer air rises and is replaced by cooler air from below. Good ventilation creates convection currents: the faster this air moves, the more refreshing it is.
If your surroundings are cooler than you are, you will radiate your own heat to them, cooling yourself. The cooler your environment, the more heat you will radiate.
For more tips and strategies about keeping cool, visit:
High Tech and Future Visions
Because air conditioning is such a large ecological problem, there are plenty of proposals for better ways to cool interior air. Some of these are already used in commercial buildings, and a few are even available for residential use.
Hydronic cooling, also called radiant hydronic cooling, is cooling by means of chilled water pipes rather than chilled air. It’s “radiant” because (back to the physics lesson) the heat emitted by the people in the room is absorbed by the cool water.
The most common residential delivery systems are via aluminum panels carrying concealed tubing mounted on the ceiling. If there is an existing hydronic heating system of tubes embedded in the floor, the same tubes can be used for both heating and cooling. The water is mixed with glycol and cooled by a heat pump, a cooling tower (in commercial buildings), or sometimes by means of well water or by passing underground.
Hydronic cooling can be difficult in humid climates, as the interior air must be fairly dry in order to prevent condensation problems. In some areas, combining them with an auxilliary air conditioning system (which dehumidifies) is a good solution.
New ways of dehumidifying are generating intense interest because most of the air conditioning energy used to cool buildings in humid climates is used to simply dehumidify them. Technology using desiccants, improved condensers and compressors, and even electrostatically-induced precipitation of water vapor are in development and trial phases.
Green roofs cool buildings (among their many other advantages), both by insulating from the sun and by evaporative cooling via plants giving off water.
These ideas are exciting, but the truth is, most of our home cooling needs can be addressed by simple, non high-tech changes in the way we build houses and live in them, and a bit of adjustment to the expectations we have for our personal comfort. With a bit of creativity, we can live without relying on air conditioning!