Complete guide
Indirect lighting – everything you need to know
What indirect lighting is, how it works and which three dimensions decide the result. Structures, components, costs and the seven mistakes that ruin the result.
What indirect lighting is
Indirect lighting means lighting where the light source is hidden and the light is directed to reflect off the building’s surfaces – the ceiling, walls or floor – before it reaches people. The light source is never directly visible.
The result is glare-free, soft and even light that fills the whole room without hot spots or sharp shadows. It is the opposite of direct lighting – spotlights, pendants and panel lights – where light goes straight into the eyes or onto the work surface.
How indirect lighting works
The LED strip is installed hidden in a bulkhead – a light cove, a dropped ceiling or a profile – and aimed at a reflecting surface. The light hits the surface first and reflects from it as broad, soft light into the room. In practice, the ceiling surface is the luminaire, not the strip.
This leads to the most important limitation of indirect lighting: the colour of the reflecting surface decides how much light ends up in the room. The same strip gives twice the result on a white ceiling compared with a dark one.
| Reflecting surface | Light into the room | Effect on sizing |
|---|---|---|
| White matt ceiling | 80-85 % | Basic sizing is enough |
| Light grey ceiling | 60-70 % | Add about 20 % more power |
| Wood panelling, pine | 40-55 % | Almost double the power |
| Dark panelling or concrete | 20-40 % | Indirect general lighting does not work |
Reflectance values and their effect on the power required
The single most important thing
Indirect lighting only works on a light reflecting surface. A dark ceiling does not reflect enough at any strip power. If the ceiling is dark or wood-panelled, there are three options: paint the ceiling a light colour, increase the strip power significantly, or give up on indirect general lighting and use it as mood lighting.
The colour of the ceiling is also the variable many people overlook at the design stage. The sizing calculator takes it into account.
Structures – three main types
Choosing a structure is not a matter of taste but follows from the constraints: is a renovation under way, how much ceiling height is available, and does the result need to be invisible.
1. Plasterboard bulkhead – light cove or dropped ceiling
The most common and the best result. A bulkhead built from timber framing and plasterboard at the edge of the ceiling or wall. The LED strip is completely hidden, the glare shield is sized and the driver sits inside the bulkhead behind an access hatch. Requires building work before the plasterboard goes up.
- Space required: from 50 mm with a low profile, typically 100-250 mm
- Building work: framing, plasterboarding, filling, painting
- Suits: new builds and renovations where the ceiling is open
- Light cove – dimensions and installation steps → · Dropped ceiling → · Plasterboard bulkhead →
2. Surface-mounted profile – retrofit
An aluminium profile is screwed directly onto a finished wall or ceiling. No building work, no painting. The slimmest profile takes 18 mm. This is the only structure that can be done in a lived-in home in a single day.
- Space required: 18-33 mm depending on the model
- Building work: screwing and a cable duct
- Suits: finished homes, rented flats, bathrooms with IP65 strip
- Retrofit indirect lighting → · Low ceilings →
3. Recessed into furniture
An LED strip recessed into a groove in furniture – a bookcase, TV unit, kitchen wall cabinet, display cabinet. Furniture accent or targeted mood lighting. The smallest-scale solution, and it does not replace room-level general lighting.
- Space required: 10-25 mm, a recessed profile needs a groove of about 12 mm
- Building work: routing or a groove in the furniture
- Furniture → · Kickboards →
All six structures with dimensions and construction drawings: All structures and construction details.
