A cold January night last week was a fitting time for energy engineer Mark Kelley to pass along some professional wisdom as he answered homeowners’ questions in a Home Energy Q & A Night sponsored by Harvard Local at the library’s Volunteers Hall.
Kelley’s first words gave a clue to the relaxed and easy tenor of the evening.
“I just finished work today at 5 p.m.,” Kelly said. “I really just finished—the last piece of work for my last client.”
“Last” for at least six months, anyway. After almost four decades of working in energy engineering, during which he has become a leader in green building, one of the forces behind the Energy Star program, and the president of Hickory Consortium, Kelley is starting a long-planned sabbatical, but not before offering some practical advice for homeowners.
Kelley emphasized the importance of first attending to the basics: sealing the housing envelope to reduce air leaks and then adequately insulating to retain heat.
To assess air leakage, Kelley suggests getting a blower door test that tests the tightness of the housing envelope by measuring the pressure differential inside and outside the house while a strong fan blows air out. Look for leaks, especially around windows, doors, basement sills, and attic openings. Pay particular attention to uninsulated ducts traveling through unheated spaces.
Next, Kelley recommended adding insulation.
“Whatever you have probably isn’t enough,” he said.
Insulation standards from the 1960s to 1990s were based on the insulation cost efficiency relative to the price of oil. With increasing concerns about the price of oil, environmental impact, and climate change concerns, there are now more than dollars-and-cents reasons to increase insulation.
Among solar alternatives, Kelley ranked passive solar—sunspaces, daylighting, and thermal mass, for example—as the most efficient. Active solar systems and solar hot water have short payback periods, while solar electricity is the most costly and least efficient. Before investing in solar electricity from photovoltaic panels, Kelley recommended first putting money into insulation. According to Kelley, solar electricity costs about $0.29 per kilowatt compared to grid electricity at $0.15. From the audience, Marilyn Strong pointed out that the true cost of heavily subsidized fossil fuels is hidden, making alternative solutions appear more costly in comparison.
Surprising to many, Kelley upended the conventional wisdom of ventilating attic space to prevent ice dams when he said that the building science community is turning to “hot roofs,” roofs fully insulated and without attic ventilation in the winter. He suggested spraying urethane foam on the underside of the roof and using removable Styrofoam covers on end vents in the winter.
Moving from the attic to the basement, Kelley said to insulate basement walls rather than the basement ceiling. For older homes, he cautioned not to insulate more than two feet below grade to prevent influencing the outside ground temperature downward and possibly affecting the existing foundation.
For old homes with stone basements, Kelley said that other than encasing them behind a glass wall, a homeowner may have to choose between seeing the stones from a cold basement and spraying them with foam insulation.
Windows represent a high heat loss per square foot, but Kelley did not recommend rushing to replace existing double-pane windows. Rather than replace single-pane windows in an historic house, Kelley suggested considering tight storm windows. He also recommended honeycomb-style window shades made from a nonporous material as effective against heat loss if they are installed with little air space on the sides.