A system for heating and/or cooling a building using solar equipment such as solar panels, heat exchangers, and the reticulation of water or other liquids or gases to transfer heat between the interior of the building and its environment.  

Shading to windows or other building elements which may be adjusted, either mechanically or manually, according to the requirements of the climate and/or the position of the sun.

The rate at which the internal air in a building is exchanged with the exterior air, whether naturally (see infiltration and ventilation) or artificially (see exhaust fan). In typical Australian domestic construction the air change rate has been measured at up to 12 air changes per hour. This clearly has implications, especially for winter comfort and for the cost of heating, as the air takes heat with it! A level of 1/2 to 1 air change per hour is considered acceptable; a very low rate can be dangerous, due to the accumulation of bacteria, radon gas and other noxious factors. (See sick building syndrome)

Mechanical means of conditioning the air in a building in terms of its temperature, its relative humidity and its cleanliness/purity.

Movement of the air in an interior space; gives some relief from high temperatures due to the evaporation of moisture from the skin, which removes latent heat from the body.

The space between one part of a building element and another (eg in a wall or roof assembly).

The movement of heat through a building element due to the difference in air temperature between one side and the other.

American Society of Heating, Air-conditioning and Refrigeration Engineers (ASHRAE); carries out research and publishes much useful data on thermal performance.

A house which provides adequate conditions for civilised life (whatever that may be!) but is independent of the infrastructure of electricity, gas and water supply and sewerage.; generally such a house runs on solar and/or wind energy, and is designed on ‘passive solar design’ principles, and is equipped with highly efficient appliances (if any). Clearly there are questions of expectations involved here.

The ‘definition’ of Autumn depends on the context. In temperate places with deciduous trees it is the season following summer during which the leaves turn yellow, red and brown and fall (it is known as Fall in Canada and the USA). (Tropical climates do not have an Autumn: see dry season, wet season and monsoon). The Equinox marks the beginning of autumn (March 21/22 in the Southern Hemisphere, and June 21/22 in the Northern Hemisphere).

The highest point reached by the sun in its path along the ecliptic (ie at solar noon).

The ability of a given substance to emit radiation when heated is proportional to its ability to absorb radiation. A black body is a theoretical body with properties such that it absorbs all the radiant energy falling on it, reflecting and transmitting none, and emits radiation perfectly freely. 

1) In scientific parlance, any object made of some solid material; 

2) The human body.

Part of a building such as a wall (assembly), the glass of a window, a floor slab and its foundations, a roof/ceiling assembly.

The external building fabric, separating the interior from the exterior; ie the walls (including windows and external doors), the roof, and the floor. 

The constructional elements of a building - walls, windows, floors, roof. 

Insulation which resists conduction and convection of heat due to its non-conductive material and entrapped gas or air. Examples are fibreglass batts and blanket, cork, urea-formaldehyde and poly-styrene. Each type of bulk insulation has its advantages and its disadvantages; some may be flammable, or may emit toxic fumes if they catch fire. 

a rotating fan installed on the ceiling, which does not remove or change the air in a space, but can improve summer comfort by means of air movement. (Compare with exhaust fan.) Not advisable with a ceiling height less than 3 metres.

Temperature scale which divides into 100 parts (degrees) the interval between the freezing point of water (strictly the temperature of a mixture of pure ice, water and water vapour in mutual equilibrium) and the boiling point of water at 1 atmosphere of pressure. 

The energy liberated in a chemical reaction, such as burning. 

Green pigments involved in photosynthesis. Chlorophyll a is the primary photosynthetic pigment in all those organisms that release oxygen ie all plants and all algae.

Scientifically speaking: the statistical ensemble of atmospheric conditions characteristic of a particular location over a suitably long period (eg 30 years) including relevant parameters such as mean and extreme values, measures of variability, and descriptions of systematic seasonal variations. Aspects considered include temperature, humidity, rainfall, solar radiation, cloud, wind, and atmospheric pressure. (Compare with weather).

A measure of the amount of clothing worn by the inhabitants of a building, used in research to assess levels of thermal comfort.

The proportion of the visible sky covered by cloud: measured in octals (eighths).