Sizing basics
Three dimensions decide the result: bulkhead height, glare shield length and the strip’s distance from the edge. Everything else follows from these.
| Dimension | Value | Explanation |
|---|---|---|
| Glare shield | 30-50 mm or 15-25 mm | Depends on the strip’s distance from the lip: 40-60 mm back → 30-50 mm lip. Right behind the lip → 15-25 mm, light is cut on the viewer’s side. Always check from a seated position. |
| Strip distance from back wall | ≥ 30 mm | The light needs room to spread before the ceiling |
| Opening width | ≥ 1.5 × distance | A narrower opening restricts the beam too much |
| Driver load | max 80 % | A 100 W driver takes at most 80 W of strip |
| Max length from one end | 7-8 m | Longer runs suffer voltage drop – feed from both ends |
Five sizing limits
The lip height depends on how far the strip is from the lip – there is no single formula. The only reliable method is to sit where the sofa will be and see whether the strip is visible – in the bedroom the same test is done lying down. Do it before the plasterboard goes up.
Amount of light and ceiling reflectance calculated: How much light · Glare shield · Driver sizing · Sizing calculator.
Suits every room – in different ways
The role of indirect light changes with the room. In living spaces it is general lighting, in workspaces a base level with accent lighting on top, and in the sauna or on a kickboard purely mood lighting.
Living room14.4 W/m · 2700-3000 K · dimmable
Bedroom7.2-14.4 W/m · 2700 K · lying-down test
Kitchen14.4-17 W/m · 3000-3500 K · + worktop lighting
BathroomIP65 · 14.4 W/m · separate mirror light
All 14 rooms with sizing values: Rooms.
What products you need
Indirect lighting always needs at least three components: the strip, the profile and the driver. The controller, i.e. a dimmer, is the fourth, and it is strongly recommended – without it the room has only one light level.
| Component | Requirement | Typical price |
|---|---|---|
| LED strip | 14.4 W/m for general lighting, CRI at least 95. Dotless COB in a profile under 20 mm, dense SMD in deeper ones. | €15-45/m |
| Aluminium profile | Required for strips over 10 W/m – cooling and light control. Also gives a straight line. | €8-25/m |
| LED driver | 24 V, dimmable, max 80 % load. In an accessible place. | €40-150 each |
| Controller or Zigbee | Recommended. Zigbee is the only workable retrofit for dimming. | €30-120 each |
Four components and their requirements
Choosing components in detail: LED strips · Aluminium profiles · LED drivers · COB vs SMD · Dimming and control.
All components → LedStore
The seven most common mistakes
These seven repeat from project to project. The first six can be fixed at the design stage for free – in a finished structure each one means demolition.
01Dark ceiling – indirect light does not work
A dark ceiling reflects only 20-40 % of the light. The result is dim regardless of strip power, because the light is absorbed by the surface before it reaches the room. A light ceiling surface is the first prerequisite of indirect lighting, not a finishing detail.
02Glare shield too short
The strip is directly visible from a seated position even if it is hidden when standing. The lip needs to be 30-50 mm when the strip sits 40-60 mm back, or 15-25 mm when it sits right behind the lip – but the only reliable check is to sit in place and look. Do it before the plasterboard goes up.
03Driver plastered in
The driver sealed inside the plasterboard without an access hatch. It overheats and typically fails within 1-3 years, and replacing it means opening the ceiling. The driver is the part that fails first – always an access hatch or placement outside the structure.
04Mood-level power as general lighting
A 7.2 W/m strip as general lighting produces 30-50 lux on the floor, which is enough for mood but not for lighting. General lighting needs 14.4 W/m on a white ceiling, or 17 W/m on wood panelling and in high rooms.
05SMD strip in a low profile
In a profile under 20 mm, the dots of an SMD strip do not have time to blend before the diffuser, and a row of dots shows on the ceiling. Dotless COB is the only workable choice for a profile under 20 mm. In deeper ones, dense SMD gives the same result for less.
06Dimming decided afterwards
The cabling is in and the plasterboard is up. Wired TRIAC or 0-10 V needs a control wire, and afterwards that means opening the ceiling. Zigbee is the only workable retrofit, but it is an extra device and an extra cost.
07Over 8 metres from one end
Voltage drop makes the far end of the run noticeably dimmer, and the difference shows immediately when the same strip continues around the wall. For runs over 7-8 metres: feed from both ends or add a second driver.
