Many homes lose costly heat the old-fashioned way: through outdated windows.
"Just look at them: They're big holes in your walls!" says Lindstrom. "In Florida, it's jalousie windows. In Chicago, it's double-hung windows with the uninsulated box where the cast-iron weight travels. People lose a ton of energy this way."
Double-pane thermal windows arrest the heat transfer by inserting dead-air space, a poor conductor, between two panes. Unlike single-pane windows, which can lose more heat in winter than they let in, energy-efficient windows enable homes to take advantage of free solar heating during chilly weather.
"If we go into an old house that has single-pane, glazed, weighted windows, we can save them 30 percent right off the top, no problem," says Lindstrom. "Your return on investment could be as little as two years."
As a make-do plan, create your own energy-saving dead-air space by affixing clear plastic sheeting over the interior opening of unused windows.
Cost: Energy-efficient double-pane windows start at around $150.
Savings: A whole-house window upgrade can save 16 percent to 21 percent on annual heating costs, according to EfficientWindows.org.