Module 5: Lighting Design – Jenniez School of African Interior Design

Learning objectives

Understand the properties of light, colour temperature, intensity and the principles of illumination.
Study how lighting affects well-being, visual comfort, mood and productivity.
Know the main lighting technologies (incandescent, fluorescent, halogen, LED and smart lighting), their characteristics and applications.
Analyse a space and choose lighting that fits its function and aesthetics.
Combine natural and artificial light through daylighting strategies, window placement and fixtures.
Create different moods using accent, task and ambient lighting.
Apply energy-efficient fixtures and controls.

Class schedule

Class activities

Revision
Watch videos
Teach module
Break
Teach the lumen calculator
Assignment

Light and lighting

Lighting design is a process: the planning of how light will be perceived in a space. It includes selecting light sources but should not start with them. What matters is not what makes the light but which objects and surfaces receive it. The key to successful lighting design is to decide what you want to light up, then work backwards to the solution.

Transmission of light

The eye and brain translate light into colour using sensors in the retina: rods, which respond to amounts of light, and cones, which respond to colour. Light travels from the primary source (the sun) to the object and then to the detector (the eye and brain). An object appears white when it reflects all wavelengths and black when it absorbs them all.

Psychological impact

The real challenge for the designer is the emotional impact of an interior, created by manipulating brightness contrast. Lighting design is not just illumination. It showcases different sections of a room.

If all surfaces receive equal light, contrast is lost, which reduces productivity and can leave people listless and depressed.
The quality of light, not the quantity, decides how people feel. People are more alert, energetic and positive on a sunny day, which brings bright highlights and crisp shadows.
First identify the activities that will take place, then decide the degree of stimulation that will reinforce them, then set the brightness contrast that will deliver it.
Some tasks benefit from high stimulation, which encourages participation, enjoyment, excitement and productivity. Others benefit from minimal contrast so people feel contented, focused and relaxed.
Brightness contrast works like background music. It affects task performance, behaviour at work and play, and contentment, and it sets an emotional tone that either supports or undermines the activity.

Low-contrast lighting

A large proportion of diffuse light and a small amount of focused light. Everything gets similar emphasis, so no hierarchy forms between foreground and background. The space is low in stimulation and behaviourally neutral. It suits easy seeing, random circulation and flexible work surfaces.

High-contrast lighting

A small proportion of diffuse light and a large amount of focused light. It makes patterns of light and shade and builds a deliberate hierarchy between foreground and background. It raises stimulation and evokes specific moods. A single spotlight on a stage is the extreme example.

Colour temperature

Colour temperature describes the characteristic colour of light, from the warm yellow of a candle flame at about 1900 K to the cool deep blue of the sky at about 10,000 K, measured in kelvin. Match the right bulb to the application.

Type	Temperature	Use
Warm white	2700 K to 3000 K	Same as a standard incandescent bulb. A direct substitute for background light in living areas, hallways and bedrooms.
Cool white	4000 K	Offices, kitchens, laundries and workshops. The cooler, bluer light makes contrast easier to see and is ideal for reading lamps.
Daylight	6000 K and above	Special applications such as retail or entertainment where a blue-white light is preferred. It gives high-quality colour rendition on the Colour Rendering Index (CRI).

Reflectance and distribution

How light bounces off walls, ceiling and floor depends on colour (dark or light), surface (matte or gloss), texture (rough or smooth) and pattern (bold or subtle). Plush, pile and textured surfaces absorb more light than smooth, glossy, reflective ones. Dark colours absorb more light than light colours. Reflective materials such as mirrors, gloss paint, polished and metallic fabrics, crystal fittings and metal surfaces can create dramatic effects in a night club or bar.

Types of light

Natural light

At the start of a project, assess the amount and direction of natural light. Know whether the space is lit or in shadow at different times of day and through the seasons. This affects textiles too: the colour and fibre of a fabric depend on how much light reaches it, when and from which direction.

Evaluating light levels and quality means noting the orientation of the building, which affects light, heat, shadows and choice of materials and finishes. Light also changes how we see colour. Morning light is clear white and afternoon light can be gold or red.

