Artificial Lighting (Leaving Cert Construction Studies): Revision Notes

Artificial lighting

Introduction to artificial lighting

Proper lighting planning is essential for any dwelling. You need to consider both the types of lights you'll use and how you'll control them as you move between rooms. Safety is particularly important in hazardous areas like stairs, especially at night.

Artificial lighting systems can be organised into two main categories:

Architectural fittings are permanent fixtures planned during construction. These include coving lights, pendant lights, and recessed lights that are built into the structure.

Non-architectural fittings are moveable fixtures like table lamps and floor lamps. These can be repositioned as needed and aren't permanently installed.

How artificial lighting works

Incandescence occurs when an object becomes so hot that it glows and emits light. The heating element inside a traditional light bulb works this way.

Luminescence produces light through chemical reactions, electrical energy, or subatomic motion rather than heat. This method is generally more energy-efficient.

Types of artificial lighting

General lighting service (GLS) lamps

The traditional light bulb works by passing electric current through a tungsten metal filament until it glows. The filament sits inside a glass casing filled with vacuum or partial vacuum to prevent overheating.

GLS lamps are incandescent, meaning they create light through heat. However, this makes them very inefficient - typically 90% of their energy becomes heat rather than light. The glass casing can be made in different shapes, sizes, and colours, and may be frosted to soften the light output.

Halogen lamps

Halogen lamps contain special gases (usually iodine or bromine) within the glass envelope alongside the tungsten filament. This gas extends the filament's life and allows the lamp to operate at much higher temperatures.

The higher temperature creates a bluish-white light with better colour quality. However, this also makes halogen lamps extremely hot during operation, creating fire and burn hazards. Strict safety guidelines govern their installation, particularly for recessed ceiling fittings.

Halogen lamps are available in both high-voltage and low-voltage versions, though the lamp's wattage has the greatest impact on energy consumption. Their small size makes them useful in compact spaces like under kitchen units.

Fluorescent tubes

Fluorescent lighting works completely differently from incandescent bulbs. The tubes contain inert gas (commonly argon or mercury vapour), and when electricity passes through this gas, it produces light.

The inside of the tube is coated with phosphor, which absorbs the initial light and then glows (fluoresces) to produce the visible light output. This process creates light rather than heat, making fluorescent lamps much more efficient than incandescent alternatives.

Compact fluorescent lamps (CFLs)

CFLs operate using the same principles and chemicals as standard fluorescent tubes. The main difference is their curved shape rather than straight design. This compact form allows them to replace traditional GLS bulbs in standard light fittings.

CFLs are becoming popular replacements for common light bulbs because they're significantly more energy-efficient and last much longer than tungsten-filament bulbs. They can be fitted with either screw or bayonet connections.

Light-emitting diodes (LEDs)

LEDs are small semiconductor devices commonly seen as indicator lights on electronic equipment - like the red light on televisions. They consist of two terminals (positive and negative), and when current flows between them, photons of light are produced.

LEDs offer several significant advantages:

• Extremely long lifespan of up to 100,000 hours
• Very quick to reach full brightness when switched on
• Can be dimmed or brightened as required
• Available in many colours and sizes

The main disadvantage is cost - high-power LED lighting can be five times more expensive than fluorescent alternatives.

Comparing lighting efficiency

Fluorescent lighting is remarkably more efficient than incandescent lighting. This efficiency comes from producing light rather than heat, unlike incandescent bulbs where most energy becomes wasted heat rather than useful illumination.

Key lamp characteristics

Different lamp types have distinct performance characteristics:

Life expectancy varies dramatically - from $1,000$-$2,000$ hours for GLS lamps up to 100,000 hours for LEDs. Fluorescent types typically last $6,000$-$8,000$ hours.

Energy efficiency is measured in lumens per watt - the higher the number, the more light output per unit of electricity consumed. LEDs typically achieve $30$-$35$ lumens per watt, while traditional GLS lamps only manage $12$-$18$.

Colour temperature affects the appearance of the light, measured in degrees Kelvin. Higher numbers produce cooler (bluer) light, while lower numbers give warmer (yellower) tones.

Power consumption ranges from as little as $10$ watts for some LEDs up to $150$ watts for high-power GLS bulbs.

Luminaires

A luminaire is the complete lighting unit that houses and operates the lamp. It includes several essential components working together:

• The lamp itself (bulb or tube)
• Socket and mounting parts to hold the lamp securely
• Electrical wiring connecting to the power source
• Reflector to direct and distribute light effectively
• For fluorescent fixtures, lenses or louvres to reduce glare and redirect light

Luminaires can be either portable (like table and floor lamps) or permanently mounted to ceilings and walls. They serve the crucial function of not just holding the lamp, but controlling how the light is distributed throughout the space.