The Montreal Protocol came into force in 1989. It bans the production and use of chemicals that have been shown to damage the ozone layer, a concern first raised by scientists in the 1970s. Without the protective ozone layer, we all would get skin cancer! Discovery of a persistent ozone hole over Antarctica in 1984 by British scientists highlighted the damage to the ozone layer and heightened public concern over the chemicals that were believed to be causing the phenomenon.109
These damaging chemicals include commonly used refrigerants, such as Freon and chlorinated fluorocarbons (CFCs). With the signing of the Montreal Protocol, chemical companies began research in earnest to come up with substitutes that would be as efficient as conventional refrigerants in cooling buildings (and everything else) without having any environmentally harmful side effects. The issue is simple: less-efficient refrigerants mean more electrical energy is needed to accomplish the same amount of cooling (engineers express it in terms of kilowatts of electricity per ton of cooling); therefore, more carbon dioxide emissions occur from fossil-fuel-fired power plants (the dominant US mode of producing electrical power), and more global warming occurs.
According to one expert, global warming and ozone depletion are both undesirable, and the two effects are negatively synergistic. Ozone depletion aggravates global warming, and global warming aggravates ozone depletion.110
The LEED system bans CFC use in "base building" cooling and refrigeration systems (excluding water coolers and small refrigerators) and also bans CFCs, HFCs (hydrofluorocarbons) and halons in fire suppression systems.
Better living through chemistry! What we have discovered this decade is that chemicals with high ozone-depletion potential generally have low global-warming potential and vice versa. So, the attempt to prevent ozone layer damage might inadvertently lead to higher levels of global warming. Recognizing this conundrum, the LEED system was modified a few years ago to allow some hydrochlorofluorocarbons (HCFCs), such as HCFC-22 and HCFC-123, in building refrigeration systems, so long as they have relatively low global-warming potential. Under the Montreal Protocol, HCFCs are not scheduled for a complete phase-out in developed countries until 2030.
When older buildings are being renovated, it's important to replace older air-conditioning and refrigeration systems with modern chillers and refrigerators using HCFCs that are relatively benign both in terms of global warming and ozone depletion. In new buildings, why not design them to operate whenever possible without mechanical cooling systems? In the maritime Pacific Northwest, relatively low humidity and cool temperatures allow properly designed buildings to operate on 100% outside air a good part of the year. In other areas of the country, particularly along the coasts and in higher elevations, passive solar design, operable windows, radiant cooling and natural ventilation strategies will allow systems to operate without mechanical cooling for months each year.
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