Block light

Overhangs, awnings, louvered shutters, motorised blinds, block-out blinds, fully lined curtains and upholstered screens.

Filter light

Sheer curtains, sheer blinds, cut-out screens, louvered blinds and louvered shutters.

Increase light

Enlarge windows, remove window treatments, and line window recesses with reflective surfaces.

Artificial light

Artificial light has no constraints. In a flawlessly lit room you never see the light source, even if the fitting is beautiful. You see walls and ceilings washed with a glow, lamps glowing behind softening shades, pools of light on objects and patterns of light across walls that give dimension, whimsy and mystery. Do not be afraid to experiment.

A low-hanging, shaded pendant just above eye level over a dining table gives an intimate setting. Balance it with ceiling spotlights turned to reflect off walls, so they do not shine in the eyes of diners.
Two wall lamps at eye level on either side of a bathroom or dressing-room mirror give reflected light for a small room and highlight the face.

Sources of artificial light

With the global drive to improve energy efficiency, most countries are phasing out the traditional incandescent bulb. The replacements use less energy, last longer and save money without compromising style or quality of light. The four main sources are LEDs, fluorescent, halogen and incandescent.

Source	Properties and uses
LED (light-emitting diode)	Energy efficient with very low heat output. Extremely long lasting (50,000 to 100,000 hours). Expensive to buy, and the price reflects quality. Available as downlights, spotlights, globe bulbs, decorative candle bulbs, wall lights, stair footlights and flexible or rigid coloured strip lights for indoors or out. Warm white, cool white or daylight. Dimmable.
Fluorescent	Low energy use and long life (6,000 to 15,000 hours). Good for ambient or mood lighting, in warm white, cool white or daylight. Fits conventional bayonet or screw sockets and can replace incandescent bulbs in most fittings. Standard CFLs do not work on a dimmer circuit; only dimmable spiral CFLs do. They take time to reach full brightness, so are not suited to toilets and bathrooms where instant light is needed. New-generation fluorescent can light the back of a translucent screen or the inside of a coffer evenly to give a convincing soft daylight effect.
Halogen	Ideal for spot and task lighting over work surfaces because the built-in reflector gives a narrow beam. Used for accent and mood lighting in dining and living areas. The narrow beam goes down to the floor rather than reflecting off walls and ceiling, so it can make a space look smaller. Dimmable. CRI of 100, so colour and texture look true. Recessed and flush-mounted halogen ceiling lights need a 12 V transformer and a ceiling cavity of at least 15 cm. Clear halogen can be bright and piercing, so shade it or bounce it off another surface, and use it together with other fittings to keep a soft, even level.
New-generation halogen	A direct replacement for the standard incandescent lamp that lasts about twice as long and is about 30% more efficient. Costs more. Works with dimmers, sensors and electronic switches and gives instant light.
Specialist halogen	Lamp bulbs for task lamps and candle bulbs for decorative lighting. Oils from your fingers shorten the life of the bulb, so avoid touching the glass when replacing.
Incandescent	Long the dominant source in older homes. Warm, yellowish and flattering to the complexion, ideal for background lighting, with a narrow pool of light so watch for hot spots. The least efficient source: most energy leaves as heat. Replace with warm white CFLs or new-generation halogen to keep the colour tone and gain efficiency.

Types of artificial light

Ambient lighting

The primary choice, around which all others fall in. It provides background lighting for safety and general activity and supplements natural light. It is usually a fixed, dimmable pendant in the centre of the room or a number of recessed ceiling lights that diffuse light over walls and ceilings. On its own it is indirect and lacks interest, so combine it with uplights, wall sconces and floor or table lamps to produce light and shade.

Task lighting

A concentrated beam of bright light on a surface for a specific job: food preparation, shaving, working, reading or playing an instrument. Fixtures are either installed (hardwired, such as pendants over desks or kitchen work areas, wall sconces or floor-level stair lights) or mobile (desk and floor lamps that plug in). The source should be hidden to avoid glare and sit in front of or beside the person so shadows do not fall on the work.

