|Design Handbook on Passive Solar Heating and Natural Cooling (HABITAT, 1990, 162 p.)|
absorbent. A material which, due to an affinity for certain substances. extracts one or more such substances from a liquid or gaseous medium with which it contracts and which changes physically or chemically, or both, during the process.
absorber. A solar absorber Is any dark (black) device used to collect the sun's energy. Usually it refers to the black flat plate absorber used with solar water-heating systems.
absorption ratio. The ratio of the radiation absorbed by a surface to the total energy falling on the surface measured as a percentage.
active solar-energy system. A system which requires the importation of solar energy from outside the Immediate environment; for example, energy to operate fans and pumps.
active systems. Systems which convert energy Into an appropriate form for the benefit of occupants in a house. An oil heater Is making use of an active system.
adsorbent. A material which has the ability to cause molecules of gases, liquids or solids to adhere to its internal surfaces without changing the adsorbent physically or chemically.
air, ambilent. Generally, the air surrounding an object.
air, recirculation. Return air passed through an air-conditioner before being resupplied to the conditioned space.
air, saturated. Moist air in which the partial pressure of wader vapour equals the vapour pressure of wafer at the existing temperature. This occurs when dry air and saturated water vapour coexist at the same dry bulb temperature.
air, standard. Dry air of a pressure of 760m,m (29.92 in) Hg an 21°C(69.8°F) temperature and with a specific volume of 0.833m /kg(13.33ft~/lb.).
air changes. A method of expressing the amount of air leakage into or out of a building or room in terms of the number of building or room volumes exchanged.
air changes per hour. The number of times that the air leakage Into or out of a building or room in terms of the number of building or room volumes exchanged.
air-conditioning, summer. Comfort air-conditioning used primarily when outside temperature and humidity are above those to be maintained in the conditioned space.
dr-conditioning, winter. Heating, humidificadion, air distribution and air cleaning where outside temperature and humidity are lower than those to be maintained in the conditioned space.
air-conditioning unit. An assembly of equipment for the air treatment to control simultaneously its temperature humidity cleanliness and distribution to meet the requirements of a conditioned space.
air cooler, dry. Removes sensible heat from the dehydrated air whenever it leaves the dehydrator at an elevated temperature.
air cooler, dry-type. A forced circulation air cooler where heat transfer is not implemented by a liquid spray while in operation.
air cooler, forced circulation. A cooler including a fan or a blower for positive circulation.
air cooler, free delivery. A cooler taking air from and discharging it directly to the space to be treaded without an element external to the cooler to impose air resistance.
air cooler, natural convection. An air cooler depending on natural convection to aid circulation.
ambient air temperature. Surrounding temperature to the environment; for example, air temperature around a dwelling.
ambient temperature, effective. For elements surrounded by air or other fluid, a suitably weighted mean between the air or fluid temperature and the mean radiant temperature of the surroundings.
auxiliary system. A supplementary heating unit to provide heat to a space when its primary unit cannot do so. This usually occurs during periods of cloudiness or intense cold, when a solar heating system cannot provide enough heat to meet the needs of the space. Also called
"back-up" system. azimuth. The angular distance east or west of the meridian in the horizontal plane.
bats. A non-rigid fibrous mat usually of rectangular cross- section, no greater than 3 m in length.
berm. A man-made mound or small hill of earth.
blanket. A non-rigid fibrous mat usually of rectangular cross section, greater than 3 m in length. bulk thermal insulation. Materials in the form of batts, blankets, slabs or loose fill, or foamed in situ.
cellulose fibre. Material of a fibrous nature made from wood. paper or vegetable fibres.
clerestorey window. A small window or row of windows high in a wall below the ceiling.
