Think Efficient: Lighting
Lighting makes up about 10 per cent of the energy consumed in a typical home. You can reduce energy use for lighting by 50 per cent or more by making smart lighting choices and using more efficient lights. Spending a little time and effort to get the lighting right in your house can save you money on power bills and make rooms more comfortable and enjoyable. There is a vast array of light fittings and lighting systems available, but to be truly energy-efficient go for light emitting diode or LED lights.
Lighting for your home
The aim of lighting is to provide enough light to suit requirements, with some rooms in a home needing more lighting than others. Lighting for the home falls into four categories: general illumination, task lighting, ambient/mood lighting and outdoor lighting. If you know what kind of lighting you require for a particular situation you are halfway to having efficient lighting.
The degree of lighting intensity depends on personal preference and the kind of activity that goes on in a room. For example, kitchens are usually well lit for cooking, whereas in lounge rooms bright lighting may be a distraction from watching television and bedrooms are generally better with lower lighting levels. It is also important to consider the colour of walls and furnishings. Darker walls generally need more light to achieve the same level of perceived brightness as lighter walls.
General illumination can be of a fairly low level – enough to see by, but not so bright that the whole room becomes suitable for reading. Task lighting is for specific areas, such as desks or work benches.
Mood lighting may be important for some people: a home may have a feature that would benefit from a well-placed spotlight or up lighter, but lights like these are often left on for long periods and can consume a great deal of energy if the wrong lighting is used. Garden lighting is generally either floodlighting or feature lighting, where particular plants or garden furnishings are lit individually, often by coloured lamps, for effect.
Maximising natural lighting
The ultimate lighting is, of course, sunlight, and house orientation is crucial in this. In Australia, homes that face north receive the most sunlight, so if possible ensure the orientation of your home is right. When renovating, install north-facing windows to bring in light and warmth.
When orientation or renovation is not easy, you can install a skylight to transfer light from your roof to a room that needs brightening. A skylight usually consists of a transparent or translucent panel in the roof and a corresponding diffuser panel in the room directly below it.
Another option is to fit reflectors to already installed fittings. Fluorescent fittings can particularly benefit from a reflector. Putting in a reflector behind a single tri-phosphor tube can result in lighting levels equal to using two cheaper quality tubes with no reflectors. This means that combining a reflector and good quality tube can effectively halve lighting energy consumption.
Energy, power and voltage
It is important when considering the energy consumption of lighting to look at wattage, not voltage. Some bulbs, especially halogen downlights, are sold as ‘low voltage’, with many people thinking this equates to low energy consumption. This is not necessarily the case. The important factor is the power rating – 50 watts, for instance, is exactly that regardless of the voltage at which it is supplied and used. It is also advisable to look at the efficacy of the lamp. High-quality LED lighting will have an efficacy of greater than 80 lm/W (lumens per watt) – the bigger this number, the better.
Light emitting diodes (LEDs)
The most energy-efficient form of lighting, LEDs use a small piece of semiconductor material that emits light directly when an electric current is passed through. LEDs produce light in a range of colours without the need for coloured filters. In the past few years there has been an explosion in the variety of available LED bulbs and fittings.
Currently available LEDs have a lighting efficiency of between 12 per cent and 24 per cent, but that is increasing as manufacturers bring new models to market. In the future, LEDs may reach efficiency of up to 45 per cent. Unlike other types of lighting, LEDs don’t contain mercury, reach full brightness immediately and have a much greater lifetime of at least 30,000 hours.
While LEDs are expensive, their cost is coming down. Many bulbs are over $30, but if you are happy to buy directly from overseas suppliers, it is possible to purchase them at about $1 per watt.
Fittings, bases and adaptors
Installing LED bulbs into standard fittings may not be straightforward because most LEDs are made for the US and European markets and not for Australian bayonet-style bulb bases. Fortunately, there are bulb base adaptors that solve this problem: simply screw the adaptor into the fitting and the bulb into the adaptor.
When building or renovating it is best to consider dedicated LED fittings – these are complete fittings designed as LED lights from the ground up. Dedicated fittings come in a large array of shapes and sizes, from flat panels to flush-fitting downlights, wall washers, up lighters, oyster fittings and even outdoor floodlights. In each there is one or more LEDs mounted on a metallic circuit board attached to a heatsink or the fitting itself to dissipate heat.
Heatsinking and ventilation
Many early LED lamps and fittings had inadequate ways to dissipate the heat they generated, so the LEDs ran at excessively high temperatures, reducing light output and shortening lifespan. Most LED bulbs now have adequate ways to cool themselves, although there are some that still push the limits with too much wattage and too little heatsink surface area to dissipate the generated heat. This problem is most common in downlight replacement lamps.
When selecting an LED lamp, be mindful of the fitting into which it is to go – there is no point in a lot of heatsinking if the bulb is used in a fitting that simply doesn’t allow the heat to dissipate. Heatsink material and finish also play a role. Some manufacturers are still making bulbs with chrome-plated heatsinks which do not emit heat well. A chromed heatsink may cause a lamp to run 20 degrees hotter than the same heatsink in a black anodised or high-emissivity finish.
Colour temperature, lux and lumens
LED lighting often comes with a ‘colour temperature’ measurement. Colour temperature in Kelvin (K) relates to the colour of light emitted by a lamp. Warm white is generally any number up to 4000K. Neutral white is 4000K to 5500K and cool white or daylight white is 5500K and above. When the number is lower, the light is warmer and redder; the higher the number, the cooler and bluer the light. Most people prefer the yellowish glow of ‘warm white’ light yet this is simply an accustomisation issue and living with a neutral or cool white light for a week or two will generally overcome this predisposition.
Light output is measured in lumens. The lumen figure allows you to compare different LED bulbs of the same power: for instance, one 8-watt LED can generate light of 500 lumens, while another gives off 600 lumens. For greatest energy efficiency, choose lamps of at least 80 lumens per watt.
A closely related figure to the lumen is the lux. Lux is lumens per square metre, so a 500-lumen light source that is directing all of its light onto a
4sq m surface will produce 125 lux at that surface. Lux allows you to compare the effective brightness of each light source at a given distance and make a decision on what best suits your needs.
John Knox is a lighting specialist and webshop manager at the Alternative Technology Association (ATA). The ATA is a not-profit-organisation promoting sustainable living. Speak to John at the ATA’s advice service on efficient lighting.