Calcium Carbonate or Efflorescence - A white chalky material which is very often found in concrete basement walls and other concrete surfaces where water has leached some of the chemicals out of the concrete. Usually a sign of past or present moisture penetrations.
Cantilever - A beam or beams projecting beyond a support member.
Casement Window - A window with hinges on one of the vertical sides and swings open like a normal door (see diagram).
Casing - Trim work around a door, window, or other opening.
Caulking - A flexible material used to seal a gap between two surfaces e.g. between pieces of siding or the corners in tub walls.
Ceiling joist - One of a series of parallel framing members used to support ceiling loads and supported in turn by larger beams, girders or bearing walls.
Cement - A powder that serves as the binding element in concrete and mortar. Also, any adhesive.
Ceramic tile - A man-made or machine-made clay tile used to finish a floor or wall.
CFM (cubic feet per minute). A rating that expresses the amount of air a blower or fan can move.
Chalking - The tendency of some exterior paints to gradually erode away over a period of time.
Change order - A written document which modifies the plans and specifications and/or the price of the construction Contract.
Chip board - see Oriented Strand Board
Circuit breaker - A protective switch that automatically shuts off current in the event of a short or overload. Also see fuse, short circuit.
Class "A" - Optimum fire rating issued by Underwriter's Laboratories on roofing. The building code in some areas requires this type of roofing for fire safety.
Class "C" - Minimum fire rating issued by the Underwriters' Laboratories for roofing materials.
Clerestory - A vertical window located on a flat or pitched roof.
Cogeneration - The simultaneous production of heat and electricity in one system.
Collector - A glazed device, wall or window that captures sunlight for the purpose of providing space heat and domestic hot water.
Combustion chamber - The part of a boiler, furnace or woodstove where the burn occurs; normally lined with firebrick or molded or sprayed insulation; heat exchanger, which transfers heat to the air, water or steam distribution system, forms part of its walls.
Combustion efficiency - A measurable number that indicates the percentage of energy content in a fuel that is converted to heat; number is measured when heater is running in a stable, steady state.
Compression web - A member of a truss which connects the bottom and top chords and provides downward support.
Compressor - A mechanical device that pressurizes a gas in order to turn it into a liquid, thereby allowing heat to be removed or added; compressor is main component of conventional heat pumps and air conditioners.
Concrete - A basic building and paving material made by mixing water with sand, gravel, and cement often used for foundations, ground level floors, and sidewalks. Most concrete is made out of (1) Portland cement, (2) sand, and (3) gravel or aggregate. It is commonly reinforced with steel rods (rebar) or wire screening (mesh).
Concrete block - A hollow concrete 'brick' often 8" x 8" x 16" in size. Often used in low rise commercial and some residential construction.
Concrete board or Wonderboard - A panel made out of concrete and fiberglass usually used as a tile backing material.
Condensing unit - The outdoor segment of a cooling system. It includes a compressor and
condensing coil designed to give off heat. Also see evaporator coil.
Conduction - The direct transfer of heat energy through a material.
Conductivity - The rate at which heat is transmitted through a material.
Conduit - A metal tube used to run, house or contain electrical wire.
Contractor - A company licensed to perform certain types of construction activities. In most states, the generals contractor's license and some specialty contractor's licenses don't require of compliance with bonding, workmen's compensation and similar regulations. Some of the specialty contractor licenses involve extensive training, testing and/or insurance requirements. There are various types of contractors:
Convection - Currents created by heating air, which then rises and pulls cooler air behind it. Also see radiation.
Cooling load - The amount of cooling required to keep a building at a specified temperature during the summer, usually 78·F, regardless of outside temperature.
Cooling season - That time period each year during which a building needs to be cooled.
COP (coefficient of performance) - A measure of the efficiency of any heating unit— arrived at by dividing its output in BTUs by its input in BTUs.
Coping - A cap at the top of a wall that's rounded or beveled to shed water. Also, a curved cut made so that one contoured molding can join neatly with another.
Cord - 128 cubic feet of firewood. It is usually a stack eight feet long, four feet wide and four feet high.
Corner bead - Lightweight, perforated metal angle used to reinforce outside corners in drywall construction.
Corner assembly - The framing members used to change direction in an interior-exterior wall.
Corner brace - Diagonal supports set into studs to reinforce the area where a wall changes direction in a frame structure. In many areas plywood is used.
Cornice - The projection from a building that crowns or finishes the edge. Horizontal projection at the top of exterior wall which finishes the eaves of a building.
Courses - Parallel layers of building materials such as bricks, shingles, or siding laid up horizontally.