Clot. The unit of measurement for the thermal effect of clothing on the human body. One clot is an arbitrary unit of clothing Insulation equivalent to the amount of clothing needed to maintain the comfort of an Inactive person in still air at 20C for relative humidities less than 50 per cent.
collector, flat-plate. An assembly containing a panel of metal or other suitable material, usually of flat black colour, that absorbs sunlight and converts it into heat. This panel is usually In an insulated box, covered with glass or plastic on the sun side to retard heat loss. In the collector, this heat transfers to a circulating liquid (such as water, oil or antifreeze) in which It is transferred to where it is used immediately or stored for later use. collector, solar. Any device for capturing solar energy. comfort zone. The limits to thermal comfort as defined by any combination of humidity and environmental temperature which gives thermal comfort, usually expressed In a graph with boundary (or limit) conditions shown, given certain other factors as constant, such as air movement, level of activity and metabolic condition among others. comfort zone, average. The range of effective temperatures over which the majority (50 per cent or more) of adults feels comfortable. comfort zone, extreme. The range of effective temperatures over which one or more adults feel comfortable. condensation. Process of changing a vapour into liquid by extracting heat; the process occurs when the vapour temperature falls below its dew-point temperature. conductance, thermal. Time rate of heat flow through a body (frequently per unit area) from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces under steady conditions. conduction (thermal). Transfer of heat from one portion of a medium to another without visible motion of the medium. conductivity (K). The quantity of heat that will flow through 1 sq m of material, 1 m thick. in 1 hour, when there is a temperature difference of 1 °C between its surfaces. conductivity, thermal. Time rate of heat flow through unit area and unit thickness of homogeneous material under steady conditions when a unit temperature gradient is maintained in the direction perpendicular to area. conductor, thermal. A material which readily transmits heat by means of conduction. convection. The transfer of heat from one part of a fluid (or gas) to another by flow of the fluid (or gas) from hotter parts to the colder (e.g., rising hot air). convector. An agency of convection. In heat transfer, a surface designed to transfer its heat to a surrounding fluid largely or wholly by convection. The heated fluid may be removed mechanically or by gravity connector). Such a surface may not be enclosed or concealed. cooling (evaporative). Heat exchange between air and water spray or wetted surface. The water assumes the wet-bulb temperature of the air. cooling cdl. An arrangement of pipe of tubing which transfers heat from air to refrigerator or cooling medium within the tube. cooling medium. Any substance the temperature of which Is such that it Is used, with or without change of state. to lower the temperature of other bodies or substances. degree day (dd) heating. An expression of a climatic heating requirement expressed by the difference In degrees C below the average outdoor temperature for each day and an established indoor temperature base of 18.3°C. The total number of degree days over the heating season indicates the relative severity of the winter in that area. dehumiditication. ( 1 ) Condensation of water vapour from air by cooling below the dew point. (2) Removal of water vapour from air by chemical or physical methods. dehumidifier. (1) An air cooler or washer used for lowering moisture content of the air passing through H. (2) An absorption or absorption device for removing moisture from air. dehumidifier, surface. An air-conditioning unit, designed primarily for cooling and dehumiditying air through the action of passing the air over wet cooling coils. dew point. Temperature at which gas containing a condensible vapour (e.g., moist air) becomes saturated and deposits liquid (dew). dew point temperature. The temperature at which condensation of water vapour In a space begins for a given state of humidity and pressure as the vapour temperature is reduced: corresponding to saturation (100 per cent relative humidity) for a given absolute humidity at constant pressure. diffuse radiation. Radiation that has been scattered by particles in the atmosphere, such as air molecules, dust and water vapour. direct radiation. Direct light from the sun, as opposed to diffuse sky radiation. double glaring. A form of glazing which incorporates two panes of glass separated by a vacuum, substantially stationary air or other gas. dry bulb temperature. Temperature of a gas or mixture of gases indicated by an accurate thermometer after correction for radiation. dwelling patterns. The way in which people use a dwelling during their normal daily lives. effective temperature. An American concept which corresponds to the British "equivalent temperature" and was developed by the ASHVE from 1923 onwards. It takes into consideration the temperature. humidity, and speed of movement of the air but does not consider radiation. See comfort zone. efficiency. In solar applications refers to the percentage of the solar energy incident on the face of a solar collector that ends up in use either for water heating or for space heating. emission factor, effective (E). The ratio of the thermal radiation emitted from the same area of a full emitted (black body) at the same temperature. emission factor, spectral (E). The emission factor at a given wave-length interval. emissivity. The capacity of a material to emit radiant energy. Emitance is the ratio of the total radiant flux emitted by a body to that emitted by an ideal black body at the same temperature. energy. Is defined as the