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Bath Preservation Trust and the Centre for Sustainable Energy Artificial light The efforts of the Georgians and Victorians to bring daylight into their homes were in part a response to the poverty of the artificial light available to them. Oil lamps, candles and open fires were the only choices for the residents of Bath until the introduction of gas light in the nineteenth century and eventually electric light after World War I. Since then we have become used to living in brightly lit interiors and have, arguably, become lazy in our use of artificial light because of its very abundance. Reducing the energy we use to light our homes is therefore a matter not only of the technology we use but also the care we take in designing and using interior lighting. Lighting design The interior of a traditional home in Bath will not necessarily look at its best if it is comprehensively and consistently lit. Shadows can be as important as the lighting itself in defining the quality of an illuminated interior. There are only a few places within the home that must be brightly lit, such as desks and kitchen surfaces. Lighting designers typically divide interior lights into three categories: task, feature and ambient lighting. Task lighting is trained on areas where specific activities are undertaken, such as food preparation or reading. Feature lighting is used either as a feature in itself or to illuminate features in a room which give it special character, such as pictures or architectural details. Ambient lighting provides the necessary background lighting to enable people to move around the room freely. Every room does not need all three types of lighting. These categories are simply a guide to help you think about your use of lighting and to consider whether you could get a better result for less light. The most important time to think about this is during a major renovation. If you don’t specify this carefully, you risk ending up with the standard approach in modern renovations: banks of ceiling recessed downlighters smothering the room with flat, energy-guzzling light. Low energy lighting The tungsten filament electric bulb has changed little since its invention by Thomas Edison over 100 years ago. It is notoriously inefficient because most of the electricity A central ceiling lamp provides limited ambient light. However the goal of comprehensive illumination should perhaps be resisted: ‘Our ancestors, forced to live in dark rooms, presently came to discover beauty in shadows, ultimately to guide shadows towards beauty’s ends.’ (Junichiro Tanizaki, In Praise of Shadows) 34
Improving the energy efficiency of traditional homes in the City of Bath Compact fluorescent bulbs come in all shapes and sizes including ceiling-recessed downlighters used to power it turns into heat not light. These bulbs are being phased out within the European Union but they remain popular because of the warmth of their light. In contrast, fluorescent tubes have a reputation for producing a cold blue light which is not attractive in domestic interiors. Happily, the lighting industry has responded to these problems and it is now possible to buy low energy bulbs that produce a warm light. Although low energy bulbs are often more expensive than old-fashioned tungsten bulbs, they last a great deal longer and use less power so are cheaper over their lifetime. There are three types of low energy lighting suitable for homes: fluorescent tubes, compact fluorescent bulbs and light-emitting diodes (LEDs). All three consume far less energy than traditional incandescent bulbs. For example, a 60W incandescent bulb can be replaced by a 11W compact fluorescent bulb and a 40W halogen downlighter can be replaced by a 3W LED. Fluorescent tubes are usually only used in kitchens and bathrooms or for feature lighting where the source can be concealed. Early compact fluorescents gained a reputation for ugliness due to their egg-whisk appearance but today the tube is usually disguised by an opaque bulb-shaped sheath. Consequently compact fluorescent bulbs look little different from traditional incandescent bulbs. Furthermore it is possible to buy miniature compact fluorescent bulbs including replacements for candle bulbs and ceiling downlighters. Different brands and types of compact fluorescent bulbs have different qualities. In particular, some have a warmer light than others and some take time to reach full brightness. So be prepared for a switch from incandescent bulbs to compact fluorescent bulbs to involve some change in the quality of the light. A little experimentation with different brands may be worthwhile before a complete refit. You cannot control an ordinary compact fluorescent bulb with a dimmer switch as they are not designed to dim and so will simply turn off. However special compact fluorescent bulbs are available which can be used in these circuits. The reputation of LEDs has also suffered from the poor quality of early lamps which tended to produce a blue light. These problems have now been overcome and you can now buy ‘warm white’ LED bulbs and down-lighters. Their light is not quite as warm as the compact fluorescent ‘warm white’ bulbs but they come on instantly and can be dimmed in the same way as traditional incandescent bulbs. If you want to compare the ‘warmth’ of the light of different bulbs before buying them, compare the ‘colour temperature’ specified on the packaging. A lower colour temperature means a warmer light. LED lamps are made from collections of small diodes grouped together. However, like modern compact fluorescent bulbs, these are designed to look like traditional bulbs and fittings. If you are replacing your existing bulbs with low energy bulbs, pay attention to the voltage required, especially for ceiling recessed downlighters. Some halogen downlighters run on mains voltage (240V) and can be replaced directly by miniature compact fluorescent GU10 bulbs. Others run off hidden transformers at 12V, for which LED replacements are available if you don’t want to take out the transformers. Planning and building control Listed buildings Listed building consent is not usually needed to change light fittings as these are not considered to be fixtures of a building. However you may need consent if you want to bury new wiring in original plasterwork, if you have historic fittings such as chandeliers or if the existing fittings form part of the designed decoration of the interior. Building regulations Changing light fittings or bulbs does not require Building Regulation approval. If you want to install a new circuit or fixed cabling, the work should be carried out by a person registered on a Part-P registration scheme which allows them to self-certify the work. The organisations running these registration schemes are Ascertiva Group Ltd (NICEIC), Benchmark Certification Ltd, BSI, Building Engineering Services Competence Accreditation Ltd, ECA Certification Ltd and NAPIT Registration Ltd. 35
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