Gable - The triangular end of an exterior wall above the eaves of a pitched roof.
Gable roof - A roof which slopes from two sides only.
Gable stud - The stud at the gable of a roof where the exterior finish is applied.
Gang nail plate - A steel plate attached to both sides at each joint of a truss.
Gate valve - A valve that lets you completely stopbut not modulatethe flow within a pipe.
Generating capacity - The total amount of electrical power that a utility can produce at any one time.
Geothermal energy - Energy from hot water or steam warmed deep inside the earth's crust.
GFI or GFCI or ground fault current interrupter - A electrical device used to prevent injury from contact with electrical appliances. Required in new homes in: bathrooms, kitchen, garage, out of doors and in other locations where one might be in contact with a grounded surface and an electrical appliance. Most GFIs are located in the receptacle itself and can be identified by the presence of a 'test' and a 'reset' button.
Girder (floor girder) - A horizontal beam supporting the floor joists.
Glauber's salts - A phase-change material.
Glazing - The process of installing glass, which commonly is secured with glazier's points and glazing compound.
Globe valve - A valve that lets you adjust the flow of water to any rate between fully on and fully off. Also see gate valve.
Grade - Ground level, or the elevation at any given point.
Grain - The direction of fibers in lumber or other materials.
Ground - Refers to electricity's habit of seeking the shortest route to earth. Neutral wires carry it there in all circuits. An additional grounding wire or the sheathing of metal-clad cable or conduitprotects against shock if the neutral leg is interrupted.
Groundwater - Water from an aquifer or subsurface water source.
Grout - Thin mortar that fills the joints between tiles or other masonry.
Gypsum board - See drywall.
Hardboard - A manufactured building material made by pressing wood fibers into sheet goods.
Header - Heavier framingusually doubled and laid on edge at the top of a window, door, or
other opening. In masonry, a header course of bricks or stones laid on edge provides strength.
Heat capacity - The quantity of heat that a given volume of a material can hold for each unit increase in temperature, usually given in terms of Btu's per degree Fahrenheit per cubic foot.
Heat exchanger - A device, usually made of coils of pipe, that transfers heat from one medium to another; for example, from water to air or water to water.
Heat gain - Heat coming into a home from sources other than its heating/cooling system. Most gains come from the sun.
Heat loss - Heat escaping from a home usually to outside air. Heat gains and losses are expressed in Btu's per hour.
Heat of fusion - The quantity of heat released when a material freezes or absorbed when it melts (in Btu's per pound).
Heat pump - A device which uses compression and decompression of gas to heat and/or cool a house.
Heating load - The amount of heating required to keep a building at a specified temperature during the winter, usually 65·F, regardless of outside temperature.
Heating season - The time period during which a building needs to be heated.
HID (high intensity discharge) lamp - A lamp that operates in the same way as a fluorescent tube, but that has a bulb like incandescent lamps.
Hip roof - A roof with four sloping sides.
Hot wire - The wire that carries electrical energy to a receptacle or other devicein contrast to a neutral, which carries electricity away again. Also see ground.
Humidity - The quantity of water vapor contained in air (in pounds per pound of air).
Hybrid system - A solar system that combines both active and passive elements, for example, a passive system that contains fans or blowers to aid heat circulation.
Hydronic Heating - A heating system which uses various types of fuel to heat water which is then distributed through pipes to radiators located in various portions of the house.
Hydropower - Energy produced by water, for example, at a hydroelectric dam.