Residential Lighting Design E-Book

Marcus Steffen

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 285

Veröffentlichungsjahr: 2014

Beschreibung

Good lighting is essential to a building. An effective design is not just about introducing light into a space, but rather an appreciation of how the space will be used. A good lighting design is so intertwined with the building that it is only noticed in its absence. This book introduces the tools of the lighting designer and explains how to produce a lighting design for a home. Looking at the nature of light and introducing different lamps and light fittings available, it explains the basics of lighting design and how to provide atmosphere through the play of light and shadow. It gives room-by-room analysis of good lighting design and gives advice on controls, plus an overview of the pitfalls of dimming and energy saving. Illustrated throughout with 132 stunning images and creative ideas.

Leseprobe

Residential

LIGHTING DESIGN

MARCUS STEFFEN

THE CROWOOD PRESS

First published in 2014 byThe Crowood Press LtdRamsbury, MarlboroughWiltshire SN8 2HR

www.crowood.com

This e-book first published in 2014

© Marcus Steffen 2014

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.

British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.

ISBN 9781847977571

DisclaimerThis book is intended for guidance on wiring and installation only. Regulations do change over time, and all lighting should be installed by qualified professionals to the latest set of standards. Wiring diagrams are presented to give knowledge of the principle of installation, and all installations should refer to the manufacturer’s specified installation diagrams. The author and publishers accept no responsibility for incorrect installation or wiring.

DedicationThis book is for my wife and children, whose love and support bring me inspiration every day.

AcknowledgementsI would like to thank John and Leigh Everett of Mr Resistor. Without them starting me on the path to being a lighting designer I would never have had this chance to write a book. They shared their vast knowledge and gave me freedom to create and make mistakes, learning in the process. I have been allowed to learn and progress with their support and help. Thank you for my wonderful clients, who let me into their lives and homes, and allowed me such a personal view into how they live. Without willing clients who also have a passion for lighting I would not be able to create good lighting designs. Thank you to Alan Hughes and Atousa who gave me the opportunity to lecture at the Inchbald School of Design. They have been helpful and supportive and given me the wonderful task of introducing interior designers into the world of lighting. Finally, thank you to my wife, Emanuela, for her patience and understanding in the time I needed to write this book. She has supported me and helped take care of our family while I have sat trying to convey my thoughts onto paper.

CONTENTS

  1    The Nature of Light

  2    Lamps

  3    Light Fittings

  4    Basics of Lighting Design

  5    The Heart of the Home: the Kitchen

  6    Luxury and Style: the Bathroom

  7    Comfort and Relaxation: the Living Room

  8    Entertaining with Drama: the Dining Room

  9    The Retreat from the World: the Bedroom

10    Lighting Controls

11    Creating a Lighting Plan

Index

CHAPTER 1

THE NATURE OF LIGHT

LED strip set into a recess under the handrail illuminates the stairs, while pendants and wall lights provide general and effect lighting within the space.

Light is a complex medium with which to work. While light itself is understood by science, how it is perceived by humans is still not fully comprehended. Different people react to light in different ways, and it is important to be sensitive to what people like and dislike with certain properties of light.

LED lighting in a living room with an LED strip used as a guide light inthe hallway. (Photo: Mr Resistor)

Light, and this book deals only with visual light, is the emission of energy within a certain bandwidth range, known as the visual spectrum. The range of wavelengths is generally between 390nm and 700nm, though this can vary depending on the person. Light can be received directly from a light emitter, such as a lamp, but it can also be seen as a reflection from other objects. The colour of objects is determined by the light that is reflected from their surfaces, and thus received by the eye.

Light travels in straight lines, and so it is easy to predict where light will fall within a room. Standard mathematics can be used to determine if a light source will be visible and have a high glare, or if light will fall on a particular surface. When light travels through different materials, such as air and glass, then the direction of the light will change. Most of the time this is not relevant, but when lighting glass it is important to remember the principle of total internal reflection. If the light contacts the glass at a very shallow angle, almost parallel with the surface of the glass, then it will not penetrate it, but reflect off it and away, similar to a mirror. This is important to note, since in some cases it will not be possible to light through a piece of glass, such as a step, if the light is being transmitted next to it.

Daylight being broken as it passes through crystal door handles. (Photo: Marcus Steffen)

PROPERTIES OF LIGHT AND ELECTRICITY

Luminous Intensity

Luminous intensity is the measure of visible light in a particular direction per solid angle. The SI unit for luminous intensity is the candela (cd). This gives a good indication of the intensity of the light emitted from a lamp. Most lamps with a beam angle (generally up to 60°) will have a peak intensity, or candela, value. This allows comparison between different lamps with a beam angle and gives an idea of the maximum light output.