Accent lighting

Targets decorative features for visual effect: artwork, accessories, shelves, collections, stairs and architectural features. It can be set into floor, walls or ceiling. Spotlights are common, but wall lights, downlights and lamps also work. Dark walls absorb light from above, so use wall lights that shine up and reflect off a light ceiling. Dimmers help set the atmosphere.

Keep ambient light discreet

Ambient light should be relatively low level so it does not compete with task and accent lighting.

Light levels and lighting calculation

Different spaces need different light levels, which is why using several lighting effects in one space is advisable. Lighting must be worked out on a plan before it is installed, even if the fixtures need no electrical work. A lighting plan sits directly over the floor plan and carries a legend or key of electrical symbols.

Calculating the total light needed is the quantitative side of lighting. The lumen method is the most common: establish the intended use of the space, then measure its area.

Term	Meaning
Lumen	The total quantity of visible light a source emits, also called light output or brightness. A standard 100 W incandescent bulb produces about 1,500 to 1,700 lumens.
Lux	Illuminance: lumens per square metre.
Efficacy	Lumens produced per watt consumed. The higher the number, the more efficient the bulb.
Watt	Not a measure of brightness but of how much electricity the bulb uses to reach its claimed brightness. Each source has a different lumen-per-watt ratio.
Wattage equivalence	A 100 W incandescent gives about 1,500 lumens, and so does a 10 W LED.

As a guide, an average 23 m² (250 sq ft) room needs roughly 2,500 to 5,000 lumens as its primary light source, about 110 to 215 lumens per square metre. Over a dining table you want about 325 lumens per square metre. A table of 1.8 × 0.9 m is about 1.7 m², so around 540 lumens. These figures assume typical conditions and 2.4 m (8 ft) ceilings. With especially dark walls and furniture, or with shaded fixtures, add roughly 110 lumens per square metre. Personal preference matters: if you like a room bright, add 10 to 20%. For most spaces, aim high and install dimmers.

Recommended lux levels: residential

Space	Lux	Notes
Living room (general)	100 to 200	Ambient, relaxing light
Living room (reading, tasks)	300 to 500	Task lighting near seating
Dining room	200 to 300	Higher over the table itself
Kitchen (general)	300 to 500	Ambient
Kitchen (countertop, task)	500 to 750	Preparation and cooking zones
Bedroom (general)	100 to 150	Ambient
Bedroom (reading)	300 to 500	Bedside task lighting
Bathroom (general)	200 to 300	Ambient
Bathroom (mirror, vanity)	500	Grooming tasks
Home office or study	500	Desk-level task light
Hallway or stairs	100 to 150	Circulation and safety
Closet or storage	100	Basic visibility
Garage	100 to 300	Higher if used as a workshop

Recommended lux levels: commercial

Space	Lux	Notes
Reception or lobby	200 to 300	Welcoming, moderate
General office (open plan)	300 to 500	Standard task lighting
Executive office	300 to 500	Sometimes with accent lighting
Conference or meeting room	300 to 500	Adjustable for presentations
Retail (general)	300 to 500	Ambient store lighting
Retail (display, feature areas)	750 to 1,500	Highlighting products
Supermarket	500 to 750	Even, bright coverage
Restaurant (dining area)	100 to 300	Mood-dependent, often dimmable
Restaurant (kitchen)	500 to 750	Food preparation, safety
Hotel guest room	100 to 300	Like a residential bedroom
Hotel corridor	100 to 150	Circulation
Classroom	300 to 500	Reading and writing tasks
Library (reading area)	300 to 500	Task-focused
Hospital (general ward)	100 to 300	Ambient patient care
Hospital (operating room)	1,000 to 20,000+	Surgical task lighting, highly specialised
Warehouse (general)	100 to 200	Storage and circulation
Warehouse (picking, packing)	300 to 500	Task areas
Industrial workshop	300 to 750	Depends on the precision of the work
Parking garage	50 to 100	Circulation and security

Simple formulas

1. Total lumens requiredTotal lumens = Area (m²) × Required lux

Area is length × width. Example: a 4 m × 5 m office is 20 m² and needs 300 lux, so 20 × 300 = 6,000 lumens. Take the lux value from the tables above.

