IF YOU DON'T HAVE THE MEANS (or desire) to build a green dream home from scratch, there's still plenty you can do to turn that inefficient 1950s split-level or drafty, er, classic Victorian into a model of 21st-century sustainable living. As anyone who's ventured into a home-improvement warehouse knows, the sky's the limit when it comes to cost. So Sierra offers you a range of options, from simple to sophisticated, that can help reduce your abode's ecological footprint. Every step matters--and the easiest ones are often the most cost-effective.

Space Heating | Water Heating | Cooling | Insulation | Appliances |
Sustainable Materials

SPACE HEATING

Simple Fix CHANGE YOUR FURNACE'S AIR FILTER EVERY ONE TO THREE MONTHS. You can do this easy step yourself. A clean filter allows your heating system to work more efficiently, which saves energy and extends the life of your furnace.

More Sophisticated INSTALL A PROGRAMMABLE THERMOSTAT. Having a thermostat that automatically turns the heat down while you're asleep or away from home significantly reduces energy use. Setting the temperature to 65 degrees Fahrenheit during the day and 60 degrees overnight, for example, can cut energy consumption by 10 percent. You'll probably recover the cost of the programmable thermostat in the first year. For more information, visit the U.S. Department of Energy's Energy Efficiency and Renewable Energy Web site and search for "programmable thermostat."

SEAL YOUR DUCTS. Homes with forced-air heating systems commonly lose 20 to 40 percent of their heat through poorly sealed duct joints. Some states offer tax credits for duct work done by a qualified contractor. For duct-sealing and other insulation tips, go to the Energy Star Web site and search for "ducts."

Whole Hog REPLACE YOUR OLD FURNACE WITH A HIGH-EFFICIENCY MODEL. If your furnace was purchased before 1978, it probably burns about twice as much fuel as necessary. Installing a modern gas furnace, which can achieve up to 97 percent efficiency, will slash your natural-gas consumption nearly in half. For details, read the American Council for an Energy-Efficient Economy's online consumer guide.

LET THE SUN IN. Even in cold climates, homes can be weaned off fossil fuels with a remodel that integrates passive solar techniques. A sunroom, double-paned south-facing windows, and overhangs can create a bright, efficient abode. The Northeast Sustainable Energy Association provides good resources at nesea.org/buildings/passive.

WATER HEATING

Simple Fix BUNDLE UP YOUR WATER HEATER. If your water heater's storage tank is warm to the touch, it's wasting energy. For under $20, you can buy a precut jacket for the tank that will reduce energy loss by as much as 45 percent. For details, go to www.eere.energy.gov/consumer and search for "water heater tank."

More Sophisticated GO TANKLESS. A typical storage water heater, even with a blanket, wastes about 15 percent of its energy through heat loss. A tankless, or "on-demand," water heater uses energy to heat water only when needed. State and federal tax credits and incentives keep the cost of purchasing a tankless water heater relatively low. The Gas Appliance Manufacturers Association Web site offers up-to-date comparisons of models and details on federal tax credits in the "Product Directories" section (under "Product Certification").

Whole Hog HARNESS THE SUN. A solar hot-water system can supply 60 percent of the energy a family of four needs to heat its water. Install photovoltaic panels to provide power with a passive solar collector or a tankless water heater, and you've got one elegant way to heat your bathwater. The estimated payback period for a family-size system ($3,000 to $6,000) is 10 to 20 years, but it should be shorter when you factor in tax credits and incentives and the inevitable future increases in power costs. For more information, see builditsolar.com, a comprehensive Web site that explains projects step-by-step for the do-it-yourselfer.

COOLING

Simple Fix PLANT LEAFY THINGS. Mature trees and tall shrubs around your house can lower air-conditioning costs by up to 40 percent. Deciduous trees planted to shade a house's west side--which is baked by afternoon sun in summer--have the biggest impact yet let the sun in during the winter. Go to www.eere.energy.gov/consumer and search for "passive solar home."

More Sophisticated INSTALL AWNINGS. Awnings on south-facing windows block up to 65 percent of the summer sun's heat. For this and other passive solar cooling solutions from the Department of Energy's Building Technologies Program, visit www.eere.energy.gov/buildings/info/homes and click on "Solar."

FAN AWAY THE HEAT. A whole-house cooling fan is an excellent energy-efficient choice. Using just one-tenth of the electricity of an air-conditioning unit, a fan moves volumes of hot air away from upper floors while drawing cool air up from below. By installing a solar attic fan, you can tap the sun's energy to expel the hot summer air trapped below your roof. For information on how to choose the right fans for your house, go to www.fypower.org/res and click on "Product Guides."

