A number of window attributes, starting with the manufacture of the window product, contribute to the energy efficiency of the window. Most windows in today’s market have insulated (or double-paned) glass which is a basic component to better insulation and higher energy efficiency. Other common features applied in the industry to increase energy efficiency are “Low E” coatings on the glass and “Argon Gas” fill between the panes of glass. Big name warehouse stores many times offer an inexpensive off-the-shelf window. Often times, these inexpensive “cheap” windows are not energy efficient. The United States Department of Energy has established “Energy Star” guidelines that products should meet to be considered energy efficient. Ask your window dealer if the window meets the Energy Star standards.