2. Number of fixtures or bulbsNumber of fixtures = Total lumens required ÷ Lumens per fixture

Example: 6,000 lumens needed and one LED bulb gives 800 lumens, so 6,000 ÷ 800 = 7.5, which rounds up to 8 bulbs. Always round up.

3. Wattage and energy use

Watts per fixture = Lumens of bulb ÷ Efficacy (lm/W)
Total watts = Number of fixtures × Watts per fixture
Energy (kWh) = Total watts × Hours used per day ÷ 1000

Example: 8 LED bulbs at 10 W each is 80 W. Used 5 hours a day, that is (80 × 5) ÷ 1000 = 0.4 kWh per day.

Bulb type	Typical efficacy (lm/W)
Incandescent	10 to 17
CFL	50 to 70
LED	80 to 100+

4. Placement and distribution of fixtures

Spacing between fixtures = SHR × Mounting height
Fixtures per row = Room length ÷ Spacing
Number of rows = Room width ÷ Spacing
Wall offset = Spacing ÷ 2

The spacing-to-height ratio (SHR) is typically 1 to 1.5, so check the manufacturer’s spec sheet. Mounting height is measured from the fixture to the work plane, usually about 0.85 m above the floor. Example: mounting height 2.5 m and SHR 1.5 give spacing of 3.75 m. In an 8 m × 6 m room that is about 2 fixtures per row and 2 rows, so about 4 fixtures. The distance from the wall to the first fixture is half the spacing, which prevents dark corners. Cross-check with the lumen method.

Light distribution. After you know the lumens a space needs, decide the lighting sources and fixtures, and the lumen output of each fixture.

Improving energy efficiency

Switches. Locate switches at the entry and exit points of a room. Use two- or three-way circuits where a room has several entrances, and put switches at the top and bottom of a stairwell. Give each lighting installation its own control, since one switch for all lights wastes energy. Put task and accent switches next to the task area so they are used only when needed.
Sensors. Movement sensors turn lights on when someone enters and off when they leave. There are two types: motion detectors and presence detectors.
Dimmers. Dimmable circuits and layering several kinds of light change the mood of a room. Dimmers also save energy and extend bulb life by reducing output.

Lighting your home

The front door

The first impression. A well-lit path leads visitors from the street or driveway to the door. Choose fittings that suit the architectural style, keep light around the door brighter than the surrounding landscape lighting, add a feature such as a planter to make it welcoming, and consider security lighting as a deterrent.

Entrance and hallway

A restricted area with little room for furniture, so use lighting for visual impact. Use ceiling or wall lights for ambient light, uplights for drama and spotlights on artwork. A large pendant or chandelier suits a void or stairwell. A narrow console with a table lamp gives soft warm light. Put a switch near the front door, and use a dimmer to help the eye adapt.

Living rooms

Many activities happen here, so lighting must be practical, attractive and flexible. Dimmed recessed downlights give a softer atmosphere. Add floor lamps, table lamps and uplights for general light, task lighting for reading and hobbies, and accent lights for artwork. A variety of lights prevents monotony.

Dining room

Good light is essential for enjoying food. A pendant gives a focal point and a broad spread of light over the table, but its shape and height must avoid glare and not block conversation. Dim it for intimacy. Table lamps and low-wattage uplighters soften the evening mood.

Kitchen

The main task area, often open plan. Plan task lighting over benches first, then ambient light. Use adjustable halogen spots to avoid working in your own shadow, downlights or pendants over an island, and fluorescent strips in pantries and under wall cupboards. Use accent light on splashbacks and under island benches. Good colour rendering is essential for food preparation. Lights must meet the electrical code for a damp area.

Bedroom

A restful environment for sleep. Use soft ambient light for relaxing and watching TV, and task lighting for reading, writing and make-up. Bedside lamps and dimmable wall lights or uplights behind the bed give background light. A children’s room can have a small shaded low-wattage lamp or a plug-in night light.

Stairs

Light stairs well for safety and to avoid hazardous shadows. Small lights recessed into the wall or treads define the path and make a feature of the stairwell. Pendants from the first floor and wall lights also work.

