This trapped air is an insulator. It increases the window's ability to resist penetration by heat. This resistance to heat penetration is also referred to as the window's R-value. Any action taken to increase a material's R-value will decrease energy use and increase energy savings. Another option to selecting energy efficient windows is to choose a type of glass or glass treatments that can have a great effect on energy savings.
Proper installation is also significant in energy conservation.
Applying caulking to the window frame prior to placing the window in the designated area will reduce air infiltration. Similarly, a bead of caulking, or liquid styrofoam applied after the window is fastened will help insure a perfect seal. The style of window chosen will also affect the energy conservation capacity of the home. Of the common types, the casement window seems to be the most energy efficient, followed by the awning and sliding windows. Double hung windows follow with a higher leakage rate, and the least efficient window is the jalousie.