Homes built today are generally twice as efficient as their 1980s counterparts. Improved window technology, more efficient heating and cooling equipment, better control of air infiltration, and greater use of insulation are helping decrease energy use in today’s homes. But building science—the physics of optimizing building performance and understanding why buildings fail—also plays a pivotal role.

Building science encompasses the study of heat transfer, airflow, and moisture movement through building enclosures; and how those factors affect the building’s performance, durability, comfort, and air quality. It predicts and measures the relationship people have to the controlled environment of buildings. Building science encompasses home design, construction, diagnostics, repair, and operation—all pitching in to make better buildings.

Dealing with Heat Flow

Insulation controls the flow of heat through a building assembly by slowing the conductive heat transfer through the envelope. Wherever floors, walls, ceilings, windows, and doors are exposed to differing inside and outside temperatures, heat conduction takes place.

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While charges of greenwashing and opportunism have been among the responses to the program’s roll-out, Jarvis told me that Eco-Options is the end result of seventeen years of work and planning by the company. "This isn’t a marketing ploy," he said. "We’ve been studying these issues, and leading the industry during this period." Jarvis described the program as "merchant-driven," and noted that Home Depot has gone to its vendors with specific requests for more environmentally-friendly products. He told me "A lot of the changes you’re seeing are driven by us." The results of this effort have included a eco-friendly green cleaning product from Terracycle, low-VOC paints from Glidden, and plantable pots for live plants, among others.

Jarvis also noted that the company has worked to reduce the environmental footprint of its stores, which led to $20 million in energy savings in 2006; the company has also built four LEED-certified stores, and four more that used LEED standards as guidelines for building.

Of course, the true test of any green retail program is its ability to help consumers make better choices for their homes and families. So, in addition to talking with us, Jarvis and the Environmental Innovation team put together the following five home improvement tips for saving energy — and money.

1. Don’t Wait to Insulate

According to the Department of Energy, up to 45 percent of a home’s energy loss is through the attic.

Upgrading insulation to a higher R-value can drastically lower energy costs. Start with insulating the attic and unheated crawl spaces with PINK Fiberglass Insulation from Owens Corning and GreenFiber Cocoon Blow-In Cellulose Insulation. It fills in gaps and voids in a home, creating a thermal blanket of protection, and the insulation reduces noise, airflow and energy loss.

Here are some tips from The Home Depot on installing insulation in the attic:

• Start at the outer edges of the attic and work toward the center.
• When adding a second layer of insulation, always use unfaced insulation, because faced insulation will add a second vapor barrier and create moisture problems.
• If the joist cavity is not full, add a second layer of insulation on top of the first to fill it up.
• Use continuous rolls in attics and floors because of longer joist spans.
• If you have to cut insulation, do so in a well-ventilated area to keep the amount of fiberglass dust raised to a minimum.
• Blown-in cellulose insulation is an alternative to fiberglass insulation, but it requires a machine to fluff the insulation and feed it through the installation hose.

2. Fill the Cracks

Air leaks raise a home’s energy bill and make a house drafty and uncomfortable in cold weather. The biggest leaks are almost always hidden in the attic or basement.

To find leaks in the attic, follow these steps:

• Look for holes along the top of a wall that leads down into the house, including those for wiring and plumbing.
• Check for insulation that is dirty around the edges, which indicates that air has passed through.
• Feel for drafts around gaps and cracks.

There are numerous places in the home where air can leak. Check all of these areas:

• Along the top of the basement wall or crawl space where the cement comes in contact with the frame
• Plumbing and dryer vents
• Recessed can lights
• Furnace flue or duct chase ways
• Indoor and outdoor electrical wires
• Window and door frames

In many cases, the best way to block air leaks is by filling the gap with caulk, expandable foam or weather stripping. Expanding spray foam like Great Stuff™ Home Sealant is ideal for sealing gaps in the attic. Spray foam should not be used next to chimneys or flues that get very hot.

3. Program Your Temperature

An Energy Star® qualified programmable thermostat, like the RiteTemp™ Seven-Day Programmable Thermostat, keeps your home comfortable and saves energy costs by automatically adjusting temperature settings while you are asleep or away.

The Home Depot suggests the following tips for installing a new thermostat:

• Turn off the power to the heating and air-conditioning system, and remove the old thermostat cover plate.
• Unscrew the thermostat mounting screws and remove the thermostat body.
• Label the low-voltage wires to identify their screw-terminal locations using masking tape. Disconnect the wires.
• Remove the old thermostat base by loosening the mounting screws. Tape the wires to the wall to prevent them from slipping into the wall cavity.
• Thread the low-voltage wires through the base of the new thermostat. Use a small level to verify accurate mounting.
• Connect the low-voltage wires to the appropriate screw terminals on the base. Follow the diagram in the new thermostat owner’s manual.
• Locate the low-voltage transformer that powers the thermostat. Tighten any loose wire connections.
• Install batteries in the thermostat body, and attach the body to the base. Restore power and program the thermostat as desired.

4. Enhance Your View

Your home’s windows may keep the outdoors from coming in, but they may not be keeping all of the air inside your house. Heat can escape from windows (such as single-pane windows) that aren’t energy efficient. Depending on where you live, you can save between $110 - $400 a year in energy costs by installing Energy Star®-qualified windows.

5. Branch Out

Plant a tree for an all-around environmental boost. When properly sited, trees and other landscaping can save up to 30 percent in home cooling and heating costs.