Hello all, my name is Jason and I am a fairly new member here. I have been reading over all the post and getting some really good ideas for my garage. I like the looks of can lighting but do not know how to calculate how many for a garage that is 21x19 with 12 foot ceilings.
The problem with (at least most) "can" type fixtures is that their light output is VERY directional. This in turn almost inevitably leads to woefully uneven lighting, with lots of alternating "hot spots" and shadow areas. Look at the photo posted by "ddawg16" for a perfect example of this phenomenon: I count at least four different "hot/cold" zones just within the small area area of that workbench/cabinet setup.
If someone can steer me in the right direction that would be awesome.
Cans are great when you want "dramatic" lighting (cf. that photo, again); but they are generally not very practical in a garage/shop, except perhaps as dedicated task lighting over stationary machines and/or work tables. For your general lighting, you would surely be far better served by something like:
http://www.homedepot.com/p/Lithonia-Lighting-2-Light-Utility-Light-3348-2L32W-WRAP/100654395
http://www.homedepot.com/p/Lithonia...hite-Fluorescent-Light-Fixture-3324/202192968
every fixture has a data sheet that you can get from the manufacturer. this sheet will show what the light pattern is at a given elevation. get the sheet for the fixture and trim you want and then space them accordingly
Just to further elaborate on this...
If you go this route, the critical point on those graphs will be where the light output has diminished by about 50%, vis-a-vis the on-axis value. Find that "half intensity" angle, then apply some basic geometry to determine what the horizontal distance from the lamp that angle corresponds to AT THE WORKING HEIGHT (which, given the OP's 12-foot ceiling, would be no more than about 8-9 feet). Your on-center fixture spacing should be no more than double that figure.
Nice thing about cans is that you can play around with different CFL or LED wattage values.
Well, you CAN; but that would only influence the overall maximum brightness levels. It would do absolutely nothing to improve the EVENNESS of the illumination, which is strictly a matter of the fixture/lens/bulb design vs. the fixture-fixture spacing.
I have 16 cans in my garage...20x25.....I think it's about right...I'm using 23w CFL's....
In addition to the "spottiness" issue noted above, that strikes me as a marginally inadequate amount of light to start with, even if it were distributed completely evenly. At about 1,600 lumens for a typical 23W CFL, you're looking at an AVERAGE source brightness of only 51.2 lumen/ft.^2. By the time you're down at working height, it would be considerably less than that. But the big issue is still the uneven distribution: While you might have 75 (or more) lumen/ft.^2 in the "hot spots", you will have correspondingly less than the average in the shadow areas.
