What is a foot-candle? How do you find out how many you need at your facility? As lighting professionals, foot-candles are our go to unit of measure to calculate light levels. The word foot candle dates back to when candles were the main light source available.
What is the difference between foot candles and Lux?
A foot candle is a measurement of light intensity and equals one lumen one square foot. A lumen is the amount of visible light given off by a light source. If you were to set a candle a foot away from a wall and draw a one foot square on the wall, the amount of light filling up the square equals one lumen. The more lumens, the brighter the space.
A foot candle is equal to about 10 lux. Lux measures luminous intensity just like a lumen, but is in the International System of Units (SI), which is the modern form of the metric system. A lux is equal to one lumen per square meter.
How do you read foot candles?
Our auditors will use a light meter to obtain an accurate foot candle measurement when they visit your facility. We use light meters at numerous points in your spaces to determine any specific dark spots and develop an average foot candle reading for each space. Additionally, for new light fixture installations or retrofits, photometric software can be used to calculate proper fixture spacing, lumen outputs, and use of proper lenses or distribution patterns.
How many foot candles do you need?
It depends on the location and what the space is used for. For perspective, generally you would see covered parking garage light levels in the 2-10 foot candle range, a gym 30-100 foot candles, and an office or chemical lab would have light levels in the 40 or more foot candle range.
The Illuminating Engineering Society of North America has a set of standard guidelines for particular applications when it comes to safety and adequate illumination levels. The guidelines are outlined in “The Lighting Handbook, 10th edition.” According to the handbook, for a cold storage or warehouse space it is suggested to maintain an average of 20 foot candles in the area. The same goes for an open warehouse or a warehouse with aisles. When it comes to office spaces, an open office or private office area should have a light level average of 40 foot candles. A classroom should also have 40. An automotive showroom or service area is ideally lit with a 50 maintained foot candle average.
How many foot candles are recommended for your location?
Most major corporations set lighting standards using the IES’ guidelines and if needed adjust those levels to suit their specific operations. Click on this link to download a reference guide for suggested light levels in even more facility types than mentioned in the previous examples: U.S. Energy Recovery Lighting Reference Guide.
Meeting recommended lighting levels through LED lighting
If you’re looking to meet recommended lighting levels in your facility the most cost effective way to do it is through LED lighting. Upgrading to LEDs is one of the best ways to reduce energy consumption and save money. On top of that, you’ll see an increase in productivity, quality, and safety.
If you have a specific question about suggested light levels within your business please contact us (800) 834-8737 and one of our team members would be glad to assist you.