What's the difference between an R-Value and a U-Value? Here's a helpful list of fire-rated glass & framing terms, along with their definitions.
Active Door - (in a pair of doors) - The leaf that opens first, and the one to which the lock is applied.
ANSI - American National Standards Institute (ANSI Z97.1)
Astragal - A member or combination of members applied to one or both doors of a pair at their meeting edges. The astragal closes the clearance gap for the purpose of either providing a weather seal, minimizing the passage of light between the doors or retarding the passage of smoke or flame during a fire. Some types overlay, others meet at the centerline of the gap (sometimes referred to as a split astragal).
Backcheck - Optional feature in hydraulic door closers (Dorma TS-93), which takes effect at a certain degree of opening and controls the speed of the door during the balance of its opening cycle.
Backset (of a lock) - A term used if referring to the horizontal distance from the face of the lock to the centerline of the cylinder, key hole, or knob hub. On locks with beveled fronts, this distance is measured from the center of the lock edge. On locks with rabbeted fronts it is measured from the lower step of the lock face.
Ball-Bearing Hinge - A hinge equipped with ball bearings between the hinge knuckles to reduce friction.
Borrowed Lite - A glazed opening in a room with no exterior glazing, allowing the room to "borrow" natural light from adjoining space.
Building Compartmentation - The concept that buildings can be sub-divided into a number of compartments using fire-rated building materials to help slow or stop the spread of fire.
Butt-Hinge - A hinge mortised into both the door and frame.
Cap Seal/Cap Bead - A bead of sealant applied so as to have a slanted top surface to shed water away from the glass. Minimum cap bead depth should be 3/16".
Center Pivot - A special type of hanging device for heavy-duty doors that usually swing both ways (double acting).
Ceramic - Material known for its outstanding heat resistance. Used in certain fire-rated glazing materials, such as the FireLite family of products.
Coordinator - A device used on a pair of doors to insure that the inactive leaf closes first, before the active leaf. Necessary when an overlapping astragal is present, with certain exit device combinations, and when automatic or self-latching bolts are used. Both door leaves must have closers.
CPSC - Consumer Products Safety Commission (CPSC 16CFR 1201)
Curtain Wall - An exterior wall that provides no structural support.
Cylinder - The part of a lock that contains the tumbler mechanism and keyway. The cylinder will permit only the correct key to enter and turn, thus operating the mechanism.
Cylindrical Lock - A type of bored lock. The locking mechanism is usually contained within a cylindrical case, and actuated by a cylinder and/or a button in the knob.
Deadbolt - A lock bolt having no spring action, usually rectangular in shape, which is operated by a key or turnknob. It is locked against end pressure when projected.
Dogging - Term used with exit devices. A mechanism that allows the latchbolt to remain in a retracted position thus permitting free push-pull operation of the door from either side. Cannot be used on fire-rated devices.
Door Closer - (or Door Check) - A device attached at the top of the door, either on the surface or mortised, to regulate and control the operation of the door.
Door Pull - A handle or grip, commonly mounted on a plate, designed for attachment to a door to facilitate opening and closing.
Door Stop - A device to limit the opening swing of a door. Also, that part of a door frame against which the door closes.
Double Egress - A pair of doors that are comprised of two single-acting doors swinging in opposite directions, both doors being of the same hand.
Double-Acting Door - A door equipped with hardware that permits it to swing to either side of the plane of its frame.
Electric Strike - An electrical device that replaces a regular lock strike and allows opening of the door from a remote location or by special access equipment.
Exit Device - A door locking device designed to grant instant exit from an area, by pressing on a crossbar, which releases the locking bolt or latch.
Extrusion - The process of producing metal shapes by forcing heated metal through an orifice in a die by means of a pressure arm; any item made by this process.
Fire Door - The operable component of a fire door assembly designed to provide a specific degree of fire protection, while at the same time allowing building occupants to pass through.
Fire Door Assembly - Any combination of a fire door, a frame, hardware, and other accessories that together provide a specific degree of fire protection to the opening.
