Home efficiencies: What's good, what's best

Keeping your home temperate

Good option: Insulation

Cost: About $100

Installing insulation will keep your house warm in the winter and cool in the summer so your furnace and air conditioner don't have to work as hard.  

A roll of fiberglass insulation measures 6.25 inches by 15 inches by 39.2 feet and costs about $16. Eric Griffin, an energy consultant and general contractor in Macon, Ga., says he recommends hiring professionals for the project.

"They can come out, install it and provide all the materials and labor for what it would cost me to get the materials at a store," he says.

The price for this service depends on where you live. In Georgia, for example, the service generally runs between 55 cents and 65 cents per square foot for blown-in cellulose or fiberglass.

Hiring a contractor to install spray-foam insulation — considered a superior product, because it forms an air barrier that seals leaks — runs about $1.95 per square foot. As with all of these home improvements, your energy-bill savings depend on your location and climate.

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Keeping your home temperate

Best option: Passive-house retrofit

Cost: Tens of thousands of dollars

Insulation is great. But if you have the money to spend and want to be superefficient, the "passive house" movement could be your ticket.

Passive houses are so well-insulated and air-tight that heating losses are kept to a minimum. In fact, the heat generated by people, the sun and electrical appliances provide all the necessary warmth.

"A passive-house retrofit is doing conventional energy upgrades on steroids," says James Jenkins, sustainability director for BNBuilders in Seattle. That means extra-thick insulation in the attic and superhigh-efficiency windows, for example.

The biggest challenge, Jenkins says, is dealing with so-called thermal bridges, essentially highly conductive materials such as concrete that allow heat an easy escape.

Passive-house retrofits are rare in the U.S., but Tad Everhart and his family in Portland, Ore., have nearly completed one for more than $130,000 and two years of time.

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Sealing air leaks

Good: Foam and caulk

Cost: Less than $100

By far the biggest bang for your energy-efficiency buck is sealing air leaks in and around the house, from those around light switches to gaps between windows and doors. Keeping air from escaping means that you may spend less money and energy to maintain a certain temperature in your house.

"Air sealing is one of those things that people who are willing to tackle a project themselves can go and do on their own," says Stephen Pipson of Home Performance Specialists, a green consulting company in Madison, Wis. "All you've got to do is go into the hardware store and buy some foam in a can, some caulk … sometimes, it can be a piece of wood."

If you'd rather not do the work yourself and are willing to spend a little more, you can hire a general contractor to do the work for around $600, Pipson says. Even then, you'll recoup your costs in two to three years.

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Sealing air leaks

Best: Replace your windows with high-performance models

Cost: $7,000 to $20,000 for windows for an average house.

Unless it's election season, odds are the knock on the door is a window salesperson full of promise about slashed utility bills.

"(These salespeople) got the marketing down, that's for sure," Griffin says. "But I'd say 95% of the time, windows are not the high priority, unless there are extenuating circumstances."

That's because new high-performance, double-pane windows generally cost from $300 to $700 each. Costs increase an additional 15% to 20% if you need custom sizes. If you are replacing single-glazed windows, newer models may cut your utility bill by 10% to 25%.

Pipson says it can take 30 to 40 years to recoup your costs.

But if your current windows are beyond repair, go for new energy-efficient ones. Look for a low "U-factor," which measures how well a window prevents heat from escaping, Griffin says.

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Cutting electricity dependence by going solar

Good: Do-it-yourself solar-panel kit

Cost: $100 to $600

Few things show off your green credentials more ostentatiously than rooftop solar panels. But adding them can be expensive, and the payback may take at least a decade — longer than most people own a house.

"So, at least for the average homeowner, that doesn't really pencil," says Jared Silliker, a green-building consultant in Seattle.

If you are up for a project, do-it-yourself solar-power kits cost a few hundred dollars and provide panels, charge controllers, wiring and batteries. While a panel or two might not cut your energy bill by much, it can generate enough electricity to run small appliances. And you can always add on at your leisure.

