GLOSSARY OF WINDOW TERMS The Learning Center 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. Relative Heat Gain (RHG) A calculated relationship of heat gain (through a window system) that accounts for center-of-glass U-value and center-of-glass shading coefficient based on a standard inside and outside temperature. R-Value (also R-Factor) A measure of a product's ability to resist the transfer of thermal energy. The inverse of U-factor (R=1/U), R-value is expressed in units of hr-sq. ft -ºF/Btu. A high R-value window has greater resistance to heat-flow and a higher insulating value than one with a low R-value. Sash  This is the term for the part that holds the window. For example, in a double hung window there is a top window (sash) and a bottom. Rough Sill - Sealant Sash Lock Generally, a cam-action type lock applied to the check rails of a sliding window or at the open edges of a projecting window to pull the check rails tightly together or to seal the sash tightly to the frame, both for security and weather-tightness. Sash Weights In older double-hung windows, the concealed cast-iron weights that are used to counterbalance the sash. Sealant A substance, which adheres to the glass and the spacer, sealing an insulated unit. It must provide adhesiveness and a minimum of moisture transmission through itself. When one substance provides both these characteristics adequately, the unit is called a single-seal unit. Sometimes two materials are needed for the desired result, which makes a dual-seal unit. < previous main menu       next > 3245 Miracle Drive Murrysville, PA 15668 724-387-2991 PA Contractor ID PA001856