Luminous Flux

Luminous flux is the measure of the visible light output of a light source (a lamp). The SI unit for luminous flux is the lumen (lm). Whereas luminous intensity deals with visible light emitted in a particular angle, luminous flux is the light emitted all around a light source. The lumen value is generally given for unidirectional lamps, such as fluorescent tubes and standard incandescent lamps. This is another way of comparing the light output between different lamps to see which is brighter.

Illuminance

Illuminance is the measure of luminous flux per unit area. The SI unit for illuminance is lux (lx). One lux is equal to one lumen per square metre. In most homes an illuminance level of between 100lx and 500lx is required, depending on the different areas in the home. A house would not be lit with 500lx through its entirety, as this may only need to be achieved on some work surfaces. Most residential lighting designs do not need or want measured illuminance levels, but it may be helpful to compare different lamps and the actual light output. Most lamp manufacturers produce a light cone, which shows the peak illuminance at different distances. These provide a quick comparison of the actual light output from a lamp, and show which is brighter.

Power

Power in lighting refers to the electrical power used by the lamps in the system. The SI unit of power is the watt (W). Almost all equipment will have a maximum wattage that it can control. Some will have a minimum wattage as well. It is important that these limits are observed, since if they are exceeded then it could mean early failure of either the light fittings or the equipment. For example, many dimmer switches have a maximum wattage of 250W. If the lighting circuit carries more than 250W, for example three 100W incandescent lamps, then this could cause the dimmer to overheat. It is normally acceptable to have less than the maximum wattage on lighting equipment, unless it is a fluorescent or metal halide lamp, in which case it must be matched.

Efficacy

Efficacy is similar to efficiency, but is the ratio between two figures with different units. In lighting terms, efficacy relates to the lumen to watt ratio. This is a common way of measuring how low energy a light source is. It is the number of lumens emitted divided by the number of watts of power consumed, and is noted with the unit lm/W. There are different variations of the lm/W ratio. Some take into account the power losses of transformers and ballasts used by a light fitting (commonly noted as a circuit watt), and some also take into account the light lost when a lamp is fitted into a light fitting (the luminaire lumen value as opposed to the lamp lumen value).

Electric Potential

Electric potential is measured in Volts (V). An electrical circuit will have a voltage associated with it. In most cases this matches the national voltage, provided by electric companies to homes. In the United Kingdom this is 230V AC, whereas the United States uses 120V AC. There are variations across the world, so if light fittings are being purchased from other countries, it is important to ensure that they will work in the installation.

Current

LEDs generally require a constant current to make them emit the maximum possible light. Rather than a specified voltage, like most other lamps have, many LEDs have a specified current, such as 350mA or 700mA. It is important to obtain an LED driver that matches this to enable them to work at maximum efficiency, and avoid damaging the LEDs.

Correlated Colour Temperature

The correlated colour temperature (CCT) of a lamp is the measure of the warmth of the light emitted from it. It is measured in Kelvin (K). Incandescent lamps have a colour temperature of 2700K, whereas fluorescents can have colour temperatures ranging from 2200K (orange/white) to 8000K (blue/white).

Ensuring that the correct colour temperature is used is essential to any lighting design. If cool colours are used in rooms for relaxation then they will look harsh and uninviting. If warm colours are used exclusively then the rooms may appear dirty and old. Finding a balance between different colour temperatures can be quite difficult and it is worth experimenting with different lamps of different colours to find the right combination.

The range of colour temperatures of white. (Photo: Marcus Steffen)

COLOUR TEMPERATURES

2200K

–

Orange/White

2700K

–

Interna (incandescent and mains voltage halogens)

3000K

–

Warm White (low-voltage halogen)

3500K

–

Neutral White

4000K

–

Cool White (commonly used in offices and shops)

6500K

–

Daylight (used in offices, very cold with blue tones, closest to daylight)

8000K

–

Blue/White (very cold white, with a lot of blue in the colour)

As a general rule, if a high level of light is required, it should be cooler. Utility rooms, for example, work very well with a very bright light at the 3500K–4000K CCT range. If a lower level of light is required, say for a bedroom, then warmer colour temperatures should be used, between 2700K and 3200K. It is acceptable to have different colour temperatures within one room, and they can work well together, but if two light sources are serving the same purpose, such as illuminating a work surface, then their colour temperature should be matched. However, if the surfaces being lit are different colours, then it may be acceptable or desirable to have two different colour temperatures lighting them. Just as with paint and fabrics within a room, the colour temperature is something that needs to be tailored to the room and matched to the décor.

