UL (Underwriters' Laboratories) - An independent testing agency that checks electrical and other components for possible safety hazards.
Underlayment - Top layer of plywood (or other material) in a two-layer floor. Provides a smooth base for carpet, tile or sheet flooring.
Union - A plumbing fitting that joins pipes end-to-end so they can be dismantled.
Utility grid - The combination of electric power plants and transmission lines belonging to an electric utility.
UURHOT - An unused underground residential heating oil tank. Usually found in homes which were once heated with oil.
U-value (coefficient of heat transmission) - The rate of heat transmission through 1 square foot of building envelope for 1 degree Fahrenheit difference in temperature between indoors and outdoors.
Valley - The intersection of two roof slopes.
Vapor barrier - A waterproof membrane in a floor, wall, or ceiling that blocks the transfer of condensation.
Vaporization - The process of converting a liquid gas, either by addition of heat or reduction of pressure.
Volt (V) - A measure of electrical pressure. Volts x amps=watts.
Warranty - In construction there are two general types of warrantees. One is provided by the manufacturer of a product such as roofing material or an appliance. The second is a warrantee for the labor. For example, a roofing contract may include a 30 year material warrantee a and a 5 year labor warrantee. Many (but not all ) new homes come with a one-year warranty. Any major issues found during the first year should be communicated the builder at once. Small items can be saved up and presented to the builder in a letter on the 11 month anniversary of the closing. This gives the builder one month to make the necessary corrections.
Warping - Any distortion in a material.
Watt (W) - A measure of the power an electrical device consumes. Watt hours (WH) express the quantity of energy consumed. Also see volt, amp, and kilowatt.
Weatherization - Modifying a building envelope to reduce energy consumption for heating or cooling; involves adding insulation, installing storm windows and doors, caulking cracks and putting on weather-stripping.
Weather-stripping - A narrow strip of material, such as plastic, felt or metal, which is installed around windows and doors to reduce the infiltration of air between them and their frames.
Weep holes - Small holes in storm window frames that allow moisture to escape.
Window frame - The stationary part of a window unit; window sash fits into the window frame.
Window sash - The operating or movable part of a window; the sash is made of window panes and their rim.
Wind shear - A change in wind direction or velocity over a very small standard distance; the standard distance is usually equal to the rotor diameter of a wind machine.
Work - The transfer of energy from one system to another; for example, heat transferred by a heat pump from source to sink.