Following this procedure you should be able to successfully light a space to whatever requirements are set forth. This procedure can be easily adapted to suite the needs of most lighting requirements.

This procedure is broken down into five "Primary steps". Each "Primary step" may also be broken up into multiple smaller steps, which must be accomplished in order to complete the primary step.

Primary Steps

1. Read through the governing specifications or talk with the person capable of making the important decisions. Determine what level of illumination will be required to properly light each room or compartment.

1. Decide on which type of fixture you are going to use and ensure that there are no conflicts with any requirements that have been set forth within the project.
2. Determine the number of fixtures it will take to provide the specified illumination in the compartment or room using the LUMEN METHOD
3. Arrange the fixtures to provide uniform illumination throughout the compartment. Generally speaking the lighting should be spaced about the same distance apart as their mounting height above the flooring, decking or raised decking. COMMON ARRANGEMENT EXAMPLES
4. The last step is to check your work to ensure that the proper illumination will be achieved by your design. This checking process is accomplished by using the POINT-BY-POINT METHOD. If all illumination requirements are met then you are finished. If the Point-by-Point method shows that your design does not meet every requirement, you will then have to rearrange your lights, add or subtract a light or two or even switch to a different type of lighting fixture. After any changes in lighting position or type you will have to once again perform the Point-by-Point method.

LUMEN METHOD

The Lumen method of lighting design is used to calculate the number of fixtures required. This method takes into account not only the direct lighting, but also the light that is reflected from the ceiling or overhead, the walls or bulkheads and the deck or floor.

This method has seven steps, which need to be accomplished in order to determine the correct amount of fixtures you will need to meet your specific lighting requirements.

Steps for Lumen Method

1. The first step is to determine the Cavity Ratios. There are three Cavity Ratios that need to be determined.
1. Ceiling Cavity Ratio which is five times the height of the ceiling cavity times the sum of the compartment length and the compartment width all divided by the product of the compartment length and compartment width.
2. Room Cavity Ratio is five times the height of the room cavity times the sum of the compartment length and the compartment width all divided by the product of the compartment length and compartment width.
3. Floor Cavity Ratio is five times the height of the floor cavity times the sum of the compartment length and the compartment width all divided by the product of the compartment length and compartment width.
See the LUMEN METHOD WORKSHEET to determine these ratios.
2. The second step is to estimate the reflection factors for the ceiling, floor and walls. These values should be the minimum expected just prior to cleaning or repainting. These values will either be given to you or you may have to estimate them yourself in which case you can use this table as a guide.

COLOR	REFLECTION FACTOR
White, light tints of blue-green, cream, blue, buff, gray, or white pine wood finishes	.75
Medium blue-green, yellow, medium buff, gray, light wood finishes	.50
Dark gray, medium blue	.30
Dark blue, brown, dark green and dark wood finishes	.10

Feel free to estimate values higher or lower than those indicated in the table, just keep in mind that at the reflection factor approaches 1.0 the more reflective the surface is and as the factor approaches 0.0 the darker the surface is.
3. The third step is to determine the Cavity Reflectances. These refer to the effective reflectance of each cavity. Use the EFFECTIVE REFLECTANCES TABLES to determine the value of each.
4. Next you will need to determine the Coefficient of Utilization. The Coefficient of Utilization is used to account for the amount of light absorbed by walls and ceiling, and the light absorbed by the fixture itself. This is probably the hardest part of the lumen method since it requires tracking down the information from the company that makes the lighting fixture. Select the Coefficient of Utilization from the CU table provided by the manufacturer. In the advent that the table can not be obtained you may use the APPROXIMATE COEFFICIENTS OF UTILIZATION TABLE but, the manufacturers tables will be the most accurate.
5. The light loss factor now needs to be determined. The light loss factor accounts for the dimming of the light due to dust/ dirt on the light or just dimming due to the age of the light. The light loss factor ranges from Zero to One. One is no loss what-so-ever this is basically a new, relamping, or ideal situation. Zero is total darkness and you wouldn’t need to calculate this since it would just mean that the lights are out and its very dark and you would need a flashlight. I have listed some estimates below, each value is classified as clean, average, or dirty. Clean means that there is fresh air, free of dirt and dust, and the lights are either new or have just been cleaned. Average means the air is pretty clean, maybe a little cigarette smoke and you might only clean the fixtures when a light burns out and you have to replace it. Dirty means your in a pig sty filled with cigar smoke so thick that you can cut it with a knife.

 

Lamp and Fixture	Clean	Average	Dirty
Incandescent	.74	.69	.64
Quartz	.82	.76	.70
Mercury	.70	.65	.60
Metal Halide	.64	.59	.55
High Pressure Sodium	.77	.66	.66
Fluorescent	.71	.66	.61

6. Calculate the Lamp Lumens Required. This is accomplished by using the formula below or by filling in the LUMEN METHOD WORKSHEET ,

Total Lamp Lumens =

Footcandles X Area of Room (sq. ft.) / Coefficient of Utilization X Light Loss Factor.

7. Lastly you need to determine the total number of fixtures required by using the formula below or again by completing the information in the LUMEN METHOD WORKSHEET        ( Typical Lamp Lumens can be found by clicking here )

 

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