Homeowners who want to get the most out of their energy dollars have only to focus on two areas of the home. Unfortunately, they’re big areas.

“The main problem with most homes is the envelope,” says Corbett Lunsford, of Green Dream Group, a home performance analysis firm in Chicago, which offers energy auditing services.

The “envelope” is just what it sounds like – the shell of the house that if properly sealed, can keep your hot and cold air where you want it. The heating, ventilation and cooling system (HVAC) controls the temperature.

Lunsford uses scientific testing to tell homeowners exactly where their homes are losing energy and then offers advice on the best steps to make them more efficient.

A common issue, he says, is homeowners who try to make improvements on their own without first having an energy audit done by a professional who is certified as such by the Building Performance Institute (BPI) or is a certified Home Energy Rater (HERS) by the Residential Energy Services Network (RESNET).

“A contractor that really checks their work would first do a blower door test before they start anything,” Lunsford said. “That’s the main test for home performance. It tests the air tightness in the house.”

Lunsford said he often gets calls from homeowners who have already spent thousands of dollars insulating their homes or upgrading their windows, only to still be dissatisfied with their comfort level and/or energy bills.

Homeowners should first air seal the attic, then air seal the basement or lowest level of the house before addressing windows, doors or the middle floors of the home, he said.

“Windows do not make a big difference in homes where there are envelope and HVAC problems,” Lunsford said. “Once you’ve (addressed) the envelope and HVAC systems, then windows can make a big difference. The most common mistake people make is prescribing their own solutions for things.

“Most people think they need to insulate their attic, but that’s not (entirely) the case. If you insulate the attic without air sealing it, you’re actually wasting thousands of dollars. Air sealing is the No. 1 secret almost no one understands. It’s the main opportunity for improvement in every house, period.

“I see people wasting thousands of dollars every single year. It gets me really annoyed because it’s so easily solvable.”

Additional insulation is only as good as the person doing the insulation, added Buddy Edwards, of AC Lynn Homes in Charlotte, which focuses on green building and remodeling.

“We highly encourage all of our customers to put their money (towards insulating the home) first,” Edwards said. “That’s where they’re going to get the most bang for their buck when it comes to home performance and energy efficiency.

“It can be as simple as just installing a traditional batt insulation product properly.”

Homeowners who are interested in making energy efficient improvements should meet with a designer and contractor who have the expertise and training to meet the homeowner’s needs and desires.

“What we like to do is team up with bringing the designer to the table and sit down and talk about everything (regarding) the homeowner’s lifestyle, interests and needs over the next five years and how that changes over time,” Edwards said. “We’ll look at budgets to make sure all those sorts of things are being considered when the projects are being designed.”

Angie Hicks is the founder of Angie’s List, a resource for local consumer reviews on everything from home repair to health care.