The colour of the surface of an element has a significant effect on its thermal behaviour under (solar) radiation. Highly reflective surfaces (eg polished aluminium) allow the transmission of very little heat, while dark surfaces absorb a large proportion of the radiation that falls on them. White surfaces reflect a high proportion at visible frequencies (but much less at low frequencies). Black surfaces absorb nearly all incident (incoming) wavelengths. Coloured surfaces, even those which appear light in colour, behave more like black than white surfaces. (See reflectivity, emissivity).

A type of toilet which converts the waste into a useable compost within 6 months. No water is used; the waste falls into a chamber below the toilet and is mixed with sawdust and lime and kept aerated (separate of course from the bathroom!)  Generally two chambers are used to ensure time for natural heat and bacterial action in the chamber not in use to kill pathogens.

The change of state of the vapour in the air to water, on a cold surface such as a window pane or an uninsulated wall or ceiling (see Dew Point).

The transfer of heat through a medium by direct contact.

A type of climate found in continental areas not subject to maritime influences. In temperate zones these are characterised by pronounced extremes between summer and winter. The increase in temperature differences between day and night, and between summer and winter is caused by the difference in the thermal capacities of water and land: the land heats up and cools down approximately five times more quickly than the sea.

the transfer of heat through a fluid medium (eg air or water) by movement of parts of that medium, in particular by the rising of heated (and thus less dense) parts of the medium.

A calculation of the value of an investment, eg proposed thermal improvement to a building, in relation to its cost;  such calculations must compare like with like, eg the total current cost against the current equivalent value of any estimated future savings, or the equivalent annual cost against the estimated annual savings (eg by calculating the discounted cash flow). 

Ventilation, whether natural (winds) or mechanically induced (fans), which takes (cool) air through a building, generally with the aim of cooling it and/or its inhabitants.

A measure (in percentage) of the partial shading effect on a surface caused by for instance trees, shrubs or vines over a pergola.

Design of the jointing and fixing etc. of building materials and elements.

The temperature at or below which condensation will occur on a surface by condensing out of a gas (eg air) at a certain relative humidity (see Psychrometric Chart).

The portion of solar radiation scattered (up to about 25% of the direct radiation); it is non-directional.

That portion of solar radiation which is not scattered on its path from sun to earth; it is directional, and at ground level on a clear day is about 1000 W/m² on a surface perpendicular to its rays. 

A method of calculating costs or returns on investments which takes into account the changes on the value of money over time eg due to inflation, and the availability and rate of interest, so as to relate all expenditure and income at the same point in time; used to assess the cost/benefit ratio of thermal improvements.

The temperature difference (‘swing’) over a day - between daily minimum and daily maximum;  greater in inland regions than near the coast, due to the greater thermal inertia of the sea than that of the land.

Glazing whose U-value is reduced from the level of standard single glazing by the installation of two panes. ‘Evacuated’ double glazing is factory-constructed hermetically sealed with a near vacuum between the panes; if air is allowed between the panes, condensation may occur, so glazing should be constructed to allow access to the air space. (In higher latitudes of the Northern Hemisphere, triple glazing is common).

The difference in temperature across a building element which causes heat flow from the hotter to the colder side.

The temperature of still air measured by a standard thermometer protected from sources of radiation.

In the tropics, the season of minimal rain

An enclosed channel, usually horizontal or vertical, and larger than a pipe, provided to carry air, pipework or service cables etc.

The scientific study of the interrelations between living organisms and their environment, including both the physical and biotic factors, and emphasising both inter-species and intra-species relations; more specifically and more narrowly, the scientific study of the distribution and abundance of living organisms (ie exactly where they occur, and precisely how many there are), and any regular or irregular variations in distribution and abundance, followed by explanation of these phenomena in terms of the physical and biotic factors at work in the environment. 

A measure of how well a device or system works.

A measure of how well a device or system works in relation to the input of resources (eg energy) required.

The ratio of the heat emitted from a surface to that emitted under the same conditions by a ‘Black Body’.

The energy required in the industrial or other processes used to manufaacture building materials etc.

The two days of the year when day and night are of equal length,  21 March and 21 September.

Environmentally Sustainable Design.

A system of cooling produced by utilising the latent heat of vaporisation of water.

A fan which exhausts air (with its smells and water vapour) through a wall, window or ceiling from a space or building; often multi-speed. It is advisable that a ceiling exhaust fan be ducted through the roof space to the external air. (Compare with ceiling fan).

