What is a Foot Candle?
A great place to start is with the definition. For those of you who may not be familiar with them, a foot-candle is a measurement of light intensity. One foot-candle is defined as enough light to saturate a one-foot square with one lumen of light.
If that sounds vaguely like the definition of a lumen, you aren’t wrong. Both lumens and foot-candles are measurements of light intensity.
While lumens measures the amount of light created by a lighting fixture, foot-candles is a measurement of the amount of light that reaches a surface area.
In accordance with other factors, foot candles allow electricians and facility managers to carefully and thoughtfully develop an effective lighting plan.
After all, it doesn’t matter how much light a bulb emits if none of that light reaches the desired surface area.
Below are base foot-candle measurements for the named light conditions:
Unobstructed sunlight: 10,000 foot candles (fc)
Overcast sunlight: 100 fc
Visually intensive workspace: 200 fc
Retail Store environment: 5 fc
Residential space (living): 5-40 fc
Residential space (working): 70-90 fc
If you want to just leave this to experts, we can’t blame you. We offer peace of mind with free photometric lighting plans for our commercial and industrial lighting customers, so that you can feel confident in your lighting layout.
Why Are Foot-Candles Important?
Foot candles are an extremely important part of designing an effective lighting setup. They are the only way to tell if an area is actually receiving the intended light levels.
And, although this is important in any type of business, it’s especially important for commercial and industrial facilities to have appropriate lighting levels for both employee safety and efficiency.
It’s so important, in fact, that OSHA has specific foot candle requirements for certain spaces and industries.
OSHA, or Occupational Safety and Health Administration , was created to protect workers by ensuring that working conditions were safe and as risk-free as possible.
As a part of their safety initiative, OSHA developed standards to make sure that all commercial and industrial workplaces have lighting that is adequate and effective, without having a glare or being excessively bright.
Glare and excessive lighting, which can cause headaches and eyestrain to individuals’ overtime. Read more about OSHA guidelines from the United States Department of Labor.
First aid locations, general office spaces, and hospital infirmaries: 30 foot candles
Factories: 10 foot-candles
Construction sites: 5 foot-candles
Warehouse spaces, covered walkways, interior corridors, exit locations: 5 foot candles
General under ground areas of work – mining and tunnels: 5 foot candles
Areas of Concrete placement, waste location areas, loading docks, storage areas, field maintenance locations, refueling locations and excavation sites: 3 foot candles
Additional Foot Candle Recommendations
Offices, manufacturing facilities, and workrooms require much larger foot-candle measurements than the average space. This helps keep employees safe and productive.
However, there are spaces in offices and industrial facilities, like hallways and lobbies that don’t need quite as much light. In areas like these, where people aren’t doing intensive work, bright lights would be overwhelming.
The lighting should be bright enough to show hazards, but not so bright they feel uncomfortable in the environment. Its about striking the right balance. Using lower light levels in these areas is also a great way to cut costs.
Museums are unique in that they require high foot candles to show off the art, but like to keep lighting soft in the surrounding areas.
Foot candle measurements are especially important here as lights can sometimes damage precious artwork. So knowing where light won’t reach is often just as important as knowing where it does reach.
Security. Any business with security concerns should take extra precautions to ensure that the foot candles around all entrances and exits are bright enough for cameras to pick up everything they need.
Understanding Lighting Plans
A Photometric Study, or Lighting Plan, is a report detailing the light levels and light distribution for a location, either indoors or outdoors. It’s done by software that’s was specifically created to do so.
Lighting Plans allow you to simulate a space, add lighting fixtures, and set mounting heights and fixture locations within the software model.
The software calculates light levels and how balanced the light is and produces a report showing average, max, and min foot candles.
For this discussion, the numbers we discuss are the average recommended foot candles. Just as important are the max/min ratio the study calculates. The higher this number is, the more spotty the lighting.
So it’s one thing to hit the recommended average. It’s another to design a lighting solution with even light distribution. A lighting plan study will provide you with this information.
