The Lighting Design Process for London Renovations: Brief, Scheme, and Commissioning

Why Lighting Design Matters

The quality of artificial lighting determines how a room feels after dark — which, for much of the year in London, means for most of the hours during which a home is actively used. A room with poor lighting is uncomfortable regardless of the quality of its other finishes: the ceiling is too bright or too dark, shadows fall in wrong places, colours are distorted, and the atmosphere is either harsh or gloomy. A room with excellent lighting — layers of light at the right intensities, from sources positioned to graze surfaces, define focal points, and create depth — is welcoming and beautiful regardless of whether you can identify exactly why.

The investment in a competent lighting designer is typically £5,000–£15,000 for a full London townhouse — a fraction of the total project cost and one of the highest-return professional fees in the project. The cost of correcting a poorly conceived lighting scheme after completion (additional cabling, new back boxes, relocation of downlights, new switches, new dimmers) typically exceeds the lighting design fee many times over.

The Lighting Designer's Role and Appointment Timing

A residential lighting designer should be appointed at the same time as the interior designer — ideally before the architectural drawings are finalised, so that the requirements for recessed luminaires (downlights, recessed wall washers, cove lighting voids) can be incorporated into the structural and ceiling design. If the lighting designer is appointed after first fix electrical has been laid out, their input is constrained to what can be accommodated without re-cabling — a significant limitation.

The lighting designer's deliverables include: - A lighting concept document showing the intended atmosphere for each room, with reference images and rationale - A detailed lighting layout drawing showing the position of every luminaire, every switch position, and every circuit allocation - A luminaire specification schedule listing every fitting, its lumen output, beam angle, colour temperature, IP rating, and supplier - A dimming and controls specification, including which dimmers are required and how circuits are grouped - Coordination with the electrical engineer or electrician on circuit loading and switch positions - Commissioning attendance — attending site after installation to tune dimmer levels, adjust lamp angles, and confirm the scheme performs as designed

Layered Lighting: The Design Principle

Good interior lighting uses multiple layers at different heights and intensities, each serving a distinct function and all controllable independently.

Ambient lighting: The general level of illumination in a room, sufficient for safe movement and general tasks. In a well-designed residential scheme, ambient lighting is provided at a relatively low level — 50–150 lux is appropriate for living rooms and bedrooms — supplemented by task and accent lighting where higher illuminance is needed. A common mistake is to design the ambient layer alone (a grid of downlights providing 300+ lux everywhere) and omit all other layers; the result is flat, harsh, and institutional.

Task lighting: Directed light for specific activities — reading, cooking, applying makeup, working at a desk. Task lighting must be positioned to illuminate the work surface without glare to the user. Reading lights at armchairs and bedside tables, under-cabinet lighting in kitchens, mirror lighting in bathrooms, and desk lamps or integrated shelf lighting in studies are all task lighting.

Accent lighting: Light used to draw attention to a specific object or surface — a painting, a sculpture, a textured wall, a bookcase. Accent lighting is typically three to five times brighter than the ambient level at the accented object. Adjustable spotlights (on surface-mounted tracks or recessed into the ceiling with an adjustable head) are the most flexible format; picture lights (mounted above a painting and directed downward) are the traditional format for fine art.

Decorative lighting: Luminaires that are themselves visual elements — chandeliers, pendant lights, table lamps, wall sconces. These provide relatively little functional illumination but anchor the design of the room and provide visual interest. The perceived brightness of a decorative fitting at a low dimmer setting, combined with other layers at appropriate levels, produces the layered warmth that characterises an exceptional domestic interior.

Colour Temperature and CRI

Colour temperature (measured in Kelvin) determines whether artificial light appears warm or cool. For residential interiors, the correct range is 2700K–3000K:

• —2700K: The warm white associated with traditional incandescent lamps. Flattering to skin tones, warm to stone and timber, associated with comfort and relaxation. The standard for living rooms, bedrooms, dining rooms, and bathrooms.
• —3000K: Slightly cooler, with a crisper white quality. More suited to kitchens, home offices, and bathrooms where a clean, functional atmosphere is preferred. Also used in contemporary schemes with white or pale grey palettes where a 2700K source might add unwanted yellow warmth.
• —Above 3500K: Cool white to daylight tones. Appropriate for some commercial and clinical applications; not appropriate for residential interiors.

Colour rendering index (CRI) measures how accurately a light source renders colours compared to natural daylight (CRI 100 = perfect). For residential lighting, specify CRI 90 minimum throughout; CRI 95+ for areas where accurate colour rendering matters (dressing rooms, art, bathrooms). Low-CRI sources (CRI < 80) make skin look grey, distort the colours of furnishings and art, and are not appropriate for prime residential work.

Dimming and Controls

All residential lighting should be dimmable. The ability to reduce light levels — from functional working levels during the day to low, atmospheric levels in the evening — is what distinguishes a residential lighting scheme from an office installation.

Trailing edge dimmers: The correct dimmer type for LED lighting (which is the standard source type for all new residential lighting). Trailing edge dimmers (also called reverse phase dimmers) are compatible with a wider range of LED drivers than leading edge dimmers and produce less interference. Specify trailing edge throughout.

Lutron and KNX: For prime residential work, the lighting control system should be either Lutron (Caséta for simpler schemes, RadioRA or Homeworks QS for whole-house integration) or KNX (an open protocol building automation standard widely used in high-end European residential projects). Both systems allow scene setting (preset combinations of circuit levels recalled with a single button press), integration with home automation, and remote control via smartphone. Lutron Homeworks QS is particularly well regarded in the London luxury residential market — its keypads are beautifully designed, the system is reliable, and the programming flexibility is extensive.

Scene design: For each room, the lighting designer should define at least three scenes: a full bright scene (for cleaning, maximum visibility), a social scene (comfortable ambient level for entertaining or everyday use), and a low scene (for watching television, relaxing, or late evening). Additional scenes for specific activities (reading, dining) add value in living rooms and dining rooms. Scenes should be easily recalled without navigating multiple switches.

Common Specification Errors to Avoid

Recessed downlights on a regular grid: The standard approach in volume residential work produces a flat, featureless ceiling and eliminates the possibility of shadow and depth in the room. In prime residential work, downlights should be positioned to specific architectural logic — washing a wall, illuminating a work surface, defining a seating area — not on a 600mm or 900mm grid.

Single switch per room: Grouping all luminaires in a room on a single switch and dimmer eliminates the possibility of independent layer control. Each circuit (ambient, accent, decorative, task) should be independently switched and independently dimmable.

Ignoring the electrical layout at design stage: The position of back boxes, conduit routes, and consumer unit capacity must be resolved at design stage in conjunction with the lighting layout. Lighting designers who do not coordinate with the electrician produce schemes that are impractical to install.

Forgetting switch positions: Every room should have switches at every door, positioned so that the occupant can operate the lights without crossing an unlit space. Multi-way switching (controlling the same circuit from multiple positions) is standard in bedrooms (beside the door and beside the bed), hallways and landings (top and bottom of each staircase run), and reception rooms with multiple access points.