Fellow Garage Journal Brethern,
After running electrical and hanging Sheetrock, my garage will be done. It is a stick built 28'X30' with 12' ceilings. I had my mind set on the T5 fixtures, 48"/4 bulb fixtures, I have all but wrote the check out for them. However, as of late, I have come across more than one thread on here that states T5 fixtures in a garage with 12' ceilings is not the most wise choice. I'm reading that more like a 14' minimum is needed. Is this accurate?
It depends.
As Charles pointed out, there are two general classes of T5 fluorescent tubes: "Standard" (F28T5) and "High Output" (F54T5HO). The former are basically comparable to standard F32T8 tubes in terms of both light output and power consumption, but a tad more efficient (i.e., slightly brigher, while using slightly less power; but in both cases, the differences are only marginal). Hence, they can be used in pretty much all of the same applications, with similar results.
The latter, however, can be problematic in low-ceiling applications; and the "High Bay fixture vs. Low Bay fixture" issue mentioned by Charles is only part of that problem. Fundamentally, it comes down to intensity vs. evenness of distribution. When designing the lighting scheme for any given workspace, you start by setting a target brightness at the work surface/height. For a "serious" garage, that is typically around 100 lumens/ft.^2. For your 28x30 space, and
presuming that the light is distributed perfectly evenly, that means a total light output of about 84,000 lumens at "working height" (somewhat more than that in terms of "source lumens"; but for purposes of this illustration, let's ignore that distinction in the interest of simplicity).
There are any number of possible ways to meet that target. For example, you could use 100 lamps, each capable of producing 840 lumens (such as, for example, these:
http://www.1000bulbs.com/product/64863/IN-270827.html). At the other extreme, you could use just four very bright lamps, each capable of providing 21,000 lumens (say, for example, these:
http://www.1000bulbs.com/product/53985/MH-02001.html). But neither of these is likely to be satisfactory. In the first case, it would mean a LOT of wiring (and at least in the case of the example above, the bulbs themselves are very inefficient). In the latter case, and given the relatively low ceiling height, the light would be FAR too unevenly distributed: The areas near those four lamps would be unbearably bright, while the areas further away would be horridly dim (particularly by comparison). Now,
IF the ceiling was MUCH higher, this would be less of a problem, because the light from each source would have more opportunity to spread out and diffuse throughout the space as it travels down from the ceiling to the working surface; but it would take perhaps 20-25 feet (maybe more) of installed height to get such intense light sources to spread out ENOUGH to be usable in that space (which, coincidentally, means you would lose still more efficiency due to the increased source-to-target distance).
While that is obviously an extreme example, fundamentally the same principles apply when choosing between F32T8 (or F28T5) tubes and F54T5HO tubes. As a general rule, presuming relatively low (less than perhaps 15 feet or so) mounting heights, the latter simply provide TOO MUCH light per fixture (especially if there are more than two tubes per fixture); and so lead to using too few fixtures to EVENLY cover the space, despite the "average" brightness meeting (or even exceeding) your target.
Like I said, I just stumbled across this contraindication for the T5's, is this a valid argument, do I need to look at T8 fixtures? As for what I'll be doing in my garage, that will consist mostly of wrenching on my muscle cars, rebuilding carbs, engines, etc. So the whole reason I was willing to invest in T5's was for the incredible light output needed for such tasks.
First, for such things as "rebuilding carbs", you should be relying on well-implemented task lighting directly over your workbench. The shop's GENERAL lighting does not really bear on this very much. Beyond that, the most important goal you have for your general lighting is to avoid dim areas and shadows (including shadows created by the vehicles themselves). So PLACEMENT of the light fixtures becomes the really critical issue; and (again, in general) twin-tube F32T8 fixtures give you the most flexibility in terms of placement, as well as being "dim enough" (yes, I know that is a counter-intuitive term; but think about it) to allow you to use enough of them to TRULY cover the work areas evenly.
T5 or T5HO?
T8s are great IMHO, but like anything they will be the "old school" and the T5s will be the new standard.
T8s will be around for a LOOOOOOONG time. No need to worry about that.
OP, I run T5HO 4' and 8' fixtures in my 9 - 10 ft ceiling and it works GREAT.
Here is a picture of my (junked up and messy) welding table as I was making a cord for something:
{image deleted}
No special camera tricks, hand held the camera at like 11PM at night without issue! Tons of light.
{image deleted}
With 12' you can't go wrong.
I appreciate that picture for reference. It looks as though the sun is shining in there man!
It is fundamentally
IMPOSSIBLE to meaningfully judge "brightness" from a photo posted here (or anywhere else online, for that matter). It's all about the camera's exposure settings; and in fact, it would indeed take some VERY "special camera tricks" (which would likely fail anyway) to even attempt to make such comparisons valid or meaningful.