Shading systems which cannot be moved in relation to the position of the sun.

The capacity of a structure to resist bending. Beams have greater flexural strength when fixed with their larger cross-sectional dimension vertical.

Flow - generally of energy (eg heat or light).

Light-weight concrete which has had entrained air added by foaming after  pouring.

Energy obtained from the intensely hot molten magma deep in the earth, usually utilised by means of electricity generation by steam from underground sources.

Uncomfortable or disabling visual sensation caused by excessive and uncontrolled brightness.

The generic term for windows and the glass installed in them (see double glazing).

The theory - now generally accepted - that the average temperature of the earth is likely to rise due to a change in the heat balance of the earth and its atmosphere provided by the ‘greenhouse effect’ 1), as a result of human energy consumption and pollution, with unpredictable (so far) effects on the climatic and ecological balance of the earth.

Temperature measured by a thermometer with the bulb surrounded by a black globe of diameter  15.2cm (6 inch); the temperature thus measured combines air and radiant temperatures.

1)  the fact that glass and other transparent / translucent buildingmaterials, and the earth’s atmosphere, are relatively transparent to the high frequency radiation of the sun’s rays, while being relatively opaque to the low frequency radiation (heat) given off by building materials, contents and inhabitants, etc. and the earth’s surface in general; 

2)  the global warming effect that climate researchers warn of in relation to the pollution of the earth’s atmosphere by CO₂ and NOx gases etc., and thus its increased opacity to low frequency radiation.

A form of energy.

Glass incorporating metal particles which absorb solar radiation passing through the glazing; a proportion of this heat is then re-radiated outwards. The total heat transfer through the glass is thus reduced compared with standard glazing. As its operation depends on absorbing the incident radiation, heat-reflecting glass itself heats up, and some of this heat re-radiated into the internal space, which can cause discomfort to people near windows.

A part of a building element or assembly which due to its high conductivity transfers heat rapidly through the element. Also known as Thermal Bridge. 

The transmission of heat through a medium such as a building material or building element.

Heat input to the interior of a building eg from the sun through windows, from equipment such as lights and computers, and from inhabitants’ metabolic function (see useful heat gain).

The passage of heat through building elements from interior to exterior.

Heating/cooling equipment which operates by taking heat at a low temperature from a medium such as water or air, and transferring it at a higher temperature by means of a condenser;  for cooling, from inside a building to outside, for heating, vice versa.

Glass with a surface film of transparent reflective aluminium which reflects a percentage of the incident radiation; different grades reflect given percentages of total radiation, from 20% to 85%. It can be useful for privacy as well as for heat control; it should be remembered that from the lit side such glass appears to be a mirror, so at night can give a false sense of security while giving a clear view from outside. (As it does not depend on absorbing the incident radiation heat-reflecting glass is more effective than heat-absorbing glass).

The capacity of high thermal mass materials to store energy (heat) to reduce the impact of heat inputs (eg the sun) on internal temperatures in a building in the hot season (see ‘Difference between temperature and heat’).

The capacity of high thermal mass materials to store energy (heat), in particular solar energy through windows, to later re-radiate into the building; generally utilised during winter to sustain a comfortable internal temperature,  eg overnight. Also known as Thermal Storage.

Masonry or brick cavity construction, generally on a concrete slab, which provides thermal storage capacity for passive solar design. 

Radiation above approx. 5 micrometres (including the visible spectrum and solar radiation): both polished aluminium and white paint are good reflectors at these frequencies.

The energy balance attained by a healthy (human) body between its deep body temperature, its skin temperature and the temperature of its ambient environment (Also Homeostatic Balance).

The evaporation and condensation of water on a global scale. In simple terms evaporation from bodies of water on the earth’s surface (rivers, lakes and the sea) leads to the formation of clouds which results in precipation, filling the bodies of water. Deforestation, pollution and global warming are likely to change the patterns of precipitation (type, magnitude, periodicity and location) and cause serious problems for eco-systems and human settlements, activities and economies.

The pressure at a point in a liquid, caused by the height above that point of a column or storage tank of liquid connected directly to it (as in a header tank).

Extreme over-heating of the human body above normal temperature.