It is important to note that lamps with a filament change colour as they are dimmed. As the filament cools, it will go from emitting a cooler white light to emitting colours more in the yellow and amber ranges. Incandescents and halogens all become warmer as they dim. In contrast, LEDs maintain the same colour temperature no matter what the brightness. This is important to bear in mind when choosing the lighting within a room, since an LED may not be able to provide both a clean, bright light in the cooler ranges and a warmer tone when dimmed. It may be necessary to use other light sources to achieve this warmth, such as table lamps with shades and incandescent lamps. Fluorescents are even more unpredictable, with some fluorescent lamps emitting a cooler colour temperature when dimmed.

Colour Rendering Index

The colour rendering index (CRI) is a measure of how well a light source matches a particular spectrum standard called a black body radiator. An incandescent lamp will match the black body radiator, and has a CRI of 100. It is used as a guide to how well light shows colours on a surface. A good example of a very low CRI lamp are the sodium lamps used in some street lighting, giving an orange/yellow light. It is almost impossible to discern different colours below one of these lamps, since they all look the same, and these have a negative value CRI. The CRI of a lamp is a good measure of how well the lamp will show colours. If the CRI rating is in the 90s, then this is exceptionally good; if it is in the 80s it will be good, but not amazing. Anything below 80 is not really suitable for residential use.

CHAPTER 2

LAMPS

A small LED spotlight illuminates a crystal decanter, with beautiful patterns created from the refraction of the light through the crystal.

There are numerous different types of lamp on the market, each with its own benefits and problems. From the humble incandescent lamp to the LED, the range is wide and bewildering. Most people refer to them as bulbs, but within the lighting industry the correct term is lamp. This can lead to some confusion between lighting specialists and their clients. Choosing the correct lamp forms an essential part of creating a good lighting design for the home. If the wrong colour or beam width is used, it can ruin the atmosphere of a room, and can even make a space unusable. The correct lamp will enable everything to work as intended, and enable a house to become a home.

This section discusses the different types of lamp, and lists the different characteristics that need to be taken into account. This will act as a guide to what information to look for when choosing lighting for the home, and ensuring that the product is supplied as intended.

A decorative incandescent lamp with an extended filament. (Photo: Mr Resistor)

INCANDESCENT

The incandescent lamp has been available for over a hundred years. Designed with a tungsten filament heated up to burn brightly, it has formed the basis of electrical lighting since it became available. Its warm glow has brought about revolutions in lifestyle and it has become a design icon in its own right. It is both loved and hated for a number of reasons, and has latterly come to be regarded as a symbol of inefficiency as global warming has become a central issue in the world.

A selection of different incandescent lamps with different lamp holders. (Photo: Mr Resistor)

Incandescent lamps produce light by heating a wire to a high temperature, causing it to glow white hot. The repeated heating of the filament means that the lamp normally has a short life, of between 500 and 1500 hours. Longer-life versions have been made, but generally manufacturing methods and cost have meant that they became niche products. In addition, incandescent lamps do not have a good efficacy rating. A lot of the energy provided by the electricity goes into heat generation, while only a small portion is given out as light in the visible spectrum. These lamps give out a broad, mostly even spread of light in the visible spectrum, with slightly more red and yellow light emitted, giving them their distinctive warm colour (2700K). Due to its wide spectrum of light emission, the incandescent lamp is also closest to the ideal light source for the Colour Rendering Index, giving it a CRI rating of 100. While CRI is not a perfect way of measuring how colour appears on objects, it does give a guideline. Comparisons between colour temperature and CRI can help determine how close other sources of light are to incandescent light.

The incandescent lamp has been the main source of light for almost all homes over the last century, and has become integrated into the psyche of humans. The warm light it gives has carried on the image of fire in creating a warm atmosphere to return to after a hard day’s work. Creating a safe, inviting haven away from the world is the aim of the home, and this warm light forms part of that image. While rising energy costs mean this lamp is becoming much more scarce, it is essential to know the type of light that is generated from it since it has formed the basis of residential lighting for the last hundred years.

