Workshop Garage lighting question, looking at T5HO fixtures

[BrianGT]

Workshop Garage lighting question, looking at fixtures

First post, but have been lurking for years.

I engineered a second garage into my driveway during my new house build last year, and am looking to finish it out the second garage as a workshop. It is underneath my driveway, with 12" thick 12' tall concrete walls, and 10' steel beams supporting driveway slab above. It was a bonus feature of engineering a decent driveway turn-around for a driveway on a sloped lot, and avoiding having 12' of fill under my driveway.

Anyway, I am considering using Lithonia 8' T5 High Output fixtures from Home Depot (TZR 2 54T5HO MVOLT 1/4 GEB10PS):
Home Depot fixture link
with 5000k bulbs (specs showing 4800 lumens per bulb)

Room is 272 sqf (~25 m^2), with the 16 x 4800 lumen bulbs, will this be enough light output for a workshop? From what I can find on the web, with an approximated coefficient of utilization of .54 and a light loss factor of 0.8 (from other examples I can find for t5 HO fixtures/bulbs), this should give about 1327 lux. I am planning on re-wiring the ballasts with two switches to allow for running half the bulbs at a time to cut the light output in half.

Based on this example calculation site, I am approximating this:
I = 16 (4800 lumens) (0.54) (0.80) / (25 m2) = 1327 lux
(or 663 lux with half of the lights on)

Questions:
- This is my first attempt at calculating workshop illuminance, basing the calcs from other threads and web searches. Are these calcs reasonable? Would a reflector on the fixture improve the utilization coefficient?
- Is this a reasonable level of lux for a workshop (with all the wall concrete with the exception of the 8'x7' garage door, no natural light penetrates)
- Cost wise, the T8 fixtures are not much cheaper, and with the additional fixtures/bulbs to make the same lux, it seems like a wash, with the lesser fixtures being cleaner. Any advantage to having more T8 fixtures, vs the T5 HO fixtures?
- color temp wise, I was looking at going with 5000K, as 6500K seems too blue. Any cons of 5000k vs 4100k?
- for affixing the lights, I am looking at using 1/4" beam clamps to secure rails perpendicular the the beams for securing the lighting fixtures to.

Thanks,

-Brian

 

[cybrdyke]

BrianGT, it looks like you're on the right track. I dont see any mention of the material of your ceiling and that can make a difference. The strip fixture you linked to has uplight that would normally bounce off the ceiling and walls to add additional light. If you have a white ceiling these would be good. If you have another kind of ceiling, like an open ceiling or dark material, then you might consider getting an industrial fixture, which is the same as the one you linked but with a gull wing reflector attached. This will throw any uplight back down onto the surfaces below. Your block walls aren't very reflective either, so another point to have reflectors. Normally T5HO fixtures are used above 12', as they are very bright and set too low, they can be glarey. That's just a rule of thumb. Lower than that, I'd recommend the T8's. Color of lamps is completely subjective. Whatever YOU like best. They get bluer as the number gets higher. 6500 are really blue. 5000 are popular on this forum for workshops. 4100 is used in offices, schools, retail, etc. Did you look at anything LED?
Hope this helps.
CD

 

[BrianGT]

I appreciate the feedback. I didn't consider the glare concerns from the more intense light source, vs a spread of the a larger quantity of T8 bulbs.

I plan on painting the walls and beams white. There is galvanized steel for the roof that provided the containment for the concrete slab above, see below for pic during construction last year. All walls are poured concrete, and should take the white nice. I was looking to keep the roof as is, unless white would make a significant difference.

I did the entire house with LED lighting, but didn't look at options for the workshop, as the light output didn't seem to be high enough.

Considering the possible glare of the t5ho bulbs, it looks like going from 16 t5ho to 24 t8 should provide close to the same output. Using something like this, with an integrated reflector could help as well. Data from that fixture

Attached a pdf of the same layout with the T8 fixtures used instead. Cost will is just about the same with either BOM, ignoring the extra work hanging 12 x 2-bulb enclosures vs 4 x 4-bulb enclosures.

For the T8 bulbs, is there an optimal height, possible lowering them below 11ft?

Thanks,

--
Brian

 

[Norcal]

I would think the T5 HO would be too bright, they are intended for taller heights then run of the mill shops & garages. Lamps are a lot more expensive then the more common T8's also.

 

[BrianGT]

Planning on going with T8 lights instead. I appreciate the feedback. I am looking to design for 7 overhead lights, and 3 task lights on the bench, and designing to allow for 6 additional overhead lights, should more light be desired.

Played with conduit routing, and threw together a quick animation:

 

[RedDirtRoad]

Brian,
I have have the same T5HO fixtures in my garage and I bought them from Home Depot too.
My garage is 24x24. I have (4) 4ft fixtures along the front of the garage wired to (1) switch and (4) 4ft fixtures running along the back wall wired to another switch.
I also have (2) 8ft fixrures dead center wired to a 3rd switch. The fixtures in the middle of the garage I use as I enter the garage. The 2 sets of 4ft fixtures i use as needed.
My garage is bright with no shadows at all
here is a photo.