Extreme cooling of the human body below normal temperature.

The vertical angle of a sloping surface such as a roof, measured from the horizontal.

A panel eg of brickwork forming a wall between columns, not forming part of the supporting structure of the building.

The air changes in a building between interior and exterior air that take place ‘involuntarily’ through cracks and openings (eg under doors, around window and door openings), and in former times up chimneys. In common parlance they are called draughts when not wanted. Across the tropical zones building construction allows a relatively high level of infiltration compared for instance with Scandinavian building construction.

Materials or combinations of materials used in buildings (eg in roofs and walls) to reduce unwanted heat transfer from one side of a building element to another.

Strength (eg of solar radiation). 

A measure of the rate at which internal building surfaces absorb heat;  measured in W/m².K 

A Joule (J) is a unit of energy (a Watt.sec.)

A temperature scale in which the value of a degree is the same as the Celsius scale, but whose zero point is -273.16^oC, generally rounded to -273^oC. This temperature (absolute zero) is the temperature at which in theory the molecules of an ideal gas would cease to move. (In practice all gases, on cooling, liquefy or solidify before this temperature is reached).

kWh kiloWatt-hour;  1000 Watts of energy over a period of 1 hour.

The length of time (time lag) required for a ‘driving temperature ‘to cause heat flow through a building element;  used in calculations of ‘transient heat  flow’.  Ranges from less than 1/2 hour in lightweight materials to over 36 hours for concrete slabs-on-ground.

The heat added to or removed from a body in the change of state from solid to liquid or liquid to gas (added) or vice versa, (removed), not causing a change of temperature;  cf sensible heat, which causes a change in temperature.

Concrete which has been made less dense

Construction in stud frame or brick veneer, generally with a suspended timber floor, providing little thermal storage capacity.

Formwork which is left in place permanently, often to provide the required finished surface.

Can be glass, used as windows (fixed or adjustable), or in aluminium or steel, used for shading. Louvres used for shading should be used vertically to east and west, and horizontally on the north and south. 

Low-frequency / long-wavelength radiation (above 5 micrometres); the range of the heat flow in the walls and roofs of buildings. White paint is a good reflector of visible light, but a poor reflector of room temperature radiation. 

A type of climate found in coastal areas subject to maritime influences, and characterised by less pronounced extremes between summer and winter; also relatively high rainfall and humidity. The reduction in temperature difference between day and night and between summer and winter is caused by the difference in the thermal capacities of water and land: the sea heats up and cools down approximately five times more slowly than the land.

Technical term for average.

The area-weighted average of the temperatures of surrounding surfaces.

Ventilation by means of fans, with or without ducts, which moves air from one place to another wihtout othrewise changing its characteristics (compare with air-conditioning, which changes temperature, humidity and purity of the air).

The physical functioning of the (human) body which causes it to give off heat (at the rate of about 100W).

The study of the earth’s atmosphere in its relation to weather and climate.

The climatic conditions in a small region or locality, affected by such factors as slope, orientation, hills, rivers, forests buildings.

Small hydroelectric systems, generally exploioting streams and small pressure differences to provide low voltage power for domestivc use.

Having compatible dimensions so that combinations are easily constructed (of elements of a building).

Heavy rains in coastal tropical zones.

Energy from burning such resources as petroleum and coal, laid down over millions of years from chemical reactions which once used will not be renewed.

Perpendicular (at right angles).

The measure of sky cloud cover used in calculations of the thermal performance of a building.

The direction a building or portion of a building faces in relation to the cardinal points (N, S, E and W) and to the sun.

Design of buildings to exploit the characteristics and performance of the building fabric and the management of the building to achieve human comfort conditions without mechanical assistance.

Any disease-producing substance or (micro-) organism, eg a bacterium, virus or parasite.

A construction of posts, beams and battens and/or wires, generally attached to a building, to support creepers and/or shade-cloth to shade windows or an outdoor area.

The term “Permaculture” was coined (from permanent and agriculture) by the Australian ecologist Bill Mollison to describe an approach to the development of ecologically sustainable human settlements — including dwellings and agricultural and other production — which works with nature rather than against it, and emulates the complexity of natural eco-systems.