Fire Door Frame for Lites - A frame that, in addition to a door opening, contains an opening(s) for use with glazing materials. Various types include transom lite, sidelite, and transom and sidelite frames.
Fire Protection Rating - The designation indicating the duration of the fire test exposure to which a fire door assembly or fire window assembly was exposed and for which it successfully met all acceptance criteria as determined in accordance with NFPA 252 / NFPA 257 / UL 9 / UL 10C / ASTM E-163 / ASTM E-152.
Fire Protective - Glass that defends against the spread of flames and smoke for its designated fire rating.
Fire Resistance Rating - The time, in minutes or hours, that materials or assemblies have withstood a fire exposure as established in accordance with the test procedures of NFPA 215 / ASTM E-119 / UL 263. (Wall Assemblies)
Fire Resistive - Glass that defends against the spread of flames, smoke and radiant and conductive heat transfer for its designated fire rating.
Fire Stopping - Obstructions across air passages in buildings to prevent the spread of hot gases and flames; horizontal blocking between wall studs.
Fire Wall - A wall extending from foundation through the roof to subdivide a building in order to restrict the spread of fire.
Fireproofing - Any material protecting structural members to increase their fire resistance.
Flashing - The sheet metal work used to prevent leakage over windows and doors, around chimneys, and at the intersection of different wall surface and roof planes.
Float Glass - Glass formed on a bath of molten tin.
Floor Closer - A door closing device that is installed in a recess the floor below the door in order to regulate and control the opening and closing of the door.
Flush Bolt - A door bolt so designed that when installed it is flush with the face or edge of a door.
Full Mortise - Hinge with one leaf mortised in the edge of the door, the other mortised in the door jamb.
Full Surface - Hinge with one leaf secured to the surface of the door, the other secured to surface of door jamb.
Glass Ceramic - See ceramic. Also, see FireLite.
Half-Mortise - Hinge with one leaf mortised in the edge of the door, the other leaf secured to the surface of door jamb.
Half-Surface - Hinge with one leaf mortised in door jamb, and the other leaf secured to the surface of the door.
Hand - The term used to indicate the direction a door swings.
Hardware Sets - A group hardware listed in the specification, under execution, for a specific opening.
Heat Transfer - (ASTM E-119 / UL 263)
Hinge - Two jointed plates hinged together and attached to a door and its frame. Serves to support or "hang" the door and allows the door to swing or move.
Hinge Types - Classified according to installation method.
Hose Stream Test - In the U.S., the hose stream test is required for all fire ratings over 45 minutes (all fire ratings require it in Canada). Immediately following a furnace test, heated glass is subjected to water from a fire hose. The cooling, impact and erosion created by the hose stream tests the integrity of the glass and eliminates inadequate materials.
Impact Safety Rating - Measures the ability of glass to withstand impact. Ratings are given in levels based on the amount of force the glass can resist. Impact safety ratings are often required where glass is regularly exposed to contact by people or objects.
Inactive Door - The leaf of a pair of doors that is bolted when closed, and to which the lock strike is fastened to receive the latch of the active door.
Jamb - The vertical member forming the side of a door, window or wall opening frame. The hinge jamb is the jamb at which the hinges or pivots are installed. The strike jamb is the jamb in which a strike may be installed and away from which the door or window swings. A blank jamb is one that has not been prepared to receive hardware.
Kick Plate - A protective plate applied on the lower rail of the door to protect against the door being marred.
Knocked Down - A term used in reference to any product that is shipped disassembled, for assembly at the building site, commonly abbreviated "KD".
Labeled Door (or Frame) - A door or frame that conforms to all the applicable requirements - in respect to fire resistance - of a nationally recognized testing authority and bears a label designating the fire rating.
Laminated Glass - Two or more lites of glass permanently bonded together with one or more interlayers.
Latchbolt - A lock component having a beveled end that projects from the lock front but may be forced back into the lock case by end pressure or drawn back by action of the lock mechanism. When the door is closed, the latchbolt projects into a hole provided in the strike, holding the door in a closed position.
Leaf - One of the two doors forming a pair or a double door.
Lever Handle - A horizontal handle on a lockset or auxiliary lock.
