The Fenestration Glossary

TERM	MEANING
palladian window	A large, arch-top window flanked by smaller windows on each side.
pane	A framed sheet of glass.
panel	Usually refers to the separate panel or panels in a door frame.
panel	Either an opaque glazing material or the operating portion of a sliding glass door.
panning	a set of extrusions which are fastened to a new window to cover the exterior perimeter of an existing opening in a retrofit application
parting stop	In a double-hung window, a strip of wood applied to the jamb to separate the sash.
passive solar	A solar heating system which operates on natural thermal processes, and that 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.
picture frame casing	The use of casing on all four sides of the interior of a window. The stool and apron at the sill are replaced with casing.
picture window	A large stationary (non-ventilating) window which is designed for a maximum view without obstruction.
picture windows	A type of window using only fixed units -- best for a clear view and energy efficiency.
pleated shade	A shade of folded fabric which can be installed like regular shades or between the panes of glass of a window.
prime frame	a window frame which has an extended perimeter leg 1" back from the window exterior plane, which becomes a nailing fin for new construction installation.
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).
PVC	Poly Vinyl Chloride - in rigid frame/sash members, and in flexible gaskets.
pyrolytic coating	A special coating "sprayed" directly onto glass while it is still in a molten state, resulting in a permanently embedded surface coating.
r value	a measurement of heat resistance (the higher, the better). R value = the number 1 divided by the U value. Resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value.
radiation	The direct process of heat transfer through space by means of electromagnetic waves. Energy in the form of rays of light is transferred from body to body without heating the intermediate air.
rail	The top and bottom horizontal members of the framework of a window sash or door panel. a horizontal sash member.
receptor	framing system consisting of two snap-together extrusions used to contain a window frame head and jambs in a masonry type opening. It allows for deflection and inconsistencies in the openings.
reflectance back.	A measurement in percentage of the visible light reflected back into a room. For ease of seeing to the outside, a lower rating is better
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	glass with metallic coatings applied onto or into the glass surface to reduce solar radiant energy and visible light transmission
relative heat gain	A measurement of the total heat gain through glazing for a specific set of conditions.
relative humidity	Humidity expressed as a percentage of the maximum possible humidity at a given temperature.
removable grilles	Ornamental or simulated muntins and bars designed to provide a divided light appearance. Generally made of wood, they are applied to the inside of the sash against the glass surface for easy removal.
rough opening	The opening built into a frame wall to receive a window or door unit. It is formed with a header along the top that’s supported by jack studs on each side. The rough sill at the bottom is supported by cripples. A rough opening is generally greater in width and height than the window or door unit. The framed opening in a wall into which a window or door unit is to be installed.
rough sill	The horizontal framing piece, usually a 2x4, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and supported by cripples.