Practical Preservation: Energy Efficiency in the Old House

warner mansionHave you ever noticed the belvedere on top of the historic Governor Warner Mansion? The second floor stairway that seems to lead nowhere actually leads to a hatch door and then up into that tiny, boxlike room. In the summer, the hatch and the belvedere windows can be opened to draw hot air up and out of the house.

Old houses were built with many such features to maximize energy efficiency. Granted, early-20th-century cooling strategies—such as belvederes, operable windows, and strategically-placed doors to allow air flow—might not live up to our current standards for comfort. However, many other features do.

And these energy efficiency measures can help lower utility bills for any house, whether it is 100 years old, 10 years old, or somewhere in between.

Get an Energy Audit

Hiring an energy audit contractor is a good start for a comprehensive energy efficiency project. An energy audit will last two to three hours and cost a few hundred dollars, but is well worth the investment.

thermographic image

Both Consumers Energy and DTE have approved contractor lists on their websites, and offer a number of rebates associated with energy efficiency projects such as furnace tune-ups, air leak sealing, and insulation.

During an energy audit, the contractor will ask about your energy usage patterns and examine your utility bills, usually a year’s worth. He or she will also perform several tests to locate where your house is losing air, and where it’s infiltrating from outdoors.

This work might include blower door tests, infrared camera testing, and furnace testing (such as duct pressure tests and flow hood tests).

Seal Air Leaks

When it comes to costly utility bills, air leaks and poor insulation are the two most common culprits. Any point on the exterior of your house where an interior system exits can be a source of heat loss—like chimney flues, dryer vents, and telephone, cable, electrical, and gas lines.

incense stick

There’s a simple DIY test for air leaks: On a windy day, light an incense stick and hold it in front of each opening on the indoor side of the exterior wall. Look for drifting smoke to identify leaks.

Most small openings, once found, can be filled with silicone caulk.

If you have a fireplace, close the damper when it’s not in use. During the spring and summer, a metal fireplace insert can help prevent cool air from vanishing up the chimney.

On the interior of your home, if you have a fireplace, always close the damper when your fireplace is not in use. During the spring and summer, use a metal fireplace insert for additional air loss prevention. Check all exposed ductwork for breaks and gaps, and seal with heat-proof tape where needed.


Most houses built prior to 1940 were made with little to no insulation. A poorly insulated attic, as well as an attic hatch door, is often the greatest source of heat loss in a home. To counteract this, either batt or loose fill insulation can be put between joists to insulate an attic space. Cellulose, although most expensive, is most effective. For attic doors, add rigid insulation and weather-stripping to the back.

When selecting insulation, avoid urea-formaldehyde foam or cellulose treated with sulfates. Mixed with water, sulfates create sulfuric acid, which corrodes metal. Instead, choose insulation treated with boric acid, a fire retardant.

While you are in your attic, remember to check exposed ductwork for breaks and gaps, and seal with heat-proof tape where needed. You might also consider foam tube insulation for ductwork and pipes. It keeps your water hot and also helps prevent frozen pipes—plus, it’s inexpensive and easy to use.

siding insulation

Wall insulation on an old house is rarely effective as an energy efficiency measure. Not only can it be costly to install, it also ruins some of the building’s original features in the process.

If it’s absolutely necessary to insulate the exterior walls, keep the damage to a minimum by drilling small fill holes either in or under the exterior siding, or drilling small, inconspicuous fill holes in interior walls.

If you’re concerned about moisture insulation, rather than heat, a vapor barrier can be easily created on the interior wall by using impermeable paint.

Finally, remember that where you have insulation, you must have ventilation. Make sure your roof has gable, soffit, or ridge vents. For exterior walls, siding can be lapped to allow ventilation, or concealed vents can be placed in interior walls.

Look at our resources page for more helpful links, and our workshops page for information on the energy efficiency workshop, to be held in late summer.

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