Okay I need some help on my shop lighting. I have a 24x26 shop with only an 8’ ceiling, I know that’s low but when it was built it was supposed to be for storage only but now it’s become my shop.
Such is life. The 8-foot ceiling is not ideal; but it's not a disaster either, as long as you work WITH it, instead of against it. The main implication of that is, you need to keep the fixture-fixture spacing as close as reasonably feasible; which in turn means you do NOT want ultra-bright fixtures/tubes (standard F32T8s will do just fine). And choosing fixtures which provide some degree of impact protection (as opposed to open-tube "strip" fixtures) would be a good idea.
The 24x26 is from outside to outside measurements, it is a wood framed structure with 2x4 exterior walls. The lighting plan is a combination of 8’ and 4’ t-8 strips with the 8’ having 4 bulbs and 2 for the 4’
As others have mentioned, I'd go with all four-foot fixtures, with MAYBE a few matching two-footers thrown in as needed to fill out runs, etc.
and each square represents 1’. The garage door opening is 14’ and faces south.
Thank you for providing a real scale and directional reference in your sketch. You'd be surprised how often that gets overlooked, and how much blind guesswork that leads to when it's missing.
The 3 rows going from east to west concern me cause the center row I’m having to offset to one side or the other of garage door opener and attic access which in turn does not evenly space the fixtures.
The offsets you're showing are too trivial to worry about, at least in terms of lighting effectiveness. If you're deep enough into OCD to stare up at your ceiling and worry that things aren't EXACTLY symmetrical... Well, then this is probably not the best place to get help with that.
So here are some of my concerns.
1. Will this be enough lighting?
28 tubes @ 2,800 lumens/tube = 78,400 total initial source lumens. Over ~624 ft.^2, that averages out to about 125 lumens/ft.^2 -- maybe a
little high, but certainly not outrageous as long as you set up the switching correctly.
2. Is three rows running east and west enough?
Per your drawing, those rows are running North/South. But beyond that...
It depends in part on exactly how you envision using the space. Were it my garage, I'd probably put an additional row running East/West near the back, to provide illumination for whatever is stored on/near that wall, and to throw some light into open engine compartments. You're showing your workbench area along the East wall, which implies some additional task lighting there; so the general lighting in that area probably doesn't need to be quite as intense, but it won't hurt anything to leave it as-is.
3. Should I offset the center row to the east or west of the garage door opener and attic access?
Doesn't really matter. At least the rear-most one is going to have to stay more-or-less where it is anyway, simply because of the attic-access hole.
4. Should I add another row from east to west?
See above.
5. Are the fixtures going from east to west spaced too far?
As a practical matter, there's no really GOOD way to get them appreciably closer. So... No.
If anything, I
might move the outside runs a foot or so closer to the walls, to provide more of a horizontal offset between them and the vehicle(s) parked in those spaces, thus better illuminating the lower portions of those vehicles. But you don't have a lot of wiggle room here, as you also don't want them too close to the walls (1-1/2 to 2 feet, minimum).
6. Should I try to rearrange the fixtures from north and south to east and west
Not sure what you're asking here. But basically, you want the main runs to be oriented more-or-less the way you have them, so as to put the light AROUND the cars (i.e., where you'll actually be working). The additional East/West run mentioned above will also aid in this pursuit.
7. Should I use all 8’ or 4’ fixtures only or is a combination of both okay?
Stick with the shorter fixtures. This provides more flexibility in terms of both placement and switching. In a space that size, "Zoning" is essentially useless; but granular control of overall brightness levels will still be valuable. To give you an example of what I'm talking about... In my slightly smaller (approx. 20'x20') garage, I'm planning on three main "runs" of fixtures in a big "U" shape (i.e., down both sides and across the back). Each of those "runs" will consist of four of these:
http://www.homedepot.com/p/Lithonia-Lighting-2-Light-Utility-Light-3348-2L32W-WRAP/100654395
with one of these:
http://www.homedepot.com/p/Lithonia...hite-Fluorescent-Light-Fixture-3324/202192968
in the middle of the string.
The center of the space will be filled with a third front/back "pseudo-run" of two or three more of the four-footers (the exact number will depend in part on whether I swap out the conventional chain-drive GDO for a torsion-spring model which can mount off to the side, out of the way; haven't really decided on that yet).
The three two-footers will be switched together as my "walk through" lighting. Two of the four-footers in each main run, along with at least one of those "center fill" four footers will be on another switch; and the rest of the lights will go on a third switch.
Point is, a very similar approach should work just as well for you. Given the somewhat larger space you have to work with, I'd probably skip the two-foot fixtures, and just use five four-footers in each of the main runs. But you can still take a near-identical approach to the layout & switching, with that corner-mounted heater being the only serious obstacle.
