Radiation:The transfer of energy or heat in the form of electromagnetic waves from one surface to another.
Rail:Horizontal member of a window sash or door panel.
.Retrofitting: Adding or replacing items on existing buildings structure.
Reflective Glass: Window glass coated to reflect radiation striking the surface of the glass.
Replacement window: is a window that is installed in an existing window opening.
Rough opening: The opening in a wall where a window or door will be installed.
Round Top: A true half round with extended legs.
R-Value: A measure of resistance to heat flow. A high-R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value.