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Cutting electricity dependence by going solar

Best: Complete solar-energy retrofit

Cost: $15,000 to $50,000 for an average home.

A solar-energy retrofit usually involves professionals who install and orient solar equipment that will provide 50% to 100% of your electrical needs. But with high upfront installation costs, it could take years for you to see a return on your investment.

To generate enough electricity to run an average home, you will need many solar panels. To calculate just how many, divide your daily kilowatt-hour usage — usually found on your electricity bill — by the average hours of sunlight per day in your area. Multiply that by 1,000 to convert it to watts. Once you add it up, you'll find you need quite a few of even the larger, 120-watt panels.

People who go this route tend "to be the folks who are really dedicated to the environment and want to do it because it is the right thing to do and have the money," Pipson says.

Griffin urges caution on solar retrofits. There's no point shelling out $20,000 or more for solar panels if the house is full of air leaks, is poorly insulated and contains old appliances, he says.

"I generally try to recommend to people to focus in on reducing their demand for energy as opposed to supplying themselves with more," he says.

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Keeping your home from absorbing too much heat

Good: Shade trees

Cost: As low as $10 for a sapling; a hybrid poplar is about $40

The summer sun beating through a window can heat up a home quickly. Think outside the box and plant a shade tree in the yard.

"If you can stop the sun's heat from getting to your home, that's going to save a lot of energy," Griffin says.

Deciduous trees — the ones with leaves that fall off in the winter — are especially good because they allow warm sunlight to hit the house in the cold months and provide shade in the warm months. A wall of evergreens can serve as a break against a fierce wind.

Griffin says that planting trees is a long-term strategy because it may take a while for them to grow. But saplings are relatively inexpensive, running about $10 to $40 for most common varieties, such as cherry trees and poplars. Homeowners also can spend more to have their yard landscaping done professionally.

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Keeping your home from absorbing too much heat

Best: Straw-bale-insulation retrofit

Cost: Starting around $10,000

A common building material in the U.S. between 1895 and 1940, straw bales are making a comeback as home insulation, thanks to rising costs of materials and environmental concerns, the Energy Department says.

A new straw-bale home generally costs about 20% more than a conventional home but can bring an energy savings of about 75% over the life of the home, says Andrew Morrison, who runs StrawBale.com, where he provides information on the building technique.

You can retrofit an existing home with straw bales, too, but this requires steps to keep the bales dry, such as installing extended roof overhangs.

Cadmon Whitty,who owns straw-bale construction company Paja Construction in New Mexico, wrapped his 1,000-square-foot house in straw bales — in addition to adding new windows, doors and ceiling insulation — for $12,000. He says he expects to recoup the cost in eight years.

Similar work by a contractor will cost about $100 per linear foot, Whitty says.

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Rehabbing your roof to reduce bills

Good: Cool roof

Cost: About $600 for a 1,500-square-foot roof; a gallon of metallic aluminum pigment roof paint, which covers about 50 square feet, runs $20.

The Energy Department says that in the summer, conventional, dark-colored asphalt roofs can get as much as 50 degrees hotter than reflective or light-colored roofs.

Solar reflectance is the key to keeping your house cool and reducing air-conditioning bills.

When it comes to picking a cool roof, there are many choices, from solar-reflective coatings and paints, which are relatively inexpensive, to more costly all-metal roofs that are coated with  silicone-polyester or fluoropolymer paints.

The installation and material costs for cool roofs can range from a few pennies per square foot for a coated roof to twice the cost of a conventional roof.

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Rehabbing your roof to reduce bills

Best: Green roof

Cost: Between $15 and $20 per square foot, not including the cost of reinforcing the existing structure. For a 1,500-square-foot roof, this can cost $30,000.

Green roofs can effectively cut energy use. They feature a layer of living plants on top of a waterproof membrane. The greenery acts as shade and insulation.

Typically, green roofs have several inches of topsoil, along with hardy plants. Because these roofs are heavy, retrofitting an older house involves significant structural engineering, which gets expensive. Construction costs can be as much as four times that of a conventional roof. In some cases, a green roof can cost more than $100,000.

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