Obscure Glass - Any textured glass (frosted, etched, fluted, ground, etc.) used for privacy, light diffusion, or decorative effects.

Operable Window - Window that can be opened for ventilation.

Operator (Crank) - Operated device for opening and closing casement or jalousie windows.

Oriel Window - A window with unequal sash.

OSHA - Occupational Safety and Health Administration is a federal agency charged with making the laws and standards that are designed to make the workplace safe.

Palladian Window - A large, arch-top window flanked by smaller windows on each side.

Pane - One of the compartments of a door or window consisting of a single sheet of glass in a frame; Also, a Sheet of Glass.

Panel - A major component of a sliding glass door, consisting of a light of glass in a frame installed within the main (or outer) frame of the door. A panel may be sliding or fixed.

Panning - In replacement window work, the outside aluminum trim that can extend around the perimeter of the window opening; used to cover up the old window material. Panning can be installed in the opening before the window, or attached directly to the window before installation.

Parting Stop - A narrow strip, either integral or applied, that holds a sash or panel in position in a frame.

Passive Solar - A solar heating system that operates on natural thermal processes, and uses no external mechanical power to move the collected heat. Generally, the building's structure itself forms the solar system.

Patio Doors - Sliding glass doors, often used for access to a deck or terrace.

Peak Load - The maximum thermal load to be provided by a heating or cooling system in a house.

Photochromics - Glazing with the optical properties that change in response to the amount of incident light.

Picture Window - A large, fixed window framed so that it is usually, but not always, longer horizontally than vertically to provide a panoramic view.

Pivot Window - A window with a sash that swings open or shut by revolving on pivots at either side of the sash or at top and bottom.

Plate Glass - A rolled, ground, and polished product with true flat parallel plane surfaces, affording excellent vision. It has been replaced by Float Glass.

Plumb - The condition of exact vertical alignment.

Polyurethane - Product produced by the reaction of a polyfunctional isocyanate with a polyol or other reactant containing two or more hydroxyl groups.

Polyvinylchloride (PVC) - An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.

Poured and Debridged - Framing system thermal break made by flowing a catalyzed liquid material with low thermal conductivity into a one-piece channel and then removing the base of the channel or bridge after solidification to form a thermally improved extrusion. Also see Thermal Cavity.

Primer - A substance that improves the adhesion of sealant or paint.

Projected Window - A window fitted with one or more sashes opening on pivoted arms or hinges. Refers to casements, awnings, and hoppers.

PSF (Pounds Per Square Foot) - A measurement of air pressure used in window testing, e.g., 1.56 psf (25 mph) or 6.24 psf (50 mph).

Pull Hardware - A fixed handle or grip used to pull a door open.

Punch - To perforate by pressing a non-rotating tool through the work.

Purlins - Horizontal members extending between rafters for supporting the glass on slope-glazed systems.

Pyrolytic Coating - A special coating sprayed directly onto glass while it is still in a molten state, resulting in a permanently embedded surface coating. Sometimes referred to as hard-coat low-E.

R-Value - A measure of the resistance of a glazing material or fenestration assembly to heat flow. It is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-°F/Btu. A high R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value.

Racking - The forcing out-of-plumb of structural components.

Radiation - The transfer of heat in the form of electromagnetic waves from one separate surface to another. Energy from the sun reaches the earth by radiation.

Rafter - For sloped glazing, a main nominally sloped framing member.

Rail - A horizontal member located at the top and bottom of a window or door.

Ream - To finish a drilled or punched hole very accurately with a rotating fluted tool of the required diameter.

Receptor - A channel-shaped, telescopic member which adapts the frame of a window wall or storefront system to the size of the window wall or storefront system opening; an adapter.

Reflectance - The ratio of reflected radiant energy to incident radiant energy.

Reflected Radiation - Solar radiation that strikes an exposed surface (like a window) after being reflected from the ground, trees, buildings, snow, etc. Reflected radiation can provide a significant amount of heat when vertical windows are used.

Reflective Glass - Window glass coated to reflect radiation striking the surface of the glass.

Refraction - The deflection of a light ray from a straight path passes at an oblique angle from one medium (such as air) to another (such as glass).

Relative Heat Gain - A measurement of the total heat gain through glazing for a specific set of conditions.

Relative Humidity - The percentage of moisture in the air in relationship to the amount of moisture the air could hold at that given temperature. At 100 percent relative humidity, moisture condenses and falls as rain.

Resfen - A computer program used to calculate energy use based on window selection in residential buildings.

Retrofit - To add new materials or equipment not provided at the time of original construction.

Reveal - In windows it is typically the distance from the glazing to the edge of the frame. On hinged doors it is the distance from the face of a door to the face of the frame on the pivot or hinge side.

Ridge - The horizontal member at the junction of the upper edges of two sloping glass areas.

Roof Window - A fixed or operable window similar to a skylight placed in the sloping surface of a roof.

Rough Opening - The opening in a wall into which a door or window is to be installed.

Rough Sill - The horizontal rough framing member that forms the bottom of the rough opening.

S -Value - Section Modulus of the cross section of a member about the neutral axis perpendicular to the loads. This section property is used to calculate the stress on a member under loads. It is directly proportional to the capacity of the member. (Higher S-values improve the member’s performance and reduce internal stress.)

