Recessed downlights are a versatile light source for homes, hospitals, hospitality settings, offices, schools, or retail environments. They can fulfill any of the three main lighting roles: general lighting, task lighting, and accent lighting.
This article advises on how many fittings you’d need for any given space, and discusses some of the issues associated with recessed downlights.
So Where Do You Start?
Before shopping for downlights, it’s useful to note a few details:
- What is the size of the space?
- What is the height of the ceiling?
- Is it an open plan area?
- What is the room’s purpose?
This information enables you to calculate how many lights you need and what type.
How Many Downlights Do I Need?
A simple method for estimating the number of downlights required is as follows:
- Step 1: Multiply the room’s width by its depth to ascertain the square footage.
- Step 2: Multiply the square footage by 1.5 to give the total wattage needed in the room. For example, a 15 x 10 foot room is 150 square feet in size; multiplying this figure by 1.5 gives you a total of 225 watts.
- Step 3: Divide the total wattage previously calculated (225 in our example) by your chosen bulb wattage to work out how many fittings you need. A 6 x 40W installation would be sufficient in our theoretical 150 square foot room.
Task lighting areas need more light. To account for this, you can multiply the footage by 2.5 rather than the 1.5 figure used above.
Divide an open plan space into areas to make your calculations. If using LED downlights, use their equivalent wattage in these sums.
This is intended as a guideline only. An experienced installer will offer tailored advice.
The coverage area of a downlight depends on the beam angle of the light source and the height of the ceiling. A flood beam spotlight naturally lights a greater surface area than a narrow beam, but with less intensity (assuming the two emit an identical amount of light in lumens).
Recessed downlights are generally positioned 1.5 to 2 ft. away from walls with a space of 3 to 4 feet between each light. Dividing the ceiling height by two is a way of gauging how much space to leave between each downlight. Thus, if your ceiling is 8 foot high, place your lights 4 feet apart.
Strict guidelines exist regarding how intense light should be in different areas of a workplace. Light intensity as it hits a surface is measured in units of lux (abbreviated to lx). Lux meters or online lumens-to-lux calculators can be used to measure or estimate this adequacy of light.
Lux measurements are governed by EN 12464-1 regulations. For example, an office workstation needs a minimum light intensity of 500 lx, foyers or entrance halls need 200 lx, corridors need up to 200 lx, stairs or lifts need 100 lx, and so on. Similarly, in the home, a task lighting area such as a kitchen worktop benefits from at least 300 lx, whereas a living room needs only 150 to 200 lx.
Beam Angles and Fire Ratings
A narrow spot beam gives an intense light for task applications and is useful for highlighting small display items. Choose a recessed downlight with a flood beam for general lighting. Those with an adjustable head can be aimed at pale-coloured walls or cupboards to spread light.
Any fire-rated ceiling, which is usually one beneath an occupied floor, needs a fire-rated downlight to be installed. This prevents an early ceiling collapse in the event of a fire, allowing crucial evacuation time for anyone above.
Choose dimmable downlights to create mood and save energy. Contrasting areas of light and dark invariably add atmosphere to a room. You might use dimmable downlights for general lighting, turning them down for intimate effect while giving greater emphasis to floor lamps, table lamps, picture lights or wall lights.
For more useful information, check out our Lighting Advice section.