The use of energy from light to drive chemical reactions; the most common use of the term is to describe the use in plants of solar radiation to reduce carbon dioxide to carbohydrates coupled with the oxidation of water to free oxygen. This is the mechanism that converts the energy of solar radiation to chemical energy, which can then be used by animals (food) and people (eg food, fodder, firewood and petroleum). (See chlorophyll).

A photoelectric cell made from silicon which collects photons from solar radiation and acts as a source of electromagnetic force, and thus converts solar energy into useable electrical energy with a reasonable degree of efficiency (generally at low voltages). They can be used in conjunction with batteries to provide power 24-hours a day.

Silicon cells connected in arrays to provide electric current directly.

The effect that causes air to rise in a chimney or duct due to wind passing over the opening at the top of the chimney, thus reducing the pressure in the chimney.

Elements of a structure held in place and/or given flexural strength by a tension force added by means of tension steel (reinforcement) after construction, such as pre-fabricated concrete beams or slabs,  or terra cotta panels.

The moisture that falls on the earth’s surface from clouds; it may be in the form of rain, snow, hail and sleet.

A chart correlating the physical properties of air, such as wet- and dry-bulb temperatures, dew point, relative humidity and enthalpy.

Electro-magnetic waves — heat, light and electricity;  in the context of thermal performance, high frequency (the rays of the sun), and low frequency (heat given off by bodies (both types) and materials). 

Any heater depending for its operation on radiation rather than convection.

A layer of reflective foil insulation used as a barrier to radiant heat and as a condensation barrier.

The ratio of the thermal radiation reflected from a surface to that falling on it.

The ratio of the vapour pressure in the air at a given temperature and pressure to the vapour pressure of saturated air at the same temperature and pressure.

Energy from renewable sources, all except tidal power ultimately derived from solar energy (ie the sources of such energy are renewable from the point of view of the earth, but do not contradict the First Law of Thermodynamics!). Examples are the direct use of solar energy as heat (eg solar hot water services), arrays of photovoltaic cells which convert solar radiation directly to electricity; or the indirect use of wind power with wind-mills of various types, or hydroelectric systems which uses the head (pressure difference due to height) of stored water to operate a turbine generator. Firewood is often described as a renewable energy source, on the grounds that  ‘trees grow again’, but this ignores the ecological damage done in commercial forestry. After large-scale felling, trees may be replaced, but the complex eco-system does not return.

An approach based on practice rather than theory.

Air containing the maximum amount of water vapour possible at a give temperature and pressure.

Cooling summer breezes coming off the sea; useful for thermal relief in coastal areas.

The notion of season is significantly context-dependent. In temperate zones of the world, four distinct seasons are evident  (See Summer, Autumn, Winter and Spring). Tropical zones generally have two seasons (Dry and Wet). Some tropical locations have a third season, the Monsoon Season.

In simple terms, it states that warm objects lose heat to their surroundings unless something is done to prevent this. 

Method for treating sewage from a single dwelling; the effluent (faeces, urine and flushing water) is discharged to a tank in which it is acted on by anaerobic bacteria in the absence of oxygen; the effluent is then discharged through effluent lines dispersed over a large area. 

A phenomenon whereby people experience ill health linked to spending time in a particular building but where no particular cause can be pinpointed.

Silica, a non-metallic element, symbol Si, is the second most abundant element, silicates being the chief comstituents of many rocks, clays and soils. Silicon is manufactured by reducing silica with with carbon in an electric furnace, and is used in glass and in making certain alloys. It has super-conducting properties and is used in a large range of electronic components, including photovoltaic cells.

A variable used to calculate a buildings cooling load and to determine heat gain through exterior surfaces.

The term is generally used to refer to the direct use of the energy of solar radiation.However, it should be remembered that it is the sun, combined with the rotation of the earth, which causes the winds used by wind-mills, and the hydrological cycle which causes the rain and thus the possibility of exploiting hydro-electric power generation.

The time at which the sun reaches the azimuth each day. Clock Time may vary considerably from Solar Time. 

Radiation from the sun, whether direct or diffuse(d), at wavelengths varying from ultra-violet through visible to infra-red (0.3 - 3.6mm); it reaches the earth at an intensity of about 1000W/m² on a surface normal to its rays.

The two moments in the year when the Sun's apparent path is farthest north or south relative to the Earth's Equator.