Workshop Lighting Plan
What is a lumen? A lumen is a measurement of light created by one bulb, lamp or fixture. We use lumens to indicate the brightness of a bulb or fixture – how much light it produces. Lumens is a far more accurate representation of the light’s capacity than watts used to make light.
Watts measure the amount of energy used to produce light. Because LEDs were designed to be energy efficient, compared to traditional light sources like fluorescent bulbs and metal halide, they use much, much less energy.
When doing a lighting plan, we add lights to the report at their specific locations. We then use the lights’ lumens to determine how many foot candles are present.
Choosing the right optic along with the lumens aids in getting an even distribution, and helps you reach the desired foot candle levels.
Understanding Light Efficiency
Even amongst LEDs, not all bulbs are created equal. Though they are all more efficient than options like fluorescents and metal halide options, not every LED is equally efficient.
This is another reason why it’s important to pay attention to the lumens of an LED light instead of the watts. In many cases, a higher quality LED with lower wattage can produce a brighter light than one with a higher wattage.
Let’s explain this showing 2 examples.
One fixture is a light at 130 lumens per watt. The other is a light at 180 lumens per watt.
To produce 20,000 lumens, the first light needs 153.84 watts. The second light only needs 111.11 watts. That’s a difference of 42.73 watts. This is what saves you money on your lighting bill.
Both lighting products above create the same amount of light, or lumens.
Efficacy, or light efficiency, is another important thing to factor into a light purchase. A more efficient light may cost more at the time of purchase, but over the life of the product, your utility bill will be lower.
And the amount you save with a lower utility bill will far exceed any additional purchase cost. If you want to learn more about LED lumens and all that goes into them, we’ve summed it up nicely in this post.
Recommended Light Levels
Lighting systems are not equal. What may be ideal for one location may be unsuitable for another.
For instance, a big box store does not need the same amount of light as a packaging warehouse. Even if two facilities have the same square feet, the activities carried out may be different.
The work performed in a building usually dictates the fixtures required for illumination. This is why a “one size fits all” approach is never recommended when choosing lighting.
OSHA requires workplace lighting measurements in foot candles. In this article, we’ll give foot candle recommendations for different types of environments.
Recommended Foot Candles for Offices
|Open Cubicle Space||30 fc|
|Reception Areas||10 fc|
|Conference Rooms||30 fc|
|Video Conferences||50 fc|
Recommended Foot Candles for Exhibition Halls and Venues
|Washrooms and Restrooms||5 fc|
Recommended Foot Candles for Shopping Malls – Retail – Grocery
|Main Concourse Areas||30 fc|
|Service Areas||30 fc|
|General Retail||50 fc|
|Stock Areas||30 fc|
|Food Supermarkets||50 fc|
Recommended Foot Candles for Food Services
|Food Courts||30 fc|
|Dining Areas||10 fc|
Recommended Foot Candles for Hospitals – Medical Facilities
|Patient Waiting Areas||10 fc|
|Nurse Stations||30 fc|
|Lobby Areas||5 fc|
|Medical Record Areas||50 fc|
|Stair Areas||10 fc|
Recommended Foot Candles for Hotels
|Guest Rooms||10 fc|
|Hallways – Stair Areas||5 fc|
Recommended Foot Candles for Schools
|College Lecture Halls||50-100 fc|
Recommended Foot Candles for Factories and Warehouse Facilities
|Coarse Material Processing||10 fc|
|Medium Material Processing||30 fc|
|Fine Material Processing||50 fc|
|Extra Fine Material Processing||50-100 fc|
|Wrapping, Packaging and Labeling||30 fc|
|Picking Stock||30 fc|
|Simple Assembly||30 fc|
|Difficult Assembly||100 fc|
|Complicated Assembly||100-300 fc|
|Warehousing – Inactive Area||5 fc|
|Warehousing – Active – Large Items||10 fc|
|Warehousing – Active – Small Items||30 fc|
|Shipping and Receiving Area||30 fc|
|Maintenance and Shop Areas||50 fc|
Recommended Foot Candles for Outdoors and Exterior Lighting
|Parking Garage – Basic||1 fc|
|Parking Garage – Ramps||1-2 fc|
|Parking Lots||2-5 fc|