capacity to perform work. All work is a consequence of a change of energy from one form to another. environmental temperature. The environmental temperature combines the effects of air temperature and the mean radiant temperature of surrounding surfaces. (This publication uses environmental temperature in preference to "effective temperature"). exfiltration. Air flow outward through a wall, leak membrane etc. frame construction. Any type of construction in which building is supported mainly by a frame, and not mainly by load- bearing walls. Brick-veneer houses, steel-framed buildings, and reinforced-concrete frame buildings all belong to this type. glass fibre (fibreglass, fiberglass). Mineral wool produced from molten glass. glasshouse effect. Refers to the characteristic tendency of some transparent materials such as glass to transmit shortwave radiation and block radiation of longer wavelengths, thus allowing the sun's energy to pass into a space (or glasshouse) but blocking the reradiation energy, causing the space to heat up. heat. Form of energy that Is transferred by virtue of a temperature difference. heat conductor. A material capable of readily conducting heat; opposite of an insulator or insulation. heat exchange. The process of using two streams of fluid for heating or cooling one or the other. heat exchanger. A device specifically designed to transfer heat between physically separated fluids. heat gain. An increase In the amount of heat contained in a space, resulting from direct solar radiation and the heat given off by people, lights, equipment, machinery and other sources. heat loss. A decrease in the amount of heat contained in a space, resulting from heat flow through walls, windows, roof and other building envelope components. heat pump, cooling and heating. A refrigerating system designed to utilize alternately or simultaneously the heat extracted at a low temperature and the heat rejected at a higher temperature for cooling and heating functions respectively. heat sink. A component (surface, volume or mass) that will conduct (and radiate) heat away from where the heat is being used or where it is not required. (Heat sinks into the heat sink.) heat transmission. Any time rate of heat flow; usually refers to conduction, convection, and radiation combined. heat transmission co-efficient. Anyone of a number of coefficients used In calculating heat transmission by conduction, convection. and radiation, through various materials and structures. humidity. Absolute humidity is the weight of moisture present in a unit volume of air. Relative humidity Is the ratio of absolute humidity to the amount of moisture which the same mass and volume of air could hold at a given temperature.
Infiltration. The uncontrolled movement of outdoor air into the interior of a building through cracks around windows and doors or in walls, roofs and floors. inorganic insulation materials. Thermal insulation material made from minerals such as rock, slag, glass and clay, which are processed by exfoliation, aeration or by the formation of fibres from the molten state. insulation, thermal. A material having a relatively high resistance to heat flow and used principally to retard heat flow. isotropic. Said of a medium, the physical properties of which do not vary with direction. joule. Is the international standard (Sl) unit for energy and it is denoted by the symbol "J". The joule is a very small unit, 3.6 million of them are equal to 1 kilowatt-hour. kilowalt-hour (kWh). Is the unit that is used for measuring the quantity of energy consumed per hour. For example, If a 1000-watt (single bar) electric radiator is swiched on for one hour it will consume 1 kWh of electrical energy; the same amount of energy would be required to light a
100 watt lamp for 10 hours. The unit of electrical energy that is recorded on domestic electricity meters is in kilowatt-hours. macroclimate. The general climate of a substantial part of the country or a region. mean radiant temperature (MRT). The temperature of a uniform black enclosure in which a solid body or occupant would exchange the same amount of radiant heat as in the existing non-uniform environment. microclimate. The physical state of an atmosphere close to a very small area of a region. mineral wool. Fibres normally made from molten glass, rock or slag, commonly supplied in the form of a bats, blanket a loose fill. See also rock wool, slag wool. night sky radiation. Under cool clear night sky conditions the earth and structures will radiate stored heat. The clear night sky acts as a heat sink If the air is cooler than the surrounding elements. non-renewable fuels. Fuels derived from fossil remains such as coal, oil, or gas and not capable of being replenished. Although wood is used as a fuel in some cases, and timber can be replaced, the rate of growth of timber is relatively slow compared with the rate at which It is consumed. overall thermal resistance. See R value. (Note. It is calculated as the reciprocal of the overall thermal resistance of an element. The sum of the surface resistance on each side of an element and the thermal resistances of the components including any cavities In the element.) passive system. A system of exploiting natural elements in a building order to modify the indoor climate without using special equipment. For example, the low angle of the winter sun can be allowed to enter through a window to heat up a room while in summer the sun, because it is directly overhead, can be readily excluded. power. The rate at which work is done or the rate at which energy is consumed. primary energy. Is derived from a source that has not undergone any processing that alters its nature before it is converted into useful energy. Oil or coal (although refined or modified) are not changed before they are used as a fuel for combustion. The heat from an oil or natural gas fire is a primary source of energy.
