Environmental Problems, Their Causes, and Sustainability 1

compacted bales of low-cost straw and then coveringthe bales on the outside and inside with plaster oradobe. The main problem is getting banks and othermoneylenders to recognize the potential of this andother unconventional types of housing and to providehomeowners with construction loans. (See theGuest Essay about strawbale and solar energy housesby Nancy Wicks on the website for this chapter.)Ecoroofs or green roofs covered with plants havebeen used in Germany, in other parts of Europe, and inIceland for decades. With proper design, these plantcoveredroof gardens provide good insulation, absorbstorm water and release it slowly, outlast conventionalroofs, and make a building or home more energy efficient.Designing and installing such systems could bean interesting career.How Can We Save Energy in ExistingBuildings? Stop Leaks and Use Energy-Efficient DevicesWe can save energy in existing buildings byinsulating them, plugging leaks, and using energyefficientheating and cooling systems, appliances,and lighting.Here are some ways to save energy in existingbuildings.■ Insulate and plug leaks. About one-third of heated airin U.S. homes and buildings escapes through closedwindows and holes and cracks (Figure 18-14)—roughly equal to the energy in all the oil flowingthrough the Alaska pipeline every year. During hotweather these windows and cracks also let heat in, increasingthe use of air conditioning. Although not verysexy, adding insulation and plugging leaks in a houseare two of the quickest, cheapest, and best ways tosave energy and money.■ Use energy-efficient windows. Replacing all windowsin the United States with low-E (low-emissivity) windowswould cut expensive heat losses from houses bytwo-thirds and reduce CO 2 emissions. Widely availablesuperinsulating windows insulate as well as 8–12sheets of glass. Although they cost 10–15% more thandouble-glazed windows, this cost is paid back rapidlyby the energy they save. Even better windows willreach the market soon.■ Stop other heating and cooling losses. Leaky heatingand cooling ducts in attics and unheated basementsallow 20–30% of a home’s heating and cooling energyto escape and draw unwanted moisture and heat intothe home. Careful sealing can reduce this loss. Somedesigns for new homes keep the ducts inside thehome’s thermal envelope so that escaping hot or coolair feeds back into the living space.■ Heat houses more efficiently (Figure 18-15). In order,the most energy-efficient ways to heat a space are:superinsulation, a geothermal heat pump, passivesolar heating, a conventional heat pump (in warmclimates only), small cogenerating microturbines, anda high-efficiency (85–98%) natural gas furnace. Themost wasteful and expensive way is to use electricresistance heating with the electricity produced by acoal-fired or nuclear power plant (Figure 18-6). InGermany and the United States there is increasing useVANSCAN ® Continuous Mobile Thermogram by Daedalus Enterprises, Inc.Figure 18-14 An infrared photo (thermogram) showing heat loss (red, white, and orange) around the windows,doors, roofs, and foundations of houses and stores in Plymouth, Michigan. Many homes and buildings in theUnited States and in most other countries are so full of leaks that their heat loss in cold weather and heat gainin hot weather are equivalent to having a large window-sized hole in the wall of the house.388 CHAPTER 18 Energy Efficiency and Renewable Energy