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A simplified explanation of references used in the text divided into the following eight headings. Use the Index for page references. This is similar to the Glossary used in The Lit Environment, which will enable the two books to be used together.










Adaptation The human eye can adapt to widely differeing levels of light, but not at the same time. When entering a darkened space from a brightly lit space, the eye needs time to adapt, to the general lighting conditions; this is known as 'adaptation'.

Clarity Clearness, unambiguous.

Contrast The visual difference between the colour or brightness of two surfaces when seen together. Too high a contrast can be the cause of glare.

Modelling The modelling of an object derives from the direction and intensity of the light falling upon its surfaces, which provides the shadow patterns leading to an understanding of its form.

Perception Receiving impressions of one's environment primarily by means of vision, but also one's other senses; providing a totality of experience.

Quality, a degree of excellence The 'quality' of a lighting design derives from a series of different elements, the most important of which is 'unity',

1 Phillips, D. (2002) Lighting Modern buildings, Architectural Press.

but which also includes aspects such as modelling, variety, colour and clarity.

Unity The quality or impression of being a single entity or whole; this can be applied equally to a small or large complex, the word 'holism' is often used in its place.

Variety The quality of change over time in brightness, contrast and appearance of a space, or series of spaces.

Virtual image An image of a subject or lit space formed in a computer, which can be used to provide a visual impression of the lighting design in order to explain a proposal.

Visual acuity A measure of the eye's ability to discern detail.

Visual task/task light The visual element of doing a job of work, and any local or concentrated light fitting placed to improve visibility.


Artificial sky A research tool in the form of a ''light box'' where levels of light may be measured in architectural models placed within. Sophisticated artificial skies exist whereby the light can be varied to replicate the exterior light and sun paths at different seasons and climates. The opportunity exists for miniature photography of interiors, and visual inspection of the interior by the architect.

Average daylight factor An analysis of the Daylight Factors in an interior to gain an overall or average view of the daylighting in a space.

Bilateral daylight Daylight from both sides of a building.

Daylight The light received from the sun and the sky, which varies throughout the day, as modified by the seasons and the weather.

Daylight effective depth The distance from a window which allows daylight to penetrate to achieve a desired Daylight Factor.

Daylight factor (DF) The ratio of the light received at a point within a building, expressed as a percentage of that available externally. Since daylight varies continually the amount of light from a given DF is not a finite figure, but gives a good indication of the level of daylight available.

Daylight linking Controls which vary the level of artificial light inside a building, relating this to the available daylight.

Electrochromic glass Glass designed to respond indirectly to an electric current which alters its transmission value

Georgian window The standard sash window for domestic use in the eighteenth century in England, combining clear daylight, with view and ventilation.

Heliostats A system of mirrors placed at roof level which can be energised to track the sun, and redirect it into a building.

Indirect daylighting Similar to indirect artificial lighting, whereby the light from ''windows'' is concealed from the view of the building occu pants giving light to surfaces and objects within a space. This has particular relevance in churches.

Innovative daylighting Methods of daylight admission to a building which take advantage of a new technology: examples being Light Shelves, Light Pipes, or heliostates etc.

Interactive window A prototype window design, combining the requirements of daylighting and view, with those of solar control, and ventilation, thermal and sound insulation and the elimination of glare.

Light penetration See daylight effective depth.

Light pipes A form of rooflight associates with mirror finished ducts which direct natural light and sometimes ventilation into lower floors of the building.

Light shelves A horizontal construction at the window designed to reflect light to the ceiling, to assist in increasing the daylight penetration into the room

Low emissivity glass Glass where the radiating power of heat or light is reduced

No sky-line The demarkation line within a building where, due to external obstruction and window configuration, no view of the sky is visible.

Obstruction/view The diminution of available light and view by other buildings at a distance. View is an important environmental aspect of daylight, which may be impaired by obstruction, but can sometimes be overcome by attention to orientation.

Orientation The geographical relationship of a proposed building to its site, enabling a strategic view to be gained of the possible daylighting design.

Physical modelling The use of architectural models to provide a means of calculating the daylight factors of a proposed building design. These can be placed in an artificial sky or used externally. Physical modelling has been found to mimic methods of computer calculation sufficiently accurately with the added advantage of providing a visual impression of the interior to the architect.

Photochromic glass Glass responding directly, to an environment stimulus such as heat or light, which alters its transmission value

Prismatic panels Panels formed to alter the path of light, so as to redirect it, either to cut out glare, or to introduce light for useful purposes

Rights of light Legislation which allows a building owner to preserve the amount of natural light his building enjoys; likewise he must ensure that his building does not obstruct the daylight enjoyed by his neighbour.

