It is important to note which exact features make a window or door energy efficient, since they directly impact the energy consumption of the house, heating costs and the environmental impact. Windows are considered to be energy efficient when the frame is made of high-quality material such as 100% extruded vinyl, when the glass is made of multiple panes filled with insulation gas such as Argon, when Super Spacer technology is present, and the glass is coated with Low E or Low E 2 coating which reflects the heat. Doors are considered to be energy-efficient when the core of the door is insulated with foam, the composition material is solid, the frame is a tighter fit to the spacing, and multi layered weather stripping is used.