Energy

For each type of lamp, energy use (and running cost) increases as the wattage increases. A 15W compact fluorescent lamp will produce the same light output as a 75W incandescent bulb.

The New Zealand Herald reported on February 21 2007 that: “If all 60,000 households in Waitakere City replaced five standard 100W bulbs with five 20W compact fluorescent lights, the electricity saved would be equivalent to the annual electricity usage of 3504 households”.

Light emitting diodes

Light emitting diodes (LEDs) are very energy efficient, and are one of the most rapidly developing areas of lighting design. They are extremely long lasting (between 50,000 and 100,000 hours). Up to now they have been expensive and had limited availablility for domestic use, but this is changing.

Fluorescent lamps

Fluorescent lamps provide light by causing a phosphor coating (triphosphor) on the inside of the glass to glow. They are very energy efficient lights (using as little as 20% of the energy to provide the same light output as an incandescent lamp) and last for much longer (up to 10,000 hours). They can provide light in a range of colours.

They cost more than incandescent bulbs to buy, but their longer life and lower energy use give lower long-term costs.

Fluorescent lamps are not suitable for rooms where they will be used for very short periods (which may include toilets or bathrooms). This is because they need a ballast to start them (which uses more energy than the light itself for a few seconds), take a minute or so to reach full brightness, and have extra wear when they are starting up. They may also be unsuitable for exterior use as they produce less light in low temperatures.

Light output from fluorescent lamps drops slightly as they age. You may need to consider this when specifying the appropriate wattage.

Fluorescent lights contain mercury and cadmium and should be disposed of as hazardous waste.

Types of fluorescent lamp

Compact fluorescent lamps:

• are also known as long-life bulbs
• can fit into conventional bayonet or screw-fitting light sockets
• come in styles like stick, globe, circular and square
• can replace incandescent light bulbs in most light fittings – an increasing range of products will become available as technology develops
• have an integral ballast.

Fluorescent tubes:

• are available in straight or circular styles
• require special fittings
• are good for background lighting but not for directional lighting
• are most suitable for kitchens, garages and workshops and non-adjustable task lighting
• have a separate replaceable ballast.

Newer NG triphosphor tubes have better energy efficiency than the older monophosphor tubes and use 20% of the mercury. Two of the newer tubes can replace three of the older tubes and give the same light output.

Also available are miniature fluorescents (around 24 mm wide by 38 mm high) that are:

• dimmable (down to 7.5% of maximum output) and
• colour temperature controllable.

Fluorescent lamp ballasts

Ballasts are typically built in to a compact fluorescent lamp, but are separate for a fluorescent tube. The ballasts generally last longer and are more expensive than the lamp, which can be reason to use a detachable lamp.

Specify electronic ballasts. Although more expensive, they are more energy efficient, longer lasting, start the lamp quicker, produce less flicker and are dimmable. Older magnetic ballasts cannot be used with standard light dimmers.

Halogen lamps

Halogen lamps are a type of incandescent lamp made of quartz that uses halogen gas to extend the life of the tungsten filament. One type – dichroic halogen lamps – has a special reflector that does not reflect the infrared portion of the lamp’s output.

Halogen lamps require special fittings, and are more expensive than standard incandescent bulbs, but they last longer (up to about 2000 hours of use) and are a little more energy efficient. A 35W halogen lamp produces the same light output as a 50W standard incandescent. Low voltage halogen lamps (though these need a transformer) will further improve energy efficiency but increase cost.

Halogen lamps have a compact filament and produce a concentrated light beam that illuminates a small area, so they’re most suitable for highlighting features in the room or for task lighting.

When specifying halogen lighting:

• a whiter and brighter light is achieved with 12 Volt h
• a softer light is achieved mains-powered units
• 12 volt systems offer a range of special purpose bulbs such as wide angle, narrow beam, and colour.

Incandescent lamps

Incandescent bulbs provide light by heating a tungsten element that glows white hot – up to 95% of their energy input is radiated as heat rather than light. Their life span is short (typically about 1000 hours of use) but they are cheap. Specifying a dimmer may produce some small energy savings. In the past, lamps were often designed for effect rather than luminous efficiency.

Incandescent bulbs are best specified for infrequent or short period use. Specifying a light fitting that incorporates reflective surfaces can improve light output for the same wattage. Over time they will lose efficiency.

Light produced by an incandescent source is still considered to be the closest to natural light in colour and wavelength.

Incandescent bulbs include:

• standard frosted or clear bayonet or screw mount bulbs
• reflector bulbs that have a focused beam – these are commonly specified for spot lights or downlights.

The government has reportedly (New Zealand Herald, 21 February 2007) indicated it may phase out incandescent light bulbs by about 2010, following an Australian announcement along similar lines.

However, incandescent light bulb technology is changing. High efficiency incandescent bulbs are being developed, to deliver the same same environmental benefits as compact fluorescent lamps. And incandescent bulbs with a longer life (about 1500 hours) are being developed.

Recessed light fitting installation

Where the design incorporates recessed light fittings, the design solution must:

• allow for the dissipation of heat from around the fitting
• not compromise the performance of the insulation (specify downlights tested for NZECP 54 ratings in accordance with AS/NZS 60598 to maintain insulation levels).

For your clients

To help your clients make decisions about lighting options, refer them to www.smarterhomes.org.nz/energy/lighting.