GLOSSARY-R

Radiation

The transmission of energy through space without heating the air between, as in Solar Radiation.

Rail

The horizontal members of a window sash or door panel.

Reflective glass

Window or door glass coated to reflect radiation striking the surface of the glass.

Rough opening

The opening left in a frame wall to receive a window or door unit.

Rough sill

The horizontal rough framing member, usually two inches by four inches, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and is supported by cripples.

R-Value (Thermal resistance)

A measure of resistance to heat flow of a material or construction; a higher value indicates a better heat insulating property. The R-value of an ordinary single-pane sash with a 15 mph wind on one side is about 0.9.