- How many lumens for each room
- Number of lamps needed for a small room with light walls
- Amount of light depending on the room to be illuminated
How much light do we need? It depends on the place, our age and our habits. explanations:
How many lumens for each room
The number of lumens emitted by a lamp is clearly indicated on the packaging (this is the amount of light emitted per second). But to estimate the total number of lamps needed for general lighting, we use the following formula:
• The number of lux depends on the room
• The luminaire efficiency is given by the manufacturer. It should normally appear in the luminaire manual (it is usually between 0.7 and 0.8).
• The reflection factor depends on the color of the walls according to whether they are raw plaster (0.85), painted white (0.7), light colored (0.6), light gray (0.5), light wood (0, 4), red brick (0.2) or slate gray (0.1).
Number of lamps needed for a small room with light walls
For example: in a 12 m² white painted room (reflection factor of 0.7), if you want to have 100 lux, you need luminaires with 0.8 efficiency. Demonstration:
Calculation of the total power of light:
In our example, the formula is: 100 x 12 x 1 / 0.7 x 1 / 0.8 =
The number of lamps needed according to the type of bulb is:- With incandescent having a yield of 15 lm / W, it will be necessary to install 143 W.
Three 60 W lamps
- With halogens displaying a yield of 25 lm / W, it will be necessary to install 86 W.
Two 40 W lamps
- With compact fluorescents with a performance of 60 lm / W, it will be necessary to install 36 W.
three 12 W lamps
Amount of light depending on the room to be illuminated
The recommendations of the French Association of Lighting:
The French Association of Lighting (AFE) recommends to respect levels of luminous intensity according to the activity (the unit of measure is the lumen / m², more generally called lux).
|Piece||General lighting||Spot lighting|
|100 lux||100 lux|
|Staircase||200 lux||300 lux|
|Stay||200 lux||300 lux|
(as a reader)
|100 lux||250 lux|
(in front of the dressing room)
|300 lux||500 lux|
|Cooked||300 lux||425 lux|
(on work plan)
|Bathroom||300 lux||500 lux|
(in front of mirror)
|Garage||100 lux||400 lux|
(on DIY workbench)
In comparison, a very sunny summer day is around 100,000 lux, while a covered summer day varies from 30,000 to 40,000 lux.