Bathrooms: lighting and electrical safety

Bathrooms are wet areas, so the safety of light fittings is paramount because electricity and water are close together.

Fixtures within a set distance of a shower, bath or basin must be sealed or closed to prevent water and steam damaging the wiring.
An Ingress Protection (IP) rating shows suitability. In IP54, the first digit (5) means protected against dust and the second (4) means protected against splashing. The higher the number, the better the protection.
Control ambient light with a dimmer for a relaxing bath.
Lights on either side of the mirror give even, glare-free light for shaving or make-up. A light above the mirror is not flattering because it casts shadows on the lower face.
Residual current devices (RCDs) are used in bathrooms in place of a standard power outlet. They are a legal requirement in bathrooms and other damp areas in new homes, or where a new circuit from the switchboard is added to an existing home.
Extraction fans are essential in wet areas (kitchen, bathroom, laundry). They must vent to the outside through the ceiling or an outside wall, so damp air does not recirculate and cause mildew.

Lighting terms and definitions

Term	Definition
Ballast	Electrical or electronic component required to start and operate fluorescent lamps.
CRI	Colour Rendering Index, on a scale of 1 to 100 with 100 ideal. The ability of a light source to render the colour of an object accurately compared with natural light.
Colour temperature	The warmth or coolness of white light, measured on the Kelvin scale.
Cove lighting	Lighting, usually fluorescent or LED, built into a shelf or ledge high on a wall to illuminate the ceiling.
Dimmer	A control that lowers the light level to change the mood. It also saves energy and extends bulb life.
Gimbal lighting	An adjustable ring that holds a halogen or LED downlight by its rim so the direction of light can change.
GPO	General Purpose Outlet or General Power Outlet: what you may know as a power point. It can only be installed or maintained by an electrician.
Hardwired	A fixture permanently connected to an electrical source, with no visible cord or plug.
Heat rating	Recessed downlights and surface-mounted fixtures must pass heat tests so they do not affect combustible ceiling materials. This limits the maximum safe wattage.
IP rating	Ingress Protection. The first digit shows how dust proof a fitting is and the second how waterproof. Important for wet areas and outdoor lighting.
Kelvin scale	Colour temperature scale. Lower ratings are warm and yellow, higher ratings are cooler and bluer.
Kilowatt hour (kWh)	A unit of electrical energy. One kWh is 1000 watts used for one hour.
Lumens	The amount of light a bulb produces.
Luminaire	A complete lighting unit including lamp, housing, ballast, sockets and other necessary components.
Lux	The unit of illuminance, in lumens per square metre.
Recessed downlight	A circular or square fixture set into the ceiling that concentrates light downward.
Retrofit	Replacing existing fixtures with new technology that improves efficiency or safety.
Three-way switch	Operates a fixture from two locations.
Transformer	Converts one voltage to another. Many halogen ceiling fixtures need one.
Wall lighting	Lighting directed onto a wall to emphasise the plane, enhance texture or bounce light back into the room. Brighter walls generally make a room seem more spacious.
Wall washing	A technique that washes a wall evenly with light.
Watt	A unit of electrical power.
Wattage	The electricity a bulb consumes. For devices, the maximum watts they are designed to deliver or control.

Assignment: lighting and electrical plan

Choose one of two options. Imagine your lighting plan sitting directly over your floor plan.

Option A. Continue from the plan you created in Assignment Four and draw a plan for lighting and other electrical equipment.
Option B. An architectural plan is provided so you can follow a real workflow for lighting system design. Draw a lighting plan for the sample (100 marks).

Plan power sockets for all kitchen appliances and white goods (fridge, microwave, stove, dishwasher) and for entertainment and computer equipment.
Research what technology and appliances are available in your country and the constraints and requirements for installing them.
The existing house is over 60 years old and has its original electrical work and switching. Show your fixtures, outlets, switches, dimmers, wiring and anything else your electrician needs.
You do not need to include flooring or furniture, but label every room and include a lighting legend or key.
Draw by hand, scan and upload as a JPEG or PDF, or draw digitally.