Shading/briese soleil The means adopted to prevent the deleterious effects of solar gain from southern exposures; these may be external structural louvres attached to the face of the building or forms of heliosc-reen blind.

Sky glare The unacceptable contrast between the view of the sky outside, and the interior surfaces.

Skylight The light received from the whole vault of the sky as modified by the weather and time of day, ignoring sunlight.

Solar gain Heat derived from the sun; whilst generally therapeutic, it may require control by forms of blind, louvre or solar glass.

Solar glass Glass designed to reflect a percentage of direct heat (infra red) from the sun.

Solar panels Panels applied mostly to south facing facades of buildings designed to generate electricity from the sun. This can be used for heating water or for lighting.

Solar shading The mechanical means by louvre, blind or special glazing, to eliminate glare from the sun. External means are the most efficient, but can suffer from long term maintenance.

Sunlight The light received directly from the sun, as opposed to that derived from the sky.

Sunpath The sun's orbit. As the earth travels around the sun, variations occur both throughout the day and the seasons; these changes in position are known as the 'Sunpath'. This can be accurately predicted.

Sustainability Applied to development which meets the needs of the present, and is at least as valuable to future generations, as the value of the environmental exploitation that results. This can be applied to the concept of nett zero energy demand.

View The scene beyond a window which can be enjoyed from within a space. The importance of this should not be underestimated.

Window 'Wind-eyes' take many forms, to provide daylight to an interior.


Arc light The first form of electric light derived by passing an electric current between two electrodes. Developed by Sir Humphery Davy in 1809.

Candles Candles are made by moulding wax or other flammable material around a wick, which sustains a flame to give light. Modern candles are clean, do not 'gutter', and provide light of a particular quality suitable for social occasions. There have been many light sources which attempt to imitate the quality of 'candle light'; most fail completely, while one or two later versions achieve some success.

Electric light The development by Edison and Swan of the 'incandescent' lamp in the nineteenth century and the arc lamp, providing the foundation of all modern forms of light derived from electricity.

Electric light sources These lamps are described in detail in Chapter 5, and are listed here.

Incandescent sources tungsten filament tungsten halogen low voltage tungsten halogen

Discharge sources cold cathode (fluorescent)

mercury fluorescent (high and low pressure)

low pressure sodium high pressure sodium high pressure mercury metal halide (inc. ceramic arc)

Fluorescent lamps halophosphor - tubular fluorescent triphosphor compact fluorescent induction lamps

Fibre optics (remote source) At its simplest, it is the transfer from a light source placed in one position to light emitted in another, by means of glass fibre or polymer strands.

Fluorescent phosphors The internal coatings on surfaces of mercury discharge lamps which produce 'visible' light when excited by the ultraviolet rays emitted by the discharge. The phosphors determine the colour of the visible light.

Gaslight The light derived from burning coal gas, developed in the late eighteenth century, and widely used during the nineteenth century both for domestic and industrial use.

Oil lamps These together with firelight are the earliest forms of artificial light source, the oil being derived from animals, birds or fish. Hollowed out stone dishes and later clay pots were used with some form of wick. Oil lamps survived until the nineteenth century with the development of the 'Argand' lamp.


Angle of separation The angle between the line of sight and the light fitting. The smaller this is, the more likely the light will be glaring.

Brightness The subjective appearance of a lit surface; dependent upon the luminance of the surface and a person's adaptation.

Bulk lamp replacement The replacement 'en masse' of the lamps in a lighting system when it is calculated that a percentage of the lamps will fail, and that the light output of the system will fall below the design level.

Colour We accept that we only see true colour under daylight, despite the fact that this varies considerably throughout the day. All artificial sources distort colour in one way or another.

Colour renderng A comparison between the colour appearance of a surface under natural light and that from an artificial source.

Efficiency/efficacy The ratio of the light output from the lamp, toe nergy consumed in lumens/watt.

Flicker The rapid variation in light from discharge sources due to the 50 Hz mains supply, which can cause unpleasant sensations. With the development of high frequency gear the problem is overcome.

Glare/reflected glare The most important 'negative' aspect of quality. There are two types of glare, 'discomfort and disability.' Both types are the result of too great a contrast. Glare may result from both daylighting or artificial lighting, either directly or by reflection and must be avoided at the design stage.

