As the days shorten and we turn the clocks back, it may be a great time to think about installing or improving lights in some of our indoor spaces. Maybe you could use a bit more light to see the drill size marking in the workshop. Or, perhaps, you’d like to be able to sort carrots better with a bit more visibility. Or, maybe that corner where you perch with the laptop and order forms could use some task lighting.

Regardless of the need, there are a few key things to consider when thinking about lights.

Natural Light: Healthy and Free!

The first thing to consider is whether you can provide some of your lighting needs naturally, using daylight. If you have a building already, perhaps consider moving the work area near an existing window. You could add windows, of course. Or, if you are planning a new construction project, consider the layout of the space and window placement to capitalize on natural lighting. Another option is clear or opaque roofing materials such as rigid, polycarbonate greenhouse panels or corrugated plastic roofing. Consider the need for shading in the summer and make use of passive solar design principles such as window height and roof overhangs to achieve this. Northern light, being diffuse, is generally preferred as work light and will naturally prevent overheating from direct sunlight.

Sometimes you don’t even need to add lights! Windows or transparent roofing panels can transform a space with natural lighting requiring no additional energy input during the daylight hours.

Ratings – Lumens and Color Temperature

If you need to install lights, look for a light fixture (or bulb, or combination) with a detailed specification sheet or label.  It should note both “lumens” and “color temperature” (in K). Lumens is a measure of the output intensity (how much light is emitted from the fixture). Color temperature is a measure of the visual quality of that light (how yellow or white or blue it is).

  • Lumens = how much light
  • Color Temperature = the color of the light

Sometimes a light fixture combines the fixture and a lamp in one assembly. Sometimes different lamps or bulbs can be swapped into the same fixture. The lumens and color temperature ratings are the result of the combination. A different bulb in the same fixture can result in different lumens output and a different color temperature.

This wash/pack area makes ample use of natural light with careful placement of windows and supplements with overhead lights.

How Many Lights Do I Need?

The number of lights needed depends on the activity being illuminated, the specific light fixture’s lumens, and the area or square footage of the space. Here are some guidelines.

Activity or Uselumens per ft2 of area
Walkways or hallways10
Mechanical workshops or Office areas70
Detailed mechanical work areas (work benches, near shop tools)90
Fine mechanical work with small components, electronics work (fine adjustments, small parts, hard to reach locations, packing areas)180
Visual inspection of low contrast items, small items, or for long periods of time (sorting produce, working with labels, reading lists, desk work)450
based on https://www.engineeringtoolbox.com/light-level-rooms-d_708.html

Example – General Lighting for a Multi-use Open Space

Let’s assume you have a 20 ft x 20 ft pole barn that has recently been closed in against the weather and you want to light it for general use. That’s 400 square feet (20 ft x 20 ft). This area is going to be used for general tasks that don’t involve a lot of close, detailed work. So we need about 70 lumens per square foot from the table above, or a total of 28,000 lumens (70 lumens / ft2 x 400 ft2).

This works out to about 5 of these high output 4ft LED fixtures (5200 lumens @ 4,000 K color) or 5 of these fluorescent fixtures with these bulbs (2 bulbs per fixture @ 2,850 per bulb = 5,700 lumens per fixture).

General lighting in a barn. This is probably enough to see what’s in the space and find your way around, but it may be a bit dim for any detailed work, especially on the edge of the room.

Example – Task Lighting for a Workbench

Let’s assume you have a 3 ft x 10 ft workbench or vegetable sorting belt where you do pretty detailed work for long periods of time. That works out to 30 square feet (30 ft x 10 ft). The amount of light we need, based on the table above is 450 lumens per square foot. So we need a total of 13,500 lumens (350 lumens / ft2 x 30 ft2).

This works out to about 2 of these high output 4 ft LED fixtures (7000 lumens @ 4000 K color).

This workbench at the Extension Ag Engineering Lab is an example of task lighting. The work done here is detailed and visual and needs lots of good light. In this case, we were looking at changes in garlic during a curing trial. The light fixture shown is the one noted in the example above, the table is about 3 ft x 4 ft, half of the area in the example.

What Light Color Temperature is Best?

Light color temperature can be a very subjective thing. It is measured in K, or “Kelvin”. Lower K values around 1000-3000 are generally perceived as more yellow or orange. Higher K values of 5000-9000 are generally perceived as more blue or white. “Natural daylight” at midday on a clear day is somewhere around 6500 K, but most people find this too white or even blue when it comes from an indoor light. This can be good for short-term, high visibility needs like inspecting something or making a fine adjustment. But, most people like lower light color temperatures for prolonged tasks like reading or for illuminating the space around a computer workstation which already has a display with a fairly high light color temperature.

You can get a better sense for what each color temperature on the Kelvin scale actually looks like in this post on Shutterstock.

Water and Shatter-proof Fixtures

It may also be important to consider covers and water-proof / shatter-proof fixtures over any places where crops and food are being handled or where you plan to be hosing down regularly. Shatter-proof fixtures help prevent mechanical adulteration or contamination of food. Waterproof and/or high humidity fixtures may be important in fruit and vegetable washing, packing, and storage areas where regular cleaning and sanitizing may be needed.

Shatter-proof, water-resistant LED fixtures help brighten up this walk-in cooler so the growers can find what they’re after quickly and can keep the space clean.
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