Buildings and Architecture Glossary: G - I

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- G -

Gable: A roof consisting of two sloping surfaces that intersect at a level ridge; the triangular end wall of such a roof.

Gasket: An elastic strip used to seal a joint between two adjacent components.

Glare: Excessive contrast in brightness between a visual task and its surroundings.

Glass, heat-absorbing: Glass that is tinted so that it absorbs heat from light that passes through it.

Glass, heat-reflecting: Glass that is coated with a reflecting layer that bounces back a portion of incident light and heat.

Glass, laminated: Two surface layers of glass bonded to a viscous plastic core.

Glazed: Having a glassy surface.

Glazing: The installation of glass in a building. A transparent material, usually glass, in a window. The application of a glassy finish layer to a ceramic material.

Glazing compound: A mastic in which glass is bedded in a window sash.

Glazing, double or triple: Two or three sheets of glass with air spaces between.

Grade beam: A concrete beam that spans across isolated foundation elements to provide continuous support for a wall.

Greenhouse effect: The trapping of solar heat behind a barrier such as glass in a building or a layer of selectively transparent gases in the earth’s atmosphere.

Ground fault interrupter: A device that shuts off the flow of electricity in a circuit if current leaks from the circuit to the ground.

Gutter: A sloping channel that gathers water from the low edge of a roof surface and conducts it to a downspout.

Guy: A sloping cable that stabilizes a vertical structural element.

Gypsum: A naturally occurring mineral, calcium sulfate hemi hydrate, used to make plaster, wallboard, fireproofing, and other building materials.

- H -

Hard water: See Water, hard.

Heat exchanger: A device for transferring heat from one medium to another, such as water to air or air to air.

Heat pump: A device that utilizes either a compression cycle or an absorption cycle to move heat from a cooler medium to a warmer one.

Heat sink: A mass or substance with a very large thermal capacity compared to the amounts of heat flowing through a system.

HID, High-intensity discharge lamp: A type of high-efficiency device for artificial lighting.

Hopper window: A sash that is hinged along the bottom edge and tilts inward to open.

Horizontal exit: See Exit, horizontal.

Hot wire: A current-carrying electric wire that is not connected to the ground.

Humidity, relative: The ratio of the amount of water vapor contained by a given mass of air to the maximum amount of water vapor it could contain at the given temperature.

Hydronic: A system that uses hot water to distribute heat within a building.

Hyperbolic paraboloid shell: A thin, saddle-shaped concrete slab used as a self-supporting structure.

Hypothermia: A condition in which the human body is unable to maintain its normal core temperature.

- I -

Ice dam: A barrier of frozen water across the cave of a roof behind which liquid water accumulates.

Incandescent: Emitting light as a result of being at a very high temperature.

Infiltration: The movement of air in or out through cracks and defects in the enclosure of the building.

Infrared: Electromagnetic wavelengths longer than those of red light.

Intumescent coating: A layer of paint or mastic that expands to form a stable, insulating char when exposed to the heat of a fire.

Inverse square law: Radiational intensity from a point source is inversely proportional to the square of distance from the source.

Inversion: See Atmospheric inversion.

Inverted roof: A low-slope roof construction in which polystyrene foam insulation is placed above the waterproof membrane.

Invertibility: When any structure is turned upside down with its external loads remaining in their original positions and directions, the force in each member of the structure changes from tension to compression or vice versa.

Isolated footing: A concrete foundation element that supports a single column by spreading its load over a large area of soil.

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