S.T.C. - Sound Transmission Class is a single number rating that measures the sound insulation value of a partition, door, or window. It is derived from a curve of its insulation value as a function of frequency. The higher the number, the more effective the sound insulation.

S.T.L. - Sound Transmission Loss is a measure of the sound-insulation value of a partition. It is the amount, in decibels, by which the intensity of the sound is reduced in transmission through the partition.

Sash - An assembly of lightweight aluminum extrusions forming the perimeter of a fixed light of glass.

Sash Balance - A coiled spring or spiral system integrated into the jambs to ease the operation of hung sashes when opening and closing. They also allow the sashes to remain open in varied positions.

Sash Cord - In double-hung windows, the rope or chain which attaches the sash to the counter balance.

Sash Lift - A protruding handle screwed to the inside bottom rail of the lower sash on a double-hung window.

Sash Lock - Generally, a lock applied to the interlocks or stiles of a sliding or hung window to secure the moving panel in place.

Sash Stop - Cover in jamb track that reduces sash travel on hung windows.

Sash Weights - In older double-hung windows, the concealed cast-iron weights which are used to counterbalance the sash.

SBC - Standard Building Code was first enacted by the Southern Building Code Congress International on November 16, 1945. Area of influence was Southeastern portion of the United States. Replaced by the ICC codes.

Screen - Woven mesh of metal, plastic, or fiberglass stretched over a window opening to permit air to pass through, but not insects.

Screw Boss - A continuous screw track in an extrusion. The track is designed to accept a specific diameter sheet metal screw to provide a secure means of fastening extrusions without the use of reinforcement.

Sealant - An elastomeric material with adhesive qualities used to seal joints or openings against the passage of air and water.

Sealant Backing - A compressible material inserted into a joint prior to applying a sealant to limit the depth of the applied sealant. Also see Backer Rod.

Seat Board - A flat board cut to fit the contour of a bow or bay window that's installed between the sills and the flat wall surface. They provide a seat or shelf space.

Seismic Load - Building movement and forces caused by earthquake motion.

Setting Block - A small piece of elastomeric material placed under glass in a frame to distribute the weight of the glass, to center the glass vertically within the frame and to prevent glass-to-metal contact. The recommended durometer for setting block material is 85±5 Shore A scale. Also see Shore A.

Shade Screen - A specially fabricated screen of sheet material with small narrow louvers formed in place to intercept solar radiation striking a window; the louvers are so small that only extremely small insects can pass through. Also called Sun Screen.

Shading Coefficient (SC) - A measure of the ability of a window or skylight to transmit solar heat, relative to that ability for 1/8-inch clear, double-strength, single glass. It is being phased out in favor of the solar heat gain coefficient - approximately equal to the SHGC multiplied by 1.15. It is expressed as a number without units between 0 and 1. The lower a window's solar heat gain coefficient or shading coefficient, the less solar heat it transmits, and the greater is its shading ability.

Shear Block - A type of joinery that uses a clip (the shear block) attached to a vertical mullion. The horizontal member fits over the clip and is secured by screws driven into the shear block.

Sheet Glass - A transparent, flat glass found in older windows, now largely replaced by float glass.

Shim - A spacer of uniform thickness and varying sizes used to plumb and level frames.

Shore A - Test used to measure the durometer (hardness) of elastomeric glazing gaskets and usually referred to as Shore A (Shore Instrument Company - Scale A). Also see Durometer.

Short-Wave Infrared Radia - Invisible radiation, just beyond red light on the electromagnetic spectrum (between 0.7 and 2.5 microns), emitted by hot surfaces and included in solar radiation.

Sidelight - The glazed frame or frames placed on one or both sides of a door.

Silicone - A chemical used as a lubricant or as a sealant.

Sill - The bottom horizontal member of a door, window or sash frame.

Sill Pan - A rigid flashing installed under doors or windows that has a purpose of collecting and draining residual water to the exterior. It can be formed out of sheet metal or extruded in one piece. It is designed to have an upstanding leg in the interior and each end.

Sill track - The track provided at the sill of a sliding glass door or window. Also, the sill member that incorporates such a track.

Simulated Divided Lights - A window that has the appearance of a number of smaller panes of glass separated by muntins, but actually is a larger glazing unit with the muntins placed between or on the surfaces of the glass layers.

Single-Acting Door - A door mounted to swing in one direction only from the plane of its frame.

Single-Glazing - Single thickness of glass in a window or door.

Single-Hung Window - A window consisting of two sashes of glass, the top one stationary and the bottom movable.

Single-Strength Glass - Glass with thickness between 0.085" and 0.100" (2.16­2.57 mm).

Skylight (Operable or Piv - A roof window that gives light and ventilation.

Sliding Glass Door - A door fitted with one or more panels that move horizontally on a track and/or in grooves. Moving action is usually of rolling type (rather than sliding type). Also called gliding door, rolling glass door, and patio sliding door.

Sliding Window - A window fitted with one or more sashes opening by sliding horizontally or vertically in grooves provided by frame members. Vertical sliders may be single- or double-hung.

Slope Glazed - A glass and framing assembly that is sloped more than 15° from vertical.

Smart Window - Generic term for windows with switchable coatings to control solar gain.

Snowload - Loads imposed on slope glazed structures by the accumulation of snow.