Energy is saved by using more efficient appliances, high performance windows, controlled air infiltration, upgraded heating and air condition systems as outlined by the Environmental Protection Agency.
Just walking through the homes, prospective buyers should notice a difference in air flow as each supply line should deliver the same amount of air to each room. Additionally, each room should be about the same temperature, otherwise it will cost more to maintain the temperature.
For new home construction, builders can join in the Energy Star effort on a voluntary basis. If they do, they must meet guidelines set forth by the EPA. These guidelines are confirmed through an inspection performed by a certified Home Energy Rater. Hernandez said the raters are hired by the builders and usually receive a certificate if the home meets the Energy Star criteria.
http://www.delmarvanow.com/bethanybeach/stories/20051012/2211211.html(EDIT: There's even an online calculator, BTW, at
http://www.energystar.gov)