Illumination level The amount of light falling on a surface expressed in engineering terms as lumens per square metre (or Lux) and known as 'illuminance'.

Intensity Refers to the power of a light source to emit light in a given direction.

Light fitting/luminaire The housing for the light source which is used to distribute the light. While the technical word is 'luminaire,' the more descriptive 'light fitting' is still widely used. The 'housing' provides the support, electrical connection and suitable optical control.

Luminance Light emitted or reflected from a surface in a particular direction; the result of the illumination level and the reflectance.

Lux The measure of 'illumination level' (illuminance) in lumen/sq.m. The Foot Candle is used in the USA, meaning 1 lumen per square foot or 10.76 Lux.

Maintenance factor The factor applied to the initial illumination level, to take account of dirst accumulation and fall off in light output from the lamp, when calculating the level of useful light.

Reflectance The ratio of light reflected from a surface to the light falling upon it; as affected by the lightness or darkness of the surface.

Reflection factor The ratio of the light reflected from a surface, to the light falling upon it. The surface, whether shiny or matt, will affect the nature of the reflected light.

Scalloping The effect gained from placing a row of light fittings too close to a wall. Where intended this effect can be pleasing, but more generally it becomes an unwanted intrusion on the space.

Sparkle A word which may be applied to rapid changes to light over time, most readily applied to the flicker of candlelight or firelight; sparkle may be applied to reflected or refracted light from small facets, such as those of a glass chandelier.


Ceiling/wall mounted The method by which light fittings are supported directly from the ceiling or wall.

Concealed lighting Concealed in the ceiling or wall configuration, to provide light on to adjacent surfaces.

Decorative lighting That which is designed to be seen and enjoyed for its own sake, such as a crystal chandelier. Alternatively it may be light directed on to objects to achieve a decorative purpose.

Downlight Light fittings giving their main light downards; these are generally recessed and include both wide beam and narrow angles.

Emergency lighting The lighting system designed to operate in the event of power failure to facilitate the evacuation of a building, or continuation of essential services. Various methods adopted to ensure a suitable source of power.

Floodlighting Generally refers to the exterior lighting of a building at night, by means of lights with controlled beams placed at a distance.

Functional lighting Lighting which is planned to provide light to satisfy the practical needs of a space.

General Diffusing light fittings giving all round light.

Indirect Lighting provided 'indirectly' reflected from ceiling or wall.

Local light/task light A light fitting designed to light a specific task, generally at individual control.

Louvres/baffles A means of shielding the light from a fitting or from daylight, to eliminate glare. They can be fixed or moveable.

Portable light fittings Such as table and floor standards designed to provide local light. 'Portable' uplights a useful addition.

Raising and lowering gear The apparatus applied to heavy 'light fittings' in tall spaces, to allow them to be lowered for lamp change and maintenance.

Spotlight Light fittings designed to throw light in beams of varying width and intensity.

Suspended The pendant method of 'hanging' a light fitting from the ceiling or roof.

Torchere Originally a decorative free standing 'candle holder'; a term sometimes applied to modern wall brackets.

Track mounted light fittings Both supported and energized, from the numerous track systems available; giving flexibility.

Uplight Light fittings directing their light up to the ceiling providing indirect light.

Wall washing The means of lighting by which a wall is designed to be lit evenly; several methods can be adopted to achieve this, some more successful than others.


BEMS Building Energy Management Systems. A means of computer control of lighting systems within a building.

Biomass A source of renewable energy which can be used in a building for activating building services, such as ''rape seed oil''.

Control gear Discharge sources require 'control gear' comprising amongst others: starters igniters transformers, capacitors, ballasts and chokes to operate. Incandescent lamps require no gear, giving low initial cost and making dimming simple.

Digital multiplex controller A sophisticated electronic controller used to monitor and vary circuits in a lighting system, such as might be used in a theatre.

Dimming Dimming controls are exactly what the name implies, a device by which the intensity of a light source can be reduced. All filament sources, both mains and low voltage can be controlled by simple dimmers.

Intelligent luminaires Light fittings with inbuilt sensors programmed to vary the light intensity, generally related to the amount of available daylight or occupancy.

Noise attenuation Noise reduction.

Passive building A building which by its configuration eliminates the need for mechanical ventilation, and reduces the need for daytime electric lighting

Photocell Measures illuminance at any position. When placed externally the photocell allows internal light control systems to react to changes in the weather, an element of 'daylight linking'.

Photovoltaics External panels on the southern exposure of a building designed to convert solar energy into useful electricity, a developing technology.

