Virtually all competent auditors will want to perform blower–door test. The test uses a huge fan placed in an exterior door and super–sensitive measuring equipment to analyze home airflow and identify air leaks—even places you might never think to look. For example, behind built—ins, in the joint where the floor meets the walls, or in gaps created by recessed lighting or wall plates. An infrared camera can spot "cold joints". A cold joint is a term used to describe where air passes through insulation. Another test looks for duct leaks, and works much like the blower—door machine to determine duct air tightness. Energy auditors also evaluate a year's worth of energy bills to identify easy lifestyle changes you can make to lower your heating costs. They'll inspect all your appliances, HVAC, boiler, oil burner, and water heater to see whether replacements are warranted.

Typical findings may shock you almost as much as the simple methods by which those energy—draining issues in your home are solved. "Leaky light cans—some builders call them pot lights—are one of the most typical observations I make," says Michael Broussard, a certified energy auditor and owner of Home Performance Solutions LLC, an independent energy audit company in Colorado. Air–tight light—can trim kits stop air transfers between rafters and rooms, and run about $17 a piece. Remarkably, says Broussard, light cans accounted for a whopping 10% of all the air leaking from one house he evaluated. He says his audits typically save 12 to 20 percent in home heating and cooling costs for his customers. In another home, he found that the owner's blown fiberglass insulation was allowing 30% more air infiltration than would blown cellulose. "Blown–fiberglass insulation tends to be very leaky." Broussard says he often warns homeowners to be wary of replacing windows. There usually are other, simpler measures that improve window efficiency. Caulking around windows or tinting the glass will help.

Sometimes, homeowners need to look outside for tamer temperatures inside. "In Colorado we get some pretty strong winds, so I might recommend planting trees on a particular side of the house to block the house from those cold winds," says Broussard. When it comes to homeownership and energy efficiency, there are always improvements that can be made. The trick is to know which ones are right for you. "A house isn't like a car, where you can't really improve its efficiency. You can always improve the efficiency of your home. You just need to know where to look," says Broussard.

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