Common incandescent lamps and lamp holders. (Diagram: Marcus Steffen)

TUNGSTEN HALOGEN

Tungsten halogen lamps are normally used in directional reflector types, commonly known as low-voltage halogen or halogen spotlights. Using an extra halogen component inside the lamp’s make-up enables it to burn at much higher temperatures, producing more light, and it lasts longer than normal incandescent lamps. The majority of these lamps come with a reflector, focusing all the emitted light into a beam. This enables light to be concentrated on a point rather than diffused in all directions. They are normally available in a large range of different beam angles, from as narrow as 8° to as wide as 60°. Due to the higher temperature at which the filament burns, most halogen lamps will not work on normal household voltage. They require a transformer to reduce the voltage down to between 12V and 24V, depending on the lamp type. This increases the current through the lamp, and this enables the filament to reach maximum temperature.

A close-up of a halogen dichroic lamp, showing the centre capsule lamp and the reflector. (Photo: Mr Resistor)

The colour of halogens is similar to that of incandescent lamps. Low-voltage halogens are normally slightly cooler, producing light with a colour temperature of around 3000K. As with incandescent lamps, the light colour changes if they are dimmed, with the colour temperature varying from 3000K down to 2000K–1500K at the lowest levels.

Halogen lamps with reflectors form a major part of a lighting designer’s toolbox. The control that this gives over light and where it is applied to the surfaces of a room can enable the tailoring of light to a particular situation and gives a large amount of flexibility in how light is used. They enable good task lighting onto work surfaces, or can be used to highlight artwork or sculpture. They can also be used to provide general light throughout a space.

Diagram showing how a dichroic reflector focuses and controls the light into a beam. (Diagram: Marcus Steffen)

Most halogen lamps come with a 50mm dichroic reflector with the MR16 shape. There are also smaller versions (35mm and 25mm diameter), with MR11 and MR8 bodies respectively. All of these use a dichroic reflector, made of glass. This is used to reflect the light forward into a beam, while allowing the heat to escape out of the rear of the lamp. This prevents the heat being projected forward, causing heat gain in a room and making it uncomfortable to remain underneath the spotlights for a long period of time. There are specialist versions of this type of lamp, known as Reflekto or heat forward lamps, which have coatings that project the heat out of the front of the lamp. These are normally used in specialist fittings that either are enclosed at the rear, or have delicate electrics behind the lamp mounting position. Care should be taken when replacing these lamps to ensure the correct type – heat forward or backward – is supplied, since damage could be done to the light fittings if the incorrect type is installed.

Less common types of halogen lamp are the AR111 and AR70 ranges. These are commonly known as anti-glare bar lamps. Sometimes the notation of QR111 or QR70 is used, but they refer to the same lamp. Instead of a glass reflector these use a metal reflector. In addition to this, the halogen capsule lamp that provides the light is covered by a cap (held by a bar, hence the name ‘anti-glare bar lamp’). This means that the halogen capsule is not visible, and this reduces the glare from the lamp. The light is reflected from the metal reflector out into the room. This has the effect of giving a soft light. The nature of the metal reflector means that it allows tight control over the beam angle, with narrow beam lamps achieving a 4° beam angle. These lamps are typically found in museums and art galleries due to the precise control they can achieve, allowing the light to be directed onto specific items or artworks. They are also fantastic for both general light and spotlighting of artwork in the home, especially where there are high ceilings, since they are available in higher brightness versions than the normal dichroic lamps.

Newer halogen lamps sometimes come in a special version, known as IRC (Infra-Red Coating). These lamps are more efficient due to a special coating over the internal surface of the halogen capsule lamp, which reflects the infra-red light range back into the capsule lamp, allowing it to burn at higher temperatures and producing more light. With the modern requirements for higher efficiency lamps, these are becoming the standard lamp.

The Art Cabin in Southfields, London, using AR111 lamps to focus light onto artwork. (Photo: Mr Resistor)

The majority of halogens used are the reflector types discussed above, but there is another range of halogen capsule lamps that are used either in very small fittings, such as those positioned under kitchen cupboards, or in specialist track-mounted lights for illuminating artwork. The fittings for these lamps are normally supplied with custom-made reflectors to aim the light in a particular direction, and give very good beam control. The most common base types are the G4, the GY6.3 and the G9. The G4 and the GY6.3 are both low-voltage versions, requiring a transformer to operate. The G9 is a mains voltage lamp, meaning no transformer is required to use it. This type of lamp is also becoming popular for use in wall lights, after the banning of standard non-directional incandescent lamps.