Cove - A concave curve where vertical and horizontal surfaces join.
Crawl space - Space between floor and ground of a house or building.
Cripples - Short studs above or below a door or window opening.
Crown - Paving slightly humped so that water will run off. Also a contoured molding sometimes installed at the junctures of walls and ceilings.
Cupping - A type of warping that causes boards to curl up at their edges.
Cut-in velocity - The wind speed at which a wind machine (usually a horizontal axis machine) begins to turn and generate electricity.
Cut-out velocity - The wind speed at which a wind machine stops turning in order to protect against blade damage and generator burn-out.
Dado - A groove cut into a board or panel intended to receive the edge of a connecting board or panel.
Damper - A valve inside a duct or flue that can be used to slow or stop the flow of air or smoke.
Dampproofing - The coating applied to the exterior of a foundation wall with a waterproofing material such as foundation coating.
Dead band control - A control subsystem on a thermostat that allows the heating or cooling system to remain on until room temperatures exceed the set temperature by several degrees.
Degree-day (DD) - A measure of climatic severity used to estimate heating or cooling energy consumption; for heating, if average outdoor temperature for a day is 10· below 65·F (or 55·F), the day has 10 heating degree-days.
De-humidistat - A control mechanism used to operate a mechanical ventilation system based upon the relative humidity in the home.
Delta T - The difference between two temperatures.
Design-day heat load - The total heat load of a structure under the most severe conditions (temperature and wind) likely to occur; estimates of these conditions generally based on 30 years of weather records and quote a figure which will be exceeded only 1 percent of the time.
Design temperature - The most severe temperature likely in a given location.
Designer - One who designs houses, interiors, landscaping or other objects. When used it the context of residential construction it usually suggests that a designer is not a licensed architect. Most jurisdictions don't require an architectural license for most single family construction.
Direct-gain system - A passive solar heating system in which the collector is a window opening into the living space.
Distribution efficiency - The efficiency with which a heating system provides heat to a building.
District heating - Heating of buildings by hot water or steam produced at a central boiler and distributed through a network of pipes.
Double hung window - A window with two vertically sliding sashes. This is a very common older window design, was usually made out of wood and tends to require frequent repairs.
Dead bolt - A locking device that can be activated only with a key or thumb turn. Unlike a latch, which has a beveled tongue, dead bolts have square ends.
Decking - The material installed over the supporting framing members to which the roofing material is applied.
Directional Light - Light intensity at the center of the beam. Used for flood and spot light bulbs types.
Do-it-yourself (DIY) - The process of doing any project by oneself. Some may traditionally have been contracted out to a professional or in the case of a klutz done by one's spouse or father-in-law. If necessity is the mother of invention it is also the father of DIY.
Dormer - A small pitched structure projecting from a roof, usually with a vertical window.
Double cylinder - A type of lock that must be operated with a key from inside as well as outside.
Double-hung window - A window that has a top sash and bottom sash, both of which move up and down.
Double-pane window - Two panes of glass sealed at the edges to create dead air space. The sealed air acts as an insulator.
Downsizing - Measures taken to reduce a heating system's capacity to make it more compatible with a building's heating requirements; often done following major weatherization.
Drain-back - An active liquid solar system that empties the collectors and pipes, storing the liquid in a reservoir; system avoids freeze-up problems.
Drain-down - Similar to drain-back systems, except the liquid is thrown away (to the house drains) each time the collectors are emptied.
Drain tile - A perforated, corrugated plastic pipe laid at the bottom of the foundation wall used to drain excess water away from the foundation. It prevents water from seeping through the foundation wall.
Drying in - The construction process generally considered to be from the foundation plate up through the application of exterior finish materials.
Dry rot - see Fungal wood rot
Drywall or Gypsum Wallboard (GWB) or Sheet rock or Plasterboard - A wall finish consisting of a manufactured panel made out of gypsum plaster and encased in a thin cardboard. Usually +" thick and 4' x 8' or 4' x 12' in size. The panels are nailed or screwed onto the framing and the joints are taped and covered with a 'joint compound'. 'Green board' type drywall has a greater resistance to moisture than regular (white) plasterboard.
Dry wall - A masonry wall laid up without mortar.
Drywall - A basic interior building material consisting of big sheets of pressed gypsum faced with heavy paper on both sides. Also known as gypsum board, plasterboard, and Sheetrock (a trade name).
Duct - A tunnel made of galvanized metal or rigid fiberglass, which carries air from the heater or ventilation opening to the rooms in a building.
DWV (drain-waste-vent) - The section of a plumbing system that carries water and sewer gases out of a home.