What indirect lighting costs
Materials are €40-60/m including strip and profile. The decisive difference comes from building work: a surface-mounted profile needs none, a plasterboard bulkhead needs framing, plasterboarding, filling and painting.
| Project | Materials | Electrical work | Building work | Total |
|---|---|---|---|---|
| One wall, retrofit | €80-180 | 1-2 h | – | €160-360 |
| Living room, light cove | €400-800 | 3-5 h | €600-1200 | €1200-2500 |
| Whole floor | €900-2000 | 6-10 h | €1500-3000 | €2900-5900 |
Total costs by project scope
Many countries offer tax relief on installation labour – check your local rules. Detailed cost guide →
Frequently asked questions
Can indirect light be added to a finished home?
Yes. A surface-mounted profile is screwed onto a finished wall or ceiling and needs no building work or painting. The slimmest profile takes 18 mm. In a finished room it installs in 2-4 hours.
Is indirect light enough on its own?
In living spaces yes, if the sizing is right: 14.4 W/m and a light ceiling. In workspaces no – 500 lux of task lighting would be economically absurd with indirect light, because the ceiling surface wastes about 75 % of the light. Layered lighting, i.e. indirect general lighting and accent lighting together, is almost always better than indirect alone, which is even but flat.
Do I need an electrician?
Cabling and junction boxes require an electrician. A plug-in driver is a DIY installation, so a retrofit into a socket can be done yourself. Bathrooms and saunas are always an electrician’s job.
Which colour temperature suits a living room?
2700-3000 K warm white. A CCT strip, i.e. tunable white, is the best choice if the room is also used for work – warm in the evening, neutral during the day.
Can dimming be added afterwards?
With a Zigbee driver, yes: you replace the driver and add a battery push-button. Wired dimming, i.e. TRIAC or 0-10 V, needs a control wire that has to be run at the installation stage – afterwards it means opening the structure.
How long does an LED strip last?
A quality strip lasts 50 000 hours, about 17 years at eight hours a day. Lifetime is shortened by overloading, i.e. more than 80 % of the driver’s power, and by poor cooling, i.e. no profile.
How much ceiling height does indirect lighting take?
At minimum 12 mm with the slimmest surface-mounted profile. A plasterboard bulkhead takes 50-61 mm and a dropped ceiling 100-200 mm. The slimmest plaster-in solution leaves the light surface 7.5 mm from the finished ceiling.
At what stage of a renovation is indirect lighting decided?
At the same time as the ceiling structure, before the plasterboard goes up. Four things need to be locked in: structure depth, profile position, cable routes and driver location. They cannot be reached once the board is fitted.
Profiilit tähän rakenteeseen
Profiilit jälkiasennukseen
Pinta-asennettavat profiilit ruuvataan valmiiseen seinään tai kattoon. Ei purkua, ei kipsitöitä, ei tasoitusta – asennus valmistuu tunneissa.
Profile-INDIRECT-wall-2m · valkoinen tai musta
Profile-INDIRECT-1-W-3m
profile-INDIRECT-2-3m · harjattu tai musta
profile-INDIRECT-3-W · 2,5 m tai 3 m
Profile-curtain-DECO-W-2m
Profile-floor-molding-3m
profile-shelf-EDGE-W-3m
Profile-indirect-molding-stairs-3m
Hinnat sisältävät ALV 25,5 % ja ovat LedStore.fi:n voimassa olevia hintoja. Profiilit sisältävät opaalikannen ja päätypalat; LED-nauha tilataan erikseen.
Toteutettuja kohteita
Epäsuora valo olohuoneessa
Alaslasku, verhoprofiili, kattopalkki ja korkea tila – viisi tapaa toteuttaa olohuoneen epäsuora valo.
Kuvat: LedStore.fi toteutetuista kohteista.