Common halogen lamps and lamp holders. (Diagram: Marcus Steffen)

LIGHT EMITTING DIODES

Light Emitting Diodes (LEDs) have been around for over fifty years. They were originally used as indicator lights on almost all electrical equipment, but since the discovery of the blue LED, followed by a coating technique to obtain white light, they have been seen as the future of lighting. Extremely efficient, and with a wide range of colours, this is the fastest-growing area of lamp development in the lighting industry. The potential for both reduced energy consumption and reduced waste means that LEDs will be the future of lighting in the world. There is a wide variety of LEDs available on the market, and care must be taken when selecting which one to use in a project. The fact that they are being constantly developed, and more efficient versions released, means that there is no set ‘standard’ on the market, and so each one must be analysed to see if it gives the desired light.

LEDs are fixed to a circuit-board of some description, and normally other electrical components are required. In general, a single LED will have a beam angle of between 110° and 140°. Almost all LEDs are sold in a body of some description, be it on a long strip with multiple LEDs, or in a lamp form with reflectors to focus the light. They almost always require a transformer of some type, depending on the kind of LED being used. When referring to LEDs, the transformer is normally known as an LED driver so as to avoid confusion with low-voltage halogen transformers. Sometimes LED lamps will work on mains voltage, but this normally means that the driver is built into the body of the lamp.

LEDs come in a wide variety of colours, including many whites. The first White LEDs were a very cold, white light, with a colour temperature of around 6500K–8000K. This is almost a blue/white colour, due to their development from Blue LEDs. With the development of the technology, there are now LEDs available in whites from very warm (2700K) to very cold (6500K) and many in between. Unfortunately the manufacturing process of LEDs means that accurate colour matching between batches is very difficult to achieve. There are always variations between batches, and even within batches. Manufacturers use a binning method, selling LEDs in colour bins of colour temperatures. Purchase of LEDs can be made from a very narrow bin range, resulting in high cost, but good colour temperature matching, or from a wide range of bins, meaning that there will be a reduced cost, but wider-ranging colour temperatures on the LEDs purchased.

LEDs are also available in colours, the most common of which are red, green, blue and yellow/amber. Sometimes single-colour LEDs are used to provide an accent light or they are used as marker lights. Red, green and blue LEDs are also combined into light fittings which allow the mixing of these three colours. These are known as colour-changing or RGB lights. Since almost any colour can be produced by mixing red, green and blue, they can be used to create colourchanging fittings to add fun or dramatic lighting to an installation. However, while the RGB lights can produce a huge range of colours, they are not particularly good at producing whites. White requires a very broad spectrum of light, and the narrow-spectrum bands of the red, green and blue make it difficult to produce a wide enough spectrum. Some RGB lights incorporate a cool white or warm white LED so that white light can also be obtained from the same fitting. Care should be taken when using coloured LEDs to ensure that they do not clash with the interior design in which they are placed, though they can be a great asset when used correctly.

An LED flexible strip light. (Photo: Marcus Steffen)

LED lamps have the potential to be dimmed. LEDs themselves rely on a certain amount of current from the LED driver to work at maximum brightness, and reducing this current reduces the amount of light emitted. The key to dimming LEDs is to have an LED driver that can be dimmed. As well as the standard phase dimmers found in most houses, there are more specialist dimmers available that might be required, depending on the LED driver being used. The common dimmer types used for LEDs are 0–10V, DSI, DALI and DMX. It is important to note that all these alternative dimming types require extra wiring to be installed in a property, different from standard cables installed by electricians. It is essential to make sure that the type of dimming is known before the wiring is done in a property so that the correct cables are installed for the LED types being used.

Unlike incandescent and halogen lamps, LEDs do not become warmer when they are dimmed. They remain at their set colour temperature, simply reducing the light output. The majority of people are used to this change in colour, achieving that warmer, ‘cosier’ atmosphere in a room, so using LEDs will give a different light that some may not like. Some LED light fittings incorporate a variety of white LEDs, and vary the brightness of each of them as they dim, simulating the effect of incandescent lamps.

LEDs generally have a very long lifetime, between 20,000 and 50,000 hours. The key to a long lifetime is correct cooling for the LEDs. While LEDs do not give off heat like an incandescent or halogen lamp, they do produce high heat on the circuit board on which they are mounted. High temperatures reduce the life of the LED, so correct heat removal is very important. The long life of LEDs means that there can be large cost savings in using them, in terms of both energy consumption, and in reduced maintenance and replacement costs.