R value. Thermal resistance of the passage of heat provided by an element (roof, floor, wall). It is the reciprocal of the thermal transmittance of U value. radiant flux density. Radiant flux passing through unit area (unit, watt per square metre (W/m²)). (Note. The unit area usually considered is that normal to the radiant flux.) radiation. The direct transport of energy through space by means of electromagnetic waves. A process by which heat may be transferred from a source to a receiver without heating the intervening medium, or without the existence of a material medium. radiation draught. The draught of cold air that results from air against a window being cooled by radiation, and hence falling to the floor pulling more warm air in at the top to be chilled. reflectance. The ratio or percentage of the amount of light reflected by a surface to the amount incident. The remainder that is not reflected is either absorbed by the material or transmitted through H. reflective foil laminate. A type of reflective insulation defined in AS 1903 as a flexible sheet material, supplied In roll form. (Note. Reflective foil laminate usually comprises two outer layers of aluminium foil, forming an Integral part of the composite sheet material.) reflective Insulation. Thermal insulation having one or more surfaces of high reflection factor and low emission factor for low temperature (longwave) radiation, I.e., thermal radiation encountered within bulidings. (Notes. 1 . Reflective Insulation reduces radiant heat transfer across air spaces In a structure, and should therefore be used in conjunction with airspace. 2. Reflective insulation should not be confused with "solar reflective materials" which are intended to reflect shortwave radiation (solar radiation)). relative humidity. The ratio of the quantity of water vapour actually present in the air to that present at the same temperature in a water-saturated atmosphere. It is commonly expressed as a percentage. renewable fuels. Those fuels that can be used without any loss to the supply. These include solar energy (in all forms including wind and ocean waves which are derived from the effects of heat from the sun). and plants that grow rapidly and in large quantities (still largely in experimental stages). resistance (R). The reciprocal of conductance for a specific thickness of material. resistivity (r). The reciprocal of conductivity. rock wool. Mineral wool produced from molten rock or similar inorganic materials. root space. The space between a ceiling and roof covering. sarking membrane. A pliable membrane designed to collect and discharge any water that may penetrate a roof covering or wall cladding. secondary energy. Energy derived from a primary source. but which arrives at its point of use In a different form. Oil or coal (primary sources) are often used to create heat which is used to create steam to drive turbines that generate electricity. The electricity is wired to houses where it is converted back into heat or used to drive a labour-saving appliance. Electricity is a secondary source of energy. Gas made from coal is a secondary source of energy. skylight. A clear or translucent panel set into a roof to admit daylight into a building. solar heat gain. The amount of the sun's energy that enters a building can be measured in units represented by solar heat gain factor. This Is a measure of the amount of the sun's energy that is transmitted through a sheet of 3 mm thick glass. solar radiation. The electromagnetic radiation that is emitted from the sun. It affects temperatures inside buildings and is a significant influence on the internal climate. specific heat. The amount of heat required to increase the temperature by 1 K (unit. joule per kilogram Kelvin (j/kg.K)) stack effect. The tendency of air or gas in a duct or other vertical passage to rise when heated due to Its lower density in comparison with that of the surrounding air or gas. In buildings. the tendency towards displacement (caused by the difference in temperature) of internal heated air by unheated outside air due to the difference in density of the outside and inside air. sun position.
