Brittle Power- PARTS 1-3 (+Notes) - Natural Capitalism Solutions

Chapter Fifteen: End-Use Efficiency: Most Resilience Per Dollar 249square-foot frame dwelling built in 1977 in Regina, Saskatchewan. 59 The site,at sixty and a half degrees North latitude, gets about a tenth less solar radiationper year than the U.S. average. The climate—nearly eleven thousandFahrenheit degree-days per year—is about half again as cold as Buffalo, NewYork, Manchester, New Hampshire, or Flagstaff, Arizona. The lowest temperaturenormally expected is minus twenty-nine degrees Fahrenheit.The walls of the house use offset double two-by-six-inch studs insulated toan R-value (a measure of resistance to heat flow) of forty. The R-value of theroof insulation is sixty. A heavy, carefully caulked vapor barrier reduces theuncontrolled inward leakage of air (infiltration) to less than five percent of acomplete air change per hour. An air-to-air heat exchanger provides threefifthsof an air change per hour—more if desired—while recovering eighty percentof the warmth in the exhaust air. The windows are double-glazed downstairsand triple-glazed upstairs, and are fitted with insulating night shutters.The door, like the foundation slab, is insulated, and there is a double-door“airlock” entryway.As a result of these highly cost-effective measures, all of which togetherwere repaid from fuel savings within the first few years, the total heat lossthrough the shell of the house is only thirty-eight watts per Fahrenheit degreeof temperature difference between inside and outside when the window shuttersare closed, fifty-five with them open. The gross shell loss totals only aboutforty million BTUs per year—the heat content of just over three hundred gallonsof oil. But after allowance for the “free heat” from the windows, people,lights, and appliances, the net annual space heating load is only five millionBTUs, or fourteen hundred kilowatt-hours—less than four percent as big as for anordinary house the same size in the same city. 60Furthermore, all the space and water heating needs of the superinsulatedhouse can be covered, without needing back-up, by a solar system with-onlyone hundred ninety square feet of collectors—less than ten percent of the floorarea—together with heat storage in thirteen tons of water (just over three thousandgallons)—less than three percent of the house volume. Most studieswould predict that five to ten times this collector area and storage volumewould be necessary to cover even two-thirds of the load. Why, then, can thesmaller solar system be big enough?The answer to this question reveals how profoundly the efficiencyimprovements have changed the basic physics of the house. An ordinaryhouse requires sharp peaks of heat to maintain its inside temperature wheneverthe weather turns even moderately cold. The rate of supplying heat atthese peak periods often exceeds ten kilowatts even in a mild California climate;61 in an ordinary Regina house they would be many tens of kilowatts.