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It's the heat and the humidity
On reflective films, carbon nanotubes, and keeping people from dying in the heat
While they wax and wane in popularity, there are lots of ways to keep solar energy from entering a building. Shutters can be closed, blinds and curtains may be drawn shut, reflective films can be applied to windows. Shade trees can be planted, seasonal porches can be built on sunny faces, and solar shading can be added to building facades.
■ Likewise, there are lots of low-cost, low-energy options for circulating air within a structure. The government openly endorses ceiling fans as an energy-saving measure, certain historic home designs that can be mimicked today consciously exploit natural air flows for cooling, and it's even possible to assemble circulation systems that make use of solar energy to counteract the effects of solar heating.
■ But the long-cited wisdom is true: It's not the heat, it's the humidity that often makes the indoors uncomfortable during the summertime. And it's worth recognizing that summer heat deaths may be increasing in places that historically haven't been especially susceptible to them. This sets up an unpleasant paradox: Climate-related weather extremes may raise the stakes for finding new ways to help keep people cool, even as governments may try limiting how often the air conditioning runs.
■ The real prize, it seems, is in finding some way of reducing the amount of humidity in the air either passively or with minimal energy use. It really is the humidity that kills -- especially if heat waves hit more people more often.
■ Humidity is what particularly stops sweat from working to cool the body, and it's widely recognized that people can tolerate higher dry temperatures than humid ones: Just ask the Finns about the merits of the extra-hot dry sauna. It would be a great breakthrough for human welfare if technologists could find new and better ways to achieve that low- or zero-energy dehumidification.
■ Emerging technologies like that of carbon nanotubes show unusual relationships with water that could hold promise if science can exploit those new-found interactions. If heat is going to continue to threaten human health, then we as a species need to invest in aggressively seeking out new solutions to the root of the problem. Solar heating and air flow are generally solvable problems; it's getting the water out that sticks with us.