Lockset - A complete lock or latch assembly, includes the lock or latch mechanism and trim (knobs, levers, handles, roses, and escutcheons).
Monolithic Glass - Glass composed of a single layer.
Mortise - An opening, recess or cutout made to receive a lock or other hardware. Also, the act of making such an opening.
Mortise cylinder - A cylinder with a threaded body and a cam. Normally used with mortise locks.
Mortise Lock - A lock assembly designed to be mortised into the edge cut out in a door.
NFPA - National Fire Protection Agency
Offset Pivot - A special hanging device for heavy-duty doors, used on doors swinging one way only.
Overhead Concealed Closer - A closer concealed in the frame header with an arm connecting to the door at the top rail.
Panic Hardware - See Exit Device.
Pre-Assembled Lock - A lockset that has all the parts assembled as a unit at the factory. Requires little or no assembly for installation. Installs into a rectangular notch cut into the door edge.
Premium Grade - Clear FireLite that has been polished for superior optical clarity.
R-Value - The thermal resistance of a glazing system expressed in ft2/hr/F/BTU. The R-Value is the reciprocal of the U-Value. The higher the R-Value, the less heat is transmitted throughout the glazing material.
Rail - A full thickness, horizontal structural member forming the top or bottom edge of a door or sash. May be located at an intermediate height in a door, separating panels or glazed areas.
Reveal (of a door frame) - That part of a back bend that projects out from the finished wall. Also, the dimension from the inside face of the door to the face of the frame at the side opposite from the direction of the door swing.
Rim - A term indicating articles of hardware designed for application to the surface of the door or frame.
Rim cylinder - Mounted through the door independently of the lock, usually by screws from the reverse side, and engaging the lock mechanism by means of a tailpiece.
Safety Rating - See impact safety rating
Shim - A piece of material used to true up or fill in the space between two surfaces.
Sidelite - The glazed frame or frames placed on one or both sides of a door.
Single-Acting Door - A door mounted to swing to only one side of the plane of its frame.
Sound Transmission Class (STC) - A single number rating derived from individual transmission losses at specified test frequencies. It is used for interior walls, ceilings, and floors and in the past was also used for preliminary comparison of the performance of various glazing materials.
Standard Grade - Clear but unpolished FireLite that will have a slight surface distortion/waviness similar to that of antique glass. Not recommended for large lites of glass where high optical quality is required (see “premium grade”). Recommended for smaller lites such as small door lites where optical quality is not important.
Stile - The vertical members of a door to which the lock and the hinges are applied.
Strike - A metal plate or box that is pierced or recessed to receive the bolt or latch of a lock. Sometimes called a "keeper".
Surface Bolt - A rod or bolt mounted on the face of the inactive door of a pair to lock it to the frame and/or sill; operated manually.
Tempered Glass - Flat or bent glass that has been heat-treated to a high surface and or/edge compression. Fully tempered glass, if broken, will fracture into many small pieces (dice) which are more or less cubical. Fully tempered glass is approx. four times stronger than annealed glass of the same thickness. (Outside of North America sometimes called "toughened glass").
Thermal Endurance - The relative ability of glass to withstand thermal shock.
Thermal shock - Since glass expands and contracts with temperature changes, it experiences stress when its surfaces are exposed to contrasting temperatures at the same time. Glass that cannot withstand this "thermal shock" will shatter or explode out of the frame under these conditions, and therefore cannot receive a fire rating greater than 20 minutes in the United States.
Throw - The distance that a deadbolt or latchbolt projects when in the locked position.
Transom - An opening in a door frame above the door opening that is filled by a solid panel or with glazing material.
U-Value - A measure of air-to-air heat transmission (loss or gain) due to thermal conductance and the difference in indoor and outdoor temperatures. As the U-Value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-Value, the more restrictive the fenestration product is to heat transfer (Reciprocal of the R-Value).
Wired Glass (polished) - Rolled glass having a layer of meshed wire completely imbedded as nearly as possible to the center of the thickness of the lite. Approved polished wired glass is used as transparent or translucent fire protection rated glazing. It breaks more easily than unwired glass of the same thickness.