The capacity of a body to contain heat; measured in J/Kg.

The season following Winter during which the weather warms up and bare branches and bulbs sprout. (Tropical climates do not have a Spring: see dry season, wet season and monsoon).

Heat flow through a building element or material under the simplifying assumption that the temperatures on each side of the element remain constant;  this does not normally occur in the real world, but may be assumed for approximate calculations under appropriate conditions.

The warmest season of the year. (Tropical climates do not strictly have a Summer: see dry season, wet season and monsoon).

See Temperature Swing.

An intimate partnership between two organisms in which the mutual advantages normally outweigh the disadvantages.

A climate zone found in the middle latitudes, which span between the tropics and the polar regions of Earth.

The temperature difference from bottom to top of a volume of air or water which causes convection to occur.

Daily (diurnal) temperature range from maximum to minimum and back -measured in terms of variation from the mean (average).

See Heat Bridge.

The thermal or heat capacity of a body is the quantity of heat required to raise the temperature of a body by one degree.

By analogy with mechanics, a term to describe the dampening effect on temperature swings of thermal mass.

(Usually refers to high) thermal capacity in building materials. 

The effectiveness (and efficiency) or otherwise of a building in maintaining comfortable thermal conditions for its inhabitants.

The combined resistance (R) offered by a building element or assembly to heat transfer, including the effect of air spaces, reflectivity of surfaces and their condition; measured in m².K/W. Also known as the R-Value. It is the reciprocal of the Transmission Coefficient (ie 1/U-Value).

The rate at which heat is transmitted through a building element or assembly (U), combining radiation, conduction and convection, and including the effect of air spaces, and the reflectivity of surfaces and their condition; measured in W/m².K. Also known as the U-Value. It is the reciprocal of Thermal Resistance (ie 1/R-Value).

A continuously recording thermometer. The temperature recording is usually is made by the movement of pen connected to a bi-metallic spiral on graph paper on a rotating drum.

Publicity material and technical / construction / installation data provided by manufacturers and suppliers of building elements and materials. 

A measure of the heat flow to the interior of a building element due to variations in the external ‘driving’ temperature;  measured in  W/m².K

The usual conditions under which heat flows through building materials and elements with temperatures on both sides continually changing.

A material that allows light to pass through, allowing objects behind to be clearly seen.

A wall used to absorb thermal energy from incident sunlight and covered. It can be used to heat a space in cooler climates, or regulate temperatures in warm climates. Also known as a Mass Walls, Solar Wall, or Thermal Storage Wall.

A climatic zone largely falling in the equatorial or tropical zone. It is generally characterised by relatively warm and consistent temperatures throughout the year.

The solar heat gain through a window less the amount of heat lost through that window due to the temperature difference (inside to outside), and the Thermal Transmission Coefficient (U) of the glass. 

The intentional admission of air into, out of and/or through a building; at times desirable in summer, usually undesirable in winter.

The value of an Electromagnetic Force (EMF) or potential difference expressed in volts.

The temperature measured by a thermometer with its bulb covered by a wetted wick, showing the effect on the measured temperature of moisture in still air;  wet- and dry-bulb temperatures can be correlated on a psychrometric chart to determine relative humidity.

The season of the monsoon in the tropics.

A measure used to indicate the rate of heat loss from skin when exposed to  air (see also Heat Index).

The use of wind turbines to generate electricity. Also known as Wind Energy.

This is the coldest part of the year, and begins at the Winter Solstice (December 21st in the Northern Hemisphere, and June 21st in the Southern Hemisphere). Tropical climates do not strictly have a Winter, but have Dry and Wet Seasons.

Dimensioned, graphical information used to price, fabricate, assemble, install or construct a project.

The highest point reached by the sun in the sky over the year — at solar noon at the Equinox.

The allocation of areas in a dwelling (or areas of a farm or garden, or in urban planning districts in a city) in accordance to some principle of planning. An important aspect of Permaculture design, in locating the various functional areas of a farm or garden around the homestead, according to distance, access, orientation to sun and wind, soil, topography etc.. In climatic design of buildings and precincts, locating areas for certain activities together in appropriate locations in relation to aspectsof the micro-climate, in particular the path of the sun, and the directions of prevailing winds.