Whole Hog TRY A SWAMP COOLER. In a hot, dry climate, an evaporative, or "swamp," cooler provides excellent whole-house cooling. By using evaporation rather than refrigerants to chill the air, swamp coolers consume up to 75 percent less electricity than air conditioners. Some new models even run on solar power. For details, go to www.eere.energy.gov/consumer and search for "evaporative cooler."

CHOOSE A "GREEN" AIR CONDITIONER. If you live in a high-humidity area, where swamp coolers aren't effective, choose the most energy-efficient central or room air conditioner you can afford. The energy savings from a better model not only benefit the environment but also quickly repay the higher up-front costs. Check out energystar.gov (click on "Heat & Cool Efficiently," then "Air Conditioning, Central" or "Room") or aceee.org/consumerguide.

INSULATION

Simple Fix REPLACE WORN WEATHER STRIPPING ON WINDOWS AND DOORS. One of the cheapest, lowest-tech options, installing new weather stripping can save you as much as 10 percent of your winter heating costs. For instructions, visit www.eere.energy.gov/consumer and search for "air sealing."

More Sophisticated INSULATE YOUR ATTIC. Heating and cooling account for about half of your home's energy consumption. Blown-in cellulose and fiberglass insulation are usually less expensive options, but cotton batting made of recycled denim can make future access to insulated areas easier. Also available is fiberglass insulation that contains recycled glass. Go to greenhomeguide.com and click on "Energy Efficiency" in the "Know How" section.

INSULATE YOUR WALLS WITH SPRAY-IN CELLULOSE. In a total renovation in which wall surfaces are removed down to the studs, consider using spray-in cellulose, a highly effective insulation made of recycled newspaper. Spray insulation reduces air infiltration by completely filling wall cavities. Your home will be up to 40 percent more energy efficient than it would with fiberglass insulation--and quieter too. See www.eere.energy.gov/consumer/your_home.

APPLIANCES

Simple Fix GET RID OF VAMPIRE APPLIANCES. Alan Meier, a scientist at Lawrence Berkeley National Laboratory, estimates that standby power consumption accounts for about 5 percent of total U.S. residential electricity use. The wasted energy is equivalent to the output of 18 power stations. Do your part by plugging appliances into a power strip and turning the strip off when they're not in use.

More Sophisticated CHOOSE ENERGY STAR-RATED APPLIANCES. According to the EPA, in 2005 alone Energy Star appliances helped Americans avoid greenhouse-gas emissions equivalent to the output of 23 million automobiles and save $12 billion on their energy bills. Go to energystar.gov and click on "Appliances."

Whole Hog BUY A SUPEREFFICIENT REFRIGERATOR. While Energy Star fridges must be at least 15 percent more energy thrifty than federal standards, some high achievers save even more juice. Visit energystar.gov and select "Refrigerators & Freezers" under "Appliances."

SUSTAINABLE MATERIALS

Simple Fix PAINT IT AGAIN, SAM. Each year the average U.S. household stockpiles one to three gallons of old paint, hazardous waste that should never go in the trash. Several paint companies (including industry leaders Dunn-Edwards and Kelly-Moore) sell an array of latex paints recycled from just such residential leftovers. Approximately 50 percent cheaper than new paint, recycled paints are priced right--and many of them meet the Master Painters Institute's performance standards. For more information, check out the California Integrated Waste Management Board's guidelines.

More Sophisticated ENJOY YOUR DECK--AND OUR FORESTS. Reduce logging pressure on the pine and redwood forests you love by using composite, or recycled content, decking. Reclaimed wood fibers or rice hulls are combined with recycled resins to form composite boards that take screws and nails just like wood but last longer and don't require toxic stains. All-plastic decking is even tougher than composite and provides a good use for recycled plastics, but it looks less natural. To read more, go to thisoldhouse.com, click on "Exteriors" (in the "Homeowner Know-How" section), and search for "decking."

Whole Hog TREAD GENTLY. If you prefer that your hardwoods remain upright, you'll welcome the renewable flooring alternatives now available. Bamboo matures in three to five years and comes in a spectrum of shades from light to dark caramel. Cork can be harvested without harming the tree itself. Salvaged wood can be higher quality than new, since it often came from old-growth trees. Natural linoleum contains wood flour, pine rosin, and linseed oil instead of toxic chemicals and solvents. And kirei flooring is made from sorghum stalks, which are doubly green: They grow quickly and are an agricultural byproduct. Go to greenhomeguide.com and search for "green flooring materials."

Photos, from top: Courtesy of Bonded Logic Inc., Susan Heller, Danielle Johnson; used with permission.