The most common question is : How big is the wattage and how many light bulbs are needed in the room?
A. Basic Concepts
- Lumen = Lighting power units produced from 1 source
Generally the Lumen value is listed on the lamp specifications
- Lux = lighting power unit in the illuminated plane. Lux was used as the end result which was given the light at the illuminated point
Example : if the value of 100 Lux is calculated in one small point, it will show a very bright light. But if the point is made wider or biased wider then the Lux value will decrease because the end result of the lighting intensity is dimmer with refraction
- The unit used to calculate lamp requirements = Lumen & Lux. So easily, lumens are the level of lighting produced by lights, while lux is lighting in the illuminated plane
For example : 7 Watt brand A lamp that produces 560 lumen if installed in a toilet room measuring x length = 1.5 x 1.5 M² with a standard height of 3 meters will look very bright. This means that the lux value is large. But if the same lamp is installed in a room measuring 6 x 6 M² with the same height then the light will look less bright. In this case the lux value decreases
1 Lux = 1 Lumen m²
B. Determine the amount of light needed in a room
In determining this amount of light, one of the guidelines that can be used is the SNI-03-6197-2000 table where there are lux standards needed for each room.
| Room | Lighting level (Lux) | Color rendering group | Color Temp | |||
|---|---|---|---|---|---|---|
| Warm White <3300K |
Cool White 3300K - 5300K |
Daylight >5300K |
||||
| Residence : | ||||||
| Terrace | 60 | 1 Or 2 | • | • | ||
| Living Room | 120 ˜ 150 | 1 Or 2 | • | |||
| Dinning Room | 120 ˜ 250 | 1 Or 2 | • | |||
| Workroom | 120 ˜ 250 | 1 | • | • | ||
| Bedroom | 120 ˜ 250 | 1 Or 2 | • | • | ||
| Bathroom | 250 | 1 Or 2 | • | • | ||
| Kitchen | 250 | 1 Or 2 | • | • | ||
| Garage | 60 | 3 Or 4 | • | • | ||
| Offices : | ||||||
| Director's Room | 350 | 1 Or 2 | • | • | ||
| Workroom | 350 | 1 Or 2 | • | • | ||
| Computer Room | 350 | 1 Or 2 | • | • | ||
| Metting Room | 300 | 1 | • | • | ||
| Drawing Room | 750 | 1 Or 2 | • | • | ||
| Archive Room | 150 | 1 Or 2 | • | • | ||
| Active Archive Room | 300 | 1 Or 2 | • | • | ||
| Educational Institutions : | ||||||
| Class Room | 250 | 1 Or 2 | • | • | ||
| Library | 300 | 1 Or 2 | • | • | ||
| Lab | 500 | 1 | • | • | ||
| Drawing Room | 750 | 1 | • | • | ||
| Canteen | 200 | 1 | • | • | ||
| Hotel & Restaurant : | ||||||
| Lobby & Corridor | 100 | 1 | • | • | ||
| Multipurpose Room | 200 | 1 | • | • | ||
| Dinning Room | 250 | 1 | • | • | ||
| Cafeteria | 200 | 1 | • | • | ||
| Bedroom | 150 | 1 Or 2 | • | |||
| Kitchen | 300 | 1 | • | • | ||
Example: Workspace of length x width = 3 x 4 meters, so the area is 12 M². What are the appropriate lamp requirements?
From the table above, the lighting level that is suitable for the work space is between 120 ~ 250lux. We take the middle value of 185 lux. This value is still bright enough for sufficient lighting needs for work or reading activities.
From the previous explanation:
Lux = Lumen per square meter, or
Lux = Total Lumen / Area of Space
Then:
Total Lumen = Lux x Area of Space
= 185 lux x (3x4 m)
= 185 lux x 12 m²
= 2,220 lumen
Next determine what type of lamp to use:
- Incandescent (Bulb)
- Fluorescent (Neon)
- (LED) Light Emitting Diode
*Note: The installed lamp is a standard model of housing with ordinary light fittings, not a downlight model. Because the calculation will be different.
After knowing the total lumens, how many lights do we need?
For example, if you use Hannochs Premier 7W LED = 680 Lumen, the number of lights needed:
= 2,220 lumen: 680 lumen
= 3.2, can be rounded up to 3 lights
Tips and Tricks
The results of the above calculation with 3 lights are actually not an absolute result.
We must also consider the cost factor for the installation of these 3 lights.
There are several choices that can be a solution for you.
A. Use a Lights with Larger Watts
Lights that have a larger Watt will have a greater Lumen value.
For example, use Hannochs Premier 16W = 1600 lumen LED lights
By calculation:
Lux = Lumen / Room Area, Lux is produced
= 1600 lumens: 12 m² = 133,3Lux
The 133 Lux value is still included in the recommendation for lighting levels for the workspace from the table above, which is between 120-250 Lux.
So it's enough with just one light point.
So what needs to be considered is not how much the light points are, but how much lux values still meet the requirements.
B. Use a Reading Lamp or Table Lamp
The choice of using a lamp with a large Watt can cause a waste of electricity.
Because maybe the lights in the room must be lit longer, while working time is only briefly.
For that, a solution using a desk lamp or reading lamp will be one of the energy-saving solutions.