Tips to Make Old Houses Energy Efficient

This historic-homes expert shares her tips for making old houses energy efficient.

No matter how much you love old houses, you’re never going to make your early Cape into a net-zero house. But it doesn’t have to be a total energy drain, either. Just ask Sally Zimmerman, senior manager of preservation services for Historic New England in Waltham, Massa­chusetts. At Historic New England, whose 36 properties include several 17th- and 18-century homes, it’s her job to help make sure those buildings are viable 21st-century structures. “It’s possible to make these homes more efficient,” Zimmerman says. “That’s what will keep them going. They’ve evolved in the past, and they’ll evolve again.”

Cap It, Trap It

Because heat rises, a poorly insulated attic can account for significant lost dollars. Start by sealing the air leaks. If there’s old fiberglass insulation, peel it back. Is it dirty? That means that air and heat are escaping. Fill in the cracks with canned spray-foam insulation. Then fill the bays between the floor joists with dense-pack insulation. “It’s the best way to go,” Zimmerman advises. “You can really stuff those cavities, and it’s reversible should it get wet.” Just be sure that your electrician takes out any compromised or old (knob-and-tube) wiring first.

Lock ‘Em Down

It may sound like such an obvious thing to do, but Zimmerman says that many people simply don’t use the sash locks on their windows—and that can result in a surprising amount of heat loss. “They actually have a role,” she notes. “They’re not just for preventing people from opening your windows when you’re away on vacation. They make the upper and lower sections a tight, single unit.” Zimmerman suggests going an extra step: Move the existing lock to one side of the window and add a second one to the opposite end to further button it up.

Go Inside

Making your old house more efficient and keeping those single-pane antique windows aren’t mutually exclusive options. In fact, the old windows are preferable. “New windows aren’t that effective, because old houses are often out of plumb and they won’t fit as well as old ones,” Zimmerman says. “And the wood in those new windows just isn’t as durable.” Instead, weather-strip the originals, and then for added efficiency, install interior storms, which Historic New England has done at several of its properties. They can be just as much of a cost saver, maybe even better, than exterior ones, with the added benefit of preserving the home’s outside look.

Control Those Temps

“It’s human nature to forget to turn down the thermostat,” Zimmerman says, but a programmable thermostat can override DNA. A good one runs about $100 and keeps your house warm when you’re there and your heat running only intermittently when you’re not.

Wrap It, Save It

If your basement is comfortably warm, then heat is probably coming off your ducts and pipes. That’s heat that should be going into the home’s living areas. Reduce the loss, Zimmerman advises, by wrapping ducts in foil-back flexible insulation. Quarter-inch-thick rigid foam also works. And wrap pipes in foam sleeves. The savings, she says, will be noticeable: “The goal is to keep the heat in the part of the house where you live.”