How Much Light is Needed?

Before undertaking any lighting retrofit project or designing a lighting system for a new facility, determine appropriate and adequate levels of illumination for required activities both inside and outside the facility. Take a close look at each area to see what the lighting needs really are. Ask people how they feel about the lighting: is there too much or too little light, is there glare?

If you want to check people's impressions and your own, you can measure the amount of light with a light meter. Your lighting supplier can probably lend you one. You can then compare your present lighting levels to nationally accepted recommendations. When measuring levels with a meter, be sure to take into account whatever contribution daylight is making. You need adequate lighting on overcast days and at night. In many cases, you will find present lighting levels are excessive and need adjustment, which are usually achieved through delamping or conversion to a different lighting system. The Illuminating Engineering Society (IES) recommendations for lighting levels for various activities are shown in this table.