altitude. The angular distance above the horizon in the vertical plane. - azimuth. The angular distance east or west of the meridian in the horizontal plane. - meridian. The sun reaches its greatest altitude each day at solar noon when it crosses the meridian of the place where the observer is standing. temperature. Defined as the degree or intensity of heat of a body or atmosphere. The basic unit for measuring temperature value is the degree Celsius (°C). Temperature interval is measured in degrees Kelvin denoted by the international standard (Sl) symbol K. temperature, absolute. Temperature expressed in degrees Kelvin. temperature, dew point. The temperature at which a given sample of moist air will become saturated. without change in moisture content or atmospheric pressure and below which condensation will occur. temperature, dry bulb. The temperature of a gas or mixture of gases indicated by an accurate thermometer after correction for radiation. temperature, effective. The dry-bulb temperature of a black enclosure 50 per cent relative humidity in which a solid body or occupant would exchange the same heat by radiation convection. and evaporation as the existing non-uniform environment. thermal conductance. The quotient of the steady rate of heat flow normal to unit area of a planar element and the difference between the surface temperatures on either side of the element (unit. Watt per square metre Kelvin (W/m².K)). (Notes. 1. The value of thermal conductance is peculiar to the specific geometric configuration of the particular body or assembly. 2. Conductance differs from overall heat transfer co-efficient in that the temperatures used in the calculation differ. For conductance. the temperature Is the surface temperature of the faces of the element. For overall heat transfer co-efficient. it is the effective ambient temperature on either side of the element. Thus the overall heat transfer co-efficient (U) involves both the thermal conductance and the surface coefficients of the element.) thermal conductivity (k). The quantity of heat under steady-state conditions passing in unit time through unit area of a homogeneous material of infinite extent with flat and parallel faces and unit thickness when unit temperature difference is maintained between these faces (unit.
Watt per metre (W/m.K)). (Notes. 1. Materials may be considered as homogeneous when the value of thermal conductivity is not affected by variations in thickness or in area within the range normally used. 2. A thermal conductivity value should be identified with respect to: (a) mean temperature. since it may vary with temperature; (b) direction of heat flow and orientation of sample. since some materials are not isotropic with respect to heat flow: and (c) factors such as density, porosity. moisture content, fibre diameter and pore size.) thermal diffusivity (D). The quotient of the thermal conductivity and the thermal capacity per unit volume of a material (unit. square metre per second (m²/s)). thermal insulation. A material or assembly of materials used to provide resistance to heat flow. thermal isolation. The ability to isolate a body from the thermal affects of the climate. thermal mass. The amount of potential heat storage capacity available in a given assembly or system. Drum walls, concrete floors and adobe walls are examples of thermal mass. thermal resistance (R). The reciprocal of "thermal conductance" (unit. square metre Kelvin per watt (m².K/W)). (Notes. 1. Thermal resistance may be conceptualized as the time for unit energy to pass through unit area of a building component having unit temperature difference between its two surfaces. 2. When heat passes in succession through the components of an element the resistances can be added together and the total thus obtained is the resistance of the element.) thermal resistivity (1/k). The reciprocal of "thermal conductivity" (unit: metre Kelvin per watt (m.K/W)). thermal transmission. The amount of heat flowing per unit time under conditions prevailing at that time (unit. watt (W)). thermosyphon. The method establishing circulation of a liquid by using the slight difference In density of the hot and the cool portions of the liquid. transmission factor (T). The ratio of the radiant flux transmitted by a body to that incident upon the body. (Notes. 1. Transmission factor varies with the wavelength of the incident radiation. 2. In the case of transparent and translucent materials, such as glass, the transmission factor will vary with thickness. 3. In the case of opaque materials, the transmission factor is zero.)
U value (coefficient of heat transfer). A figure determined by experiment for a certain situation which tells how many watts per hour will pass through one square metre of the wall when the temperature difference of the air between both sides is 1 °C. It is the amount of heat transferred due to temperature differences in the air on both sides of the element. vapour. A gas, particularly one near to equilibrium with the liquid phase of the substance and which does not follow the gas laws. vapour barrier. A component used to restrict the transmission of vapour (general water vapour). ventilations. The process of supplying or removing air by natural or mechanical means to or from any space. Such air may or may not have been conditioned. volumetric heat capacity. The amount of energy (in joules) that a volume of material (m³) can store with a 1°C rise in its temperature. watt. Is the international standard (Sl) unit for power and it is denoted by the symbol "W". One watt represents one joule per second.
W/m²K. Watts per square metre Kelvin is the international standard unit of thermodynamic temperature. The temperature interval of 1 Kelvin (K) equals of 1 °Celsius (C). wind rose. A diagram that Indicates the relative direction, frequency and mean velocity of winds for a given location.