Shop Lighting

[Micheal Roth]

What is the difference between regular T-8 flourescent lighting and the high out put version. Is it really that much different to justify the added cost.

[Leo Graywacz]

Looks like they have about 30% more output per tube. So you would need 30% less lighting. So for every 3 fixtures you would have to buy you only need 2 HO fixtures. Figure out the pricing and you will know if it is worth it or not.

You will be getting the approx same amount of lighting per watt of power. Having more normal output fixtures will make the lighting more even. But you will need more wiring, outlets, possibly circuits. You also need to put those prices in your equation when figuring out is it worth it.

[Rich Neighbarger]

T-8 bulbs are smaller than standard T12 bulbs. You can look at it as fewer fixtures to equal the same light output, or the ability to install more fixtures for even more light per sqft.

[Bill Brady]

The Kelvin temperature measurement is higher on a high output lamp. The highoutput will be a whiter light. Depending on your shop size and ceiling height you may not get any benefit. A standard T-8 in a cool white will probably be good.

[Leo Graywacz]

I have been gravitating towards the higher Kelvin temperature bulbs, color corrected. I started out with cool white and switched to 4100K. Then I put some fixtures in that had T5 bulbs with 5900K temps. Big difference in color reliability. Very close to sunlight. So now the lowest temp bulb I have in the shop is 5000K and they seem a bit red to me compared to the full spectrum 5900K bulbs.

[Rob Hermann]

Also, although more expensive up front, if you do go with VHO bulbs you can get an electronic ballast to drive them. The electronic ballast use about 30% less electric than a magnetic one. Just something to consider.

[Micheal Roth]

I'm currently in the process of building a 24x36 man cave with room in attic trusses to give me an additional 12x36 room upstairs. The ceiling height will be 9' with 1/2" drywall on the ceilings and walls. I will also be painting both ceiling and walls with white semigloss paint.

[Leo Graywacz]

And what kind of lights are you putting in there?

[Warren Johnson]

Michael
I looking at the adding some T-8 electronic cold weather lights also. I've bee advised it is better to have the ceiling painted a flat white for better light distribution; rather than a semi gloss or gloss finish. Maybe someone will weigh in on this.

[Jack Lindsey]

As Leo and Rich correctly state, high output lamps produce more lumens per lamp so fewer lamps will be required to achieve a specified lighting level. This may or may not be a good thing based on a couple of important considerations. First, do you want a fairly uniform distribution of light in your shop? Since tasks can be expected to move to different locations in the building most people would answer “yes”. This means fixtures must be located close enough together so that their distribution of light overlaps to avoid dark spots between fixtures.

The maximum spacing between fixtures to maintain uniformity at acceptable levels is found by multiplying the fixtures spacing criteria by the mounting height above the workplane. The spacing criteria are obtained from the fixture manufacturers photometric test report and the mounting height above the workplane is simply the vertical distance from the workbench to the fixture. For fixtures mounted directly to the ceiling use the distance from the bench to the ceiling. For example, if the bench is 2 ½ feet high and the ceiling is 10’, the distance is 10 – 2 ½ = 7 ½ feet. Spacing criteria are published for both spacing parallel to the fixtures and perpendicular. Typical values for strip fixtures are 1.3 parallel and 1.6 perpendicular. This means that for a fixture mounted 7 ½ feet above the workbench the spacing between fixtures in the end to end direction should not exceed 1.3 x 7.5 = 9.75 feet, and the side to side spacing should not exceed 1.6 x 7.5 = 12 feet. You will need to determine how many fixtures are needed for the lamp you want to use, determine the layout, and then see if the spacing meets the guidelines. If the spacing exceeds the guidelines you need more fixtures, possibly using lower output lamps.

Another consideration with strip or industrial type fixtures is direct glare. High output lamps produce more light per unit of surface area so they are visually brighter and may be objectionable when used on low ceilings and in very large rooms. Direct glare potential can be evaluated by obtaining a “Visual Comfort Probability” table from the fixture manufacturer. This is probably going to be difficult unless you are a professional lighting designer. My personal thoughts are to stay with standard output T-8’s under 10 feet or standard output T-12’s under 8’ to avoid direct glare problems, but that’s just my opinion.

Regarding the color temperature (Kelvin rating), color temperature is color temperature, and for fluorescent lamps it is a function of the phosphors used in the lamp. The fact that a lamp is standard or high output has nothing to do with it. Color temperature simply describes the visual warmth or coolness of a light source. For example, imagine that you place an iron ball in a fire and heat it up until it is a dull red. It’s early morning and when you take the ball out of the fire you observe that the color of the ball is the same as the red eastern sky just before the sun peeks over the horizon. If you measured the temperature of the ball you could than accurately describe the color of the sunrise by citing the temperature of the ball. We don’t use the F or C temp scales, though, we use the Kelvin scale. This is simply a different scale. For comparison, water freezes at 32 degrees F, 0 degrees C, or 273 Kelvins. Note that the units of the Kelvin scale are Kelvins, not degrees.

Back to the example – the color temp of the early morning sky ids about 800 Kelvins. For further comparison, incandescent lamps are in the mid 2000 K to 3100 K range. Warm white fluorescent is 3000K, cool white is 4100 K, etc. The higher the color temperature the more blue and less red. Lower K rated lamps are thus visually warmer.

A word of warning: don’t judge the color of a lamp by color temperature alone. There is another metric, color rendering index, which must also be considered. I’m not going into a discussion of CRI unless someone is interested.

And Warren, to answer your question, a flat painted surface provides better diffusion of the light so you will have a more uniform distribution of light in your shop. Also, highly shiny surfaces can produce objectionable reflected glare from bright lamps.

[Warren Johnson]

Jack,

Thanks for the answer about the paint. I believe it is your article in the Small Shops book from FWW I just finished reading and I am now laying out where my lights will be mounted. I have a very small portion of the garage that I can use for a work area, so I may have light hanging in 2 directions.

I plan to repaint the ceiling to a flat white finish.

Warren

[Eric Gustafson]

A word of warning: don’t judge the color of a lamp by color temperature alone. There is another metric, color rendering index, which must also be considered. I’m not going into a discussion of CRI unless someone is interested.

I was searching for posts on fluorescent lights and found yours. You did such a great job on color temp, can you explain CRI, too?

[Mike Cruz]

I put the T8 6' long 2 bulb versions from HD in my shop. The shop is 24 x 30. Each rafter has 2 fixtures along its 24' span. Rafters are 4' apart. There are 7 exposed rafters (9 total, one on each Gable end). So that would make 14 lights. That is in only in theory. Because of a finishing room and wood rack that combined take up 1/4 of the floor plan, I ended up with 11 lights.

In the section that is 24 x 15 (approx) there are 4 exposed rafters with 2 fixtures on each rafter along the 24' span. This accounts for 8 of the fixtures. I have these 8 on 2 seperate circuits (alternating rafters). So I can light up that entire area with either one of those two circuits (4 lights on 2 rafters that are 8 feet apart) or with both circuits (8 lights on 4 rafters that are all 4 feet apart).

In the section that is 12 x 15 (approx) there are 3 exposed rafters with 1 fixture on each rafter along the 12' span. This accounts for 3 of the fixtures. I have these 3 on 1 circuit.

Lights up the shop very well. Hope that wasn't as confusing as it may have sounded.