Scene set The use of more complicated electronic controls using a microprocessor, to permit different room appearances to be available at the touch of a button, with a number of scenes being 'present'; which can subsequently be changed automatically.

Stack effect The way in which hot air will rise in a chimney.

Thermal shutter An electrically operated mirror which tracks the sun, and redirects its rays to cope with low or high angle sun, at different seasons of the year.

Wind turbine A 'windmill' designed to generate electricity.


Atrium The courtyard entrance to a roman house, with an opening in the centre through which rainwater was collected. This opening also provided light to the courtyard and surrounding rooms. The word has now taken on the meaning of multistorey spaces which are daylit from overhead glazed roofs.

Barrel vault A continuous structural vault of semi-circular section, used from Roman architecture to the present; nowadays formed of reinforced concrete.

Brieze soleil Large vertical louvres externally designed to control the heat and glare from the sun. These are most used in hot climates.

Casemate A vaulted chamber built into a fortress for defence. Often used as a battery, or barracks.

Ceiling coffer A form of concrete roof construction, where, to add strength without increased weight, square holes or 'coffers' are omitted leaving a 'waffle' shape into which services can be placed.

Clerestorey (also clear-storey, and pronounced this way) The upper storey with windows above the side aisle roofs, giving high level daylight particularly in a church.

Conservation The protection of works of art against the deleterous effects of the environment. The control of light levels (particularly ultra violet) is a major component of conservation.

Dimensional cooardination The manner in which different building materials are planned to fit together.

Floor plate A modern term meaning the plan of a building at each of its levels.

Flying buttress An external abutment designed to take the horizontal thrust from an internal arch in a building. This was a device used in the mediaeval cathedral to permit lightweight construction of the external wall, akin to the curtain walls of today.

Folded plate Ceiling development of shell concrete construction.

Glass brick The development of 'bricks' made from glass in the 1930s allowed architects to design structural 'see-through' walls. The Maison Verre in Paris is a well-known modern example; although not widely used today they remain a useful architects tool.

Lighting gantry A light weight 'bridge' independent of the main structure of a building, providing support and electric power to light fittings.

Roof monitors/laylights The roof construction in which daylight is permitted to enter a space from overhead. In the case of factories they would be designed to control the entry of sunlight.

Roof truss A development of the beam supports to a roof allowing an openwork lattice to accept services.

Scale Scale is a matter of 'proportion,' the larger the scale, the less human the building will appear. It is sometimes difficult to judge the size of a particular building or interior until a person is added to give it 'scale'.

Shell concrete A thin skin of reinforced concrete, formed in a curve to span the roofs of large areas.

Spandrel The infill defining the floor level in modern building.

Sprinkler system Fire control by means of a system of water pipes which are designed to deluge water to douse a fire, when design temperatures are exceeded.

Sustainable building Applied to development which meets the needs of the present, and is at least as valuable to future generations, as the value of the environment exploitation that results. This can be applied to the concept of ''net zero energy demand''.

Undercroft A term in mediaeval architecture depicting the lower level vaulting of a cathedral, above which the main edifice is built.


Clear glass In terms of window glass this can be of several types and combinations, such as double or triple glazing, its principle characteristic being that it allows the view to the exterior to be unmodified.

Electrochromic glass Glass designed to respond indirectly to an electric current, which alters its transmission value.

Glass blocks Glass blocks have seen a recent revival, in allowing a wall which both lets in light and acts as a structural member.

Laminated glass Glass with internal sheets of plastic, laminated together to provide a sandwich for greater strength. The nature of the sandwich can be designed for different uses, such as U/V protection.

Low emissivity glass Glass where the radiating power of heat or light is reduced by having a heat reflecting coat applied to it.

Patterned glass Glasses rolled to give a wide variety of patterns which diffuse the light.

Photochromic glass Glass responding directly to an environment stimulus, such as heat or light, which alters its transmission value.

Prismatic panels Panels formed to alter the path of daylight, so as to redirect it either to cut out glare, or to introduce light for useful purposes.

Tinted glass Applied to glass which is modified by the addition of different materials to achieve a variety of colours such as green, grey, bronze or blue; the thicker the glass the more dense the colour. The glasses provide different light and solar radiant heat transmission characteristics.

Venetian blinds A time-honoured blind formed of controllable horizontal slats which can be used separately or combined in between sheets of glass to monitor daylight and glare.

Wired glass Glass with a wire mesh embedded, useful for security.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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