There are two types of LED lamp available on the market. The first are high-output individual LEDs, which are normally used as spotlights or floodlights. These run at a very high constant current, and output a large amount of light for one LED. They are used in retro-fit LED lamps for downlights, as well as dedicated downlights with the LEDs built into the body of the fitting. They require heat sinks to remove the heat generated by the electrical current on the PCB. These can vary wildly in size, and all depend on the design and circuit construction of the LED itself. A good heat sink is very important, since it cools the LED itself, which will extend the life of the lamp. A poorly cooled LED will have a much shorter life, which could drastically reduce any predicted savings over the long-term life of a project.

The second type of LED is a small, standard output one, used in large groups to produce light. These are commonly used for creating long strips of LEDs. While each LED is less powerful than a high-output LED, many more can be fitted onto a circuit board, which can even be made to be flexible. LED strips are used for linear lighting solutions, such as under cupboards and plinths, and in furniture. They have a wide spread of light which enables them to wash surfaces with light.

T5 fluorescent lamps. (Photo: Mr Resistor)

FLUORESCENT

Fluorescent lamps are commonly found in commercial properties, but their use in residential lighting has increased greatly due to high energy costs. Their technology has improved a vast amount since the days of flickering tubes casting a cold, uninviting light around a room. Now fluorescents are available in a range of colours, and with the development of modern ballasts (the fluorescent equivalent of a transformer) the flicker is all but eliminated.

Fluorescent lamps work by passing an electrical current through a gas, reversing the direction of travel of the current thousands of times a second. Light is generated through the reaction of the gas, and a coating on the glass tube. The light emitted from tubes is given out in all directions evenly, creating a general distribution of light that is difficult to achieve with incandescent or LED. Fluorescent lamps also have a high light output for a low power input, giving it a high efficacy.

Fluorescents are available in a wide range of colour temperatures, from 2200K (extremely warm, almost orange) to 6500K (ice-cold blue/white, associated with daylight). This gives a wide choice of colours to match interior decoration and style. Most of the time warmer colours are used (2700– 3000K), but sometimes 4000–5000K colours can be good in very dark, cold-coloured interiors.

Fluorescents can be dimmed, but require a special ballast and extra wiring. The most common way of dimming in residential properties is 0–10V, though sometimes other methods are used. No matter which method is used, it is important that this aspect be considered early on in a project, since it cannot be changed at a later time without resulting in significant work. It should be noted that the colour can vary slightly with fluorescents when dimming. They sometimes become slightly cooler or warmer, depending on the colour type and the composition of the tube. Fluorescents cannot normally be dimmed lower than 10 per cent, since the tube will begin to flicker. If very low levels of light are needed then it would be best to consider an LED light source instead.

There are number of different fluorescent lamps available. The most common type is a retro-fit lamp for screw or bayonet lampholder. These give a good light, but are generally not dimmable. The fluorescent ballast is placed in the body of the lamp, hence they are larger than incandescent lamps. They come in a range of different colour temperatures, but 2700K is by far the most common. Standard edison screw (E27) and bayonet (B22) versions are available, but smaller versions are also made: generally the small edison screw (E14) and small bayonet (B15). It is important to check the size of the whole lamp when looking at the smaller lamp holders, since a lot of light fittings that use the smaller versions also have little space around them, and the larger body of a retro-fit compact fluorescent lamp will not fit inside.

Chart showing the different lengths, wattages and lamp holders of standard linear fluorescents. (Diagram: Marcus Steffen)

The retro-fit lamp is a type of compact fluorescent. These are straight fluorescent tubes that are shaped into a more compact size, usually with a number of U bends. As well as the retro-fit types, compact fluorescents also come with dedicated lamp holders. These are used much more in commercial premises, though they have become quite popular as an energy-efficient light in homes, especially when used as wall-mounted uplights. The ballast is located outside the lamp, which allows for a much higher light output and efficiency. It also means that only the matching compact fluorescent lamp can be used. It is not possible to down-rate the lamps, since the ballast is designed to run a particular length and wattage of fluorescent. It is possible to dim a compact fluorescent with a remote ballast, but a resistive or inductive dimmer cannot be used. Generally they are dimmable using SwitchDIM, 0–10V, DSI or DALI. They all require extra cabling and a particular type of dimming control, so it is important that the wiring is allowed for this at the first fix stage of a project to ensure that it is possible. If the wiring has already been done, then a large amount of work will be needed to correct it, since the walls and ceilings will have to be opened up again.