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Double-Strength Glass Sheet glass between 0.115" and 0.133" (33.38 mm) thick. Dowel Cylindrical wood peg fitted into a hove drilled through two pieces of wood. Down Flow A type of furnace that takes cool air from the top and blows warm air to the bottom - common when your furnace must be located in a second-floor closet or utility area. Downdraft A downward current of air in a chimney, often carrying smoke with it. Downspout A pipe for draining water from roof gutters. Also called a leader. Downtime The time to locate a fault and then repair it. Drainage A system of drains, e.g., tiles, pipes, conduits, designed to remove surface or subsurface water or waste water and sewage. Draught/Draft Excessive air movement in an occupied enclosure causing discomfort. Draught Proofing/ Draft Proofing The action of filling the gaps around doors and windows, in order to prevent outside cold air leaking into the building, causing draughts. Drip A projecting fin or a groove at the outer edge of a sill, soffit, or other projecting member in a wall designed to interrupt the flow of water downward over the wall or inward across the soffit. Drip Edge A non-corrosive, non-staining material used along the eaves and rakes to allow water run-off to drip clear of underlying construction. Dry Bulb The ambient outside temperature. Dry Bulb Temperature The temperature indicated by a dry temperature-sensing element (such as the bulb of mercury in a glass thermometer) shielded from the effects of radiation. (see wet bulb temperature) Dry Rot A decay of seasoned wood caused by fungus. Drywall Any finish material applied to an interior wall in a dry state, as distinguished from plaster, e.g., gypsum wallboard, plywood, fiberwood. Drywall Construction A type of interior wall construction using wood paneling, plywood, plasterboard, or any other type of wallboard instead of plaster as the finish material. Duct Large channel through which air passes in a heating, cooling or exhaust system. Ductwork / Duct System The duct system is a direct extension of the heating and cooling equipment. This is the part of the heating/cooling system which moves the air from the heating/cooling equipment to the various rooms. All duct systems must be sized to your individual needs and be insulated. A leaky duct system can not only cause you to loose heating efficiency, but cause you health problems as well. Duplex A house containing two separate dwelling units, side by side or above the other also describes apartments that occupy two levels or a portion of two floors. Dutch Door A door divided horizontally in the middle so that the bottom half can remain closed while the top is open. Dutch Lap Method Application of giant individual shingles with the long dimension parallel to the eaves. Shingles are applied to overlay adjacent shingles in each course as well as the course below. Eaves The horizontal, lower edge of a roof which projects beyond the building wall. Eaves Closure That component of a tile roofing system which is used to seal the openings along the eaves of a structure under the first layer of tile. Also called closure tile. Eaves Flashing Additional layer of roofing material applied at the eaves to help prevent damage from water back-up. Ebulator A pointed or sharp edged solid substance inserted in flooded type evaporators to improve evaporation (boiling) of refrigerant in coil. Eccentric A circle or disk mounted off center. Eccentrics are used to adjust controls and connect compressor driveshafts to pistons. Econimizer A mechanism that removes flash gas from the evaporator. Economizer Control An energy management function, which aims to minimize energy consumption by the use of 'free-cooling'. Internal heat generation in a building may require the HVAC to provide cooling, even though the air temperatures are lower than the thermostat set point. Under this condition, it is possible to introduce outdoor air into the building to provide all or part of the cooling normally accomplished by refrigeration equipment. To use this' free-cooling', the economizer measures the dry-bulb temperature of the return air and the outdoor air, and selects an appropriate amount of the cooler air for the building conditioning by adjusting outdoors, return, and exhaust dampers. Eddy Currents Induced currents flowing in a core. Edge Effects Two-dimensional heat transfer at the edge of a glazing unit due to the thermal properties of spacers and sealants. Edging Strips Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for reroofing with asphalt shingles. EER Energy Efficiency Rate This is a simple mathematical ratio of cooling output measured in British thermal units per hour (Btuh) versus electrical power input (watts). A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at a given set of rating conditions, expressed in Btuh per watt (Btuh/watt). Effective Area Actual flow area of an air inlet or outlet. Gross area minus area of vanes or grille bars. |