By carefully "deconstructing" the old rooms, rather than ripping them down, your contractor can salvage many of the parts he's removing—from plumbing fixtures to doors, radiators to cabinetry, appliances to hardware. Then, rather than putting those into the dumpster and paying to send them to a landfill, you can give them to a local Habitat for Humanity ReStore building materials recycling center, which will come and pick them up—and give you a tax deductible receipt for your donation. It's a win-win-win. You get a tax tidy write off. Your contractor gets a smaller waste-hauling bill. And other homeowners in your area get affordable building materials. Plus, everyone gets to feel just a little bit greener.

Of course, not every contractor will welcome this process, because they, too, put a premium on getting the work done as fast as possible. "Contractors don't like change, says Curt Schultz, a Realtor-architect-builder in Pasadena, Calif. "And they're used to racing to get the demo done as soon as possible with the cheapest labor possible."

But many states are forcing contractors to change their ways. "We now have to fill out forms accounting for everything we put in the dumpster," says Woodcliff Lake, N.J. design-build contractor Rob Wennersten. "Certain items have to go to the recycling transfer station, so the more that gets donated, the simpler the process becomes." Other localities, such as Los Angeles County, make proof of recycling part of the building permit process, says Schultz. "If the change hasn't happened in your area yet," he says, "it will be happening soon."

Talk to your prospective contractors about their approach to salvaging reusable parts during demolition to gauge their willingness—and to put them on the record about what they're going to do.

Architectural salvage centers like Habitat for Humanity ReStore typically look for these:

• Appliances in perfect working condition and no more than 10 years old
• Cabinets that are complete (meaning the entire box plus doors and drawers) and have no water damage
• Doors with no rot, broken glass or peeling paint
• Windows must be double-paned and whole (with the frame intact)
• Lighting in good working order
• Plumbing fixtures must contain no rust or other significant damage
• Almost any woodwork, such as mantels, columns and leaded glass windows, as long as they're complete
• Large remnants of new flooring
• Hardware such as doorknobs in complete sets