I am getting close to wiring my new shop. It roughly 30 x 40 with 9 foot ceilings. It a daylight basement but I have a minimum of windows. The shop ended up more below grade that I expected. My plan once we get it dried in to paint the walls white to lighten it up. Then install T8 fluorescent lighting. I am going to look at 8' and 4' fixtures and compare prices to see which is the better deal.
But my question is spacing and how many fixtures? I read somewhere to use single bulb fixtures spaced at 4 feet. But so far that is all I have found. Search the web a good bit tonight and found nothing. Anyone know of a good reference on this?
Kudzu < The man that always tells the truth never has to remember what he said
You have a couple of choices: An array of lights all over the room that are turned on simultaneously, or groups of fixtures that cover a particular area. Here are some suggestions:
Put a 2-bulb, 4-foot, 34/40-watt fixture over each workbench so you have strong lighting for fine work.
Put another over the table saw, bandsaw, jointer, belt/drum sander, and sanding table, as applicable.
For general lighting, based on 30 x 40 feet, about 6-9 fixtures in a 2 x 3 or 3 x 3 array would work nicely for general lighting.
There are no right or wrong answers. Lighting should be arranged to fit your "style" and interests. 4-foot, 2-light fixtures are cheaper to buy because they're a lot more common.
In the shop, work surfaces should receive 100 foot candles from the general lighting alone. A foot candle is one lumen per square foot. Additional task lighting is often desirable at individual work stations.
The 100 foot candles is what you want *after* losses. The major sources of loss are fixture inefficiency, lamp age, dust on lamps, and wall and ceiling reflectivity. Together, 8-10' ceilings, 3' work surfaces, and typical values for the aforementioned losses result in almost exactly a
50% reduction in the initial luminance of your lamps.
Fluorescent tubes typically supply 60-80 lumens per watt. A 40W tube, the most common and cost effective option, typically puts out about 3000 lumens when new. Accounting for the aforementioned losses, each tube will actually put about 1500 lumens on the work surface. Since you need 100 lumens per square foot, a tube will illuminate 15 square feet.
40 x 30 = 1200 sf; 1200 / 15 = 80 tubes, or 40 fixtures.
By the way, 40 watts per 15 square feet is 2.7 watts per square foot. Some lighting designers use 2 watts per square foot as a lower bound, which yields 20 square feet per 40W tube.
1200 / 20 = 60 tubes, or 30 fixtures.
For a rectangular area, you can run the rows parallel to the long edge or parallel to the short edge. Sometimes the choice is dictated by other design considerations, such as dust collection ducting or other obstructions. If not, be sure to consider both ways. You can often get more uniform lighting by running a higher number of shorter rows.
Incandescent and/or halogen lighting can be a good idea for areas where you finish pieces that will be used indoors. Fluorescent lighting has different color characteristics, and the color of a piece can "change," sometimes dramatically and unpleasantly, when brought from the shop to it's final destination.
My shop is about the same size as yours and I have dual lamp 8' T8's in my shop and have them spaced about 6 feet apart in all directions. My ceiling is 14 feet fwiw. SH
I don't know about a reference, but I did 2 shop rooms, one that turned out very well and one that isn't so great.
The room that turned out well is a daylight basement room about 19' x 38', with a ceiling slightly lower than yours (about 8' 9"), white walls, and the same lack of windows (glass panes in garage doors at one end, plus 2 small windows high in the side wall at the end away from the doors).
I used the dual bulb 8' high output fixtures that Lowes/HD carry, with
3 continuous rows running the long direction. The rows are spaced about 6 feet apart (3' from the sides) and suspended
4" off the ceiling (you have to do this with these fixtures, because the ballasts get hot). The rows have 3 8' fixtures each; I don't light the end of the room where the garage doors are because the door doesn't allow clearance and because we park cars there most of the time anyway. I switch them in 3 banks running perpendicular to the long rows, and the shop is organized such that I typically turn on only 1 or 2 banks at a time unless I'm just wandering back and forth over the length of the room.
These bulbs are 110 watts each, and it's nice and bright in there but I really don't think it is too much. For your shop, this scheme would translate to about 5 rows, with maybe 4 or 5 fixtures per row, depending on what you do at the ends of the room.
The room that turned out poorly is another room in the same basement where I used
4' T8's instead of the 8' HO fixtures, with roughly 4' between rows. The T8's are not not nearly bright enough for my taste. There are also 4' T12 versions of the HO fixtures available, but Lowes and HD don't carry them anymore. I plan to replace the 4' T8's with the 4' T12 HO's, one of these days. To be fair, this room is not painted white, and I think that makes a huge difference.
Actually, I prefer the "LGB" theory of lighting design as follows:
1) Walk the job site and scope out the area, either indoor or outdoor.
2) Make design recommendation such as put luminaires here, here, and here to the user while pointing towards the required area.
3) Ask question, "Are we done here?", If so, Let's Get a Beer.
Over the years, managed to sell a few $ worth of HID lighting equipment that way.
Only the names have been changed to protect the guilty >B/G>.
True, true -- but it's so much easier to cut the losses! (G)
Yeah, it's certainly not rocket science. Still, a lot of home shops are terribly under-illuminated. I know my first 15 years worth of shops were.
Truth is, I'm just a guy whose found over the years that it's often profitable to pay attention to the pros instead of paying them cash. When I needed some lighting design work done a few years ago, I spent a couple weeks studying the subject and did it myself. It was time well spent and has come in handy several times since then.
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