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Making Older Homes More Energy Efficient

Old homes are valued for their solid construction and architectural significance, especially in New England. But, unfortunately, energy efficiency was not a priority at the time of their construction. Improving the energy efficiency of old homes while preserving their character and is a challenge, but not an impossible one.

First, do no harm

For older, historic homes, Sally Zimmerman of Historic New England recommends basic energy interventions and avoiding more radical or permanent changes that may subject a historic home to a high level of experimentation. The components of a 100-year-old house comprise a system that has worked together for a century. Making a drastic or irreversible change to one part of the system may result in unintended consequences.

For example, wall insulation in an old Greek Revival house (pictured) was absorbing so much moisture that the entire framing structure of the house could be read in the mildew patterns on the outside walls. These days, blown-in or dense-pack wall insulation done properly does not result in this kind of moisture problem, but, at the time of its installation, this technique may have been cutting-edge, unproven technology, or may have been poorly executed. It was likely an expensive project that ultimately compromised the structural integrity of the house as well as worsening the environment quality for the occupants.

Photo courtesy of Historic New England

Photo courtesy of Historic New England

Sally recommends treating old homes gently, taking care with wall insulation, making sure improvements are simple and reversible, and avoiding overly costly and complex projects. The total effect of many small energy improvement projects can be significant in improving an older home’s energy performance. “Old houses aren’t the best places to experiment with cutting-edge green technologies or materials. At least for old houses, being an early adopter is not necessarily the wisest course,” she said. “First, do no harm.”

What is a “historic” house?

The National Register of Historic Places specifies that historic properties must be at least 50 years old. “Our existing housing stock gives our communities and neighborhoods a distinctive character that is worth preserving and adds value, both cultural and economic, to our cities and towns,” said Sally. “In the Northeast, we have a higher percentage of pre-1920 houses than anywhere else in the country.” It’s best to minimize any losses of embodied energy and historic fabric when making changes to a historic home.

What is embodied energy? It is the “sunk” costs of material and labor that preservation economist Donovan Rypkema defines as “the total expenditure of energy involved in the creation of the building and its constituent materials.” It is energy to harvest, manufacture, modify, transport, and assemble the structure—a cost that has already been paid. We are being environmentally responsible when we maximize the useful life of the house that resulted from that expenditure.

Identify major problem areas

A good place to start when improving your home’s energy performance is determining how it falls on the Home Energy Rating System (HERS) index and setting a goal. The energy conservation standard for new homes is 100 on the HERS scale, the score for Energy Star New Homes is below 85, and the average home has a score of about 130. To begin finding out how efficient your home is, you can start with a free energy assessment. This will search your house for areas of energy loss, look at the building envelope, check mechanical systems, and look at the efficiency of the appliances. It will bring up possible actions you can take to improve your home’s efficiency and might indicate whether there are any grants, rebates, or tax returns that could facilitate the process.

If your home is eligible for subsidies for weatherization and you opt to have air sealing done, Mass Save will offer free diagnostic testing using a blower door and infrared camera to determine how fast air flows through the house (measured in cubic feet per minute). With a good diagnosis of the major energy inefficiencies, you can begin to improve them.

Small air leaks that are easy to reach can be inexpensively fixed with caulk. Windows can be tightened up with weather stripping and by using sash locks to close and seal the window tightly. If windows are a large source of energy loss, but you don’t want to replace them for historic reasons or otherwise, storm windows are an option. Storm windows can be installed on the inside or outside of a window, creating an air barrier between your home and the outdoors.

Other priority areas to reduce air infiltration, according to the U.S. Environmental Protection Agency (EPA), include bypasses, the attic floor, crawl spaces, around the attic hatch, electrical and gas service entrances, cable TV and phone line service entrances, window AC units, mail chutes, electric outlets, and around door and window frames. The EPA website offers a how-to guide on sealing and insulation.

Adding insulation to the attic is one of the most cost-effective measures to make your home more energy efficient. Other, simple measures include using shutters or door sweeps to seal up cracks where drafts can come through. Replacing the home’s heating system is another option that can be expensive, but may be eligible for incentives, including zero-interest loans and rebates.

—Kelly Gallagher

Based on the workshop “Energy Retrofits for Older Houses,” held February 28, 2015.