how many 8' T8's for 30' x 40' ?

[stockcar36]

I'm currently having a 30' x 40' x 12' walls with a 4/12 pitch roof metal shop built. I'm going to wire it myself. I'm planning on installing 10, 8' 4-bulb T8's, five on each side running parallel to the 30' sides. I'll also have 4 skylight panels in the roof. Do ya'll think it'll be enough light for night use. I'll be working on my dirt track car and activities related to that, except I don't drink. Thanks!

 

[Charles (in GA)]

Open strip lights? Reflectors?

Charles

 

[stockcar36]

Open strips. Shop is insulated with white plastic faced insulation all over.

 

[bczygan]

20 Correction: 10 of the 8' fixtures with 4- 4' bulbs each
No skylight light at night.

30x40=1200SFx100FC/SF=120,000FC/2700FC/4' tube=44 Tubes/2=22 (2 Tube fixtures. Round down to 20 or even 18 to account for doors. Use T8 4' reflector fixtures mounted at 8'. Use 35Watt daylight bulbs. Put on 3 circuits.

 

[stockcar36]

My 8' fixtures will have 4 bulbs each, so I'll have 40, 4' bulbs. I also have 10' roll-up doors, so they won't be in the way. I'm planning on mounting the fixtures directly to the purlins but the middle one on each side will be on the center beam. So, I should be OK?

 

[NHBandit]

This is how I did my 30x40x12. I also went with scissor trusses to give me even more height above the lift. No problems with not having enough light. I wired them so I have 2 switches. 1 for the back half of the garage and 1 for the front half so I can only turn on the back section if I'm working in the daytime with the overhead doors open. 12 fixtures total. Same type as yours. 8' fixtures with 4 4' bulbs each. My garage has 6 trusses not including the ends with 2 lights on each truss. The foil backed insulation helps a little as well but white walls should serve the same purpose.

 

[2ManyProjects]

I'm currently having a 30' x 40' x 12' walls with a 4/12 pitch roof metal shop built. I'm going to wire it myself. I'm planning on installing 10, 8' 4-bulb T8's, five on each side running parallel to the 30' sides.

You might want to sharpen your pencil a little on that. No way you're going to fit a run of five 8-foot fixtures into a 30-foot space. You PROBABLY aren't going to fit them into a 40-foot space either, because you probably don't REALLY have 40 feet to play with. Those advertised metal building sizes are typically EXTERIOR dimensions, and nominal ones at that. Besides, you really don't want to go smack up to the walls.

I'll also have 4 skylight panels in the roof. Do ya'll think it'll be enough light for night use. I'll be working on my dirt track car and activities related to that, except I don't drink. Thanks!

The math provided by "bczygan" is more-or-less correct; so you're in the general ballpark in terms of the total number of tubes. But the arrangement you propose could surely be improved markedly. With only two rows of lights, either the space between them will be too large, or the walls will be insufficiently lit.

Depending in part on just what you have available to attach to, I would likely suggest four rows of seven 4-foot twin-tube fixtures, with gaps of about 1.5 feet between each fixture (end-to-end), all running parallel to the 40-foot walls. This would put the end of each run about 3 feet off the 30-foot walls (perhaps a bit less by the time you account for the TRUE interior dimensions); and assuming each row is 7.5 feet from the next one, the outside rows would be about 3.5 feet off the 40-foot walls (again, pending the true interior dimensions) -- so decent coverage for any wall-mounted shelving, cabinets, etc..

This would total 56 tubes; which, at 2,800 lumens/tube, would yield about 156,800 total source lumens. Yes, in theory that's a tad high for 1,200 ft.^2 (it averages out to about 130 lumens/ft.^2); but given the somewhat high mounting (which "costs" you some light at working height, but is good for even distribution) and the less-than-ideal reflectivity of the ceiling & walls, it's NOT too much, as long as you implement the switching properly -- i,e, to control not only zoning, but also brightness within each zone. Point is, you will surely want to run SOME of this even during the daytime; but given the skylights, and the possibly open doors, you WON'T want to run all of it when you don't need to.

 

[spotco2]

I've got a 30x30x10 and only used 20 T8 bulbs (3 - 4' lights on 2 trusses and 2 - 8' lights in the center) and have white walls.

I could not imagine it much brighter inside. You're only 10' wider than me so another 6 or 8 bulbs would do it.

 

[Ray916MN]

I'm using roughly double what bczygan's calculation suggests in my building which is basically the same size as what you're building. Some lighting calculators suggest doubling the number of bulbs that come from a straight output calculation for lighting a surface to account for the fact that fluorescent tubes cast roughly 3/4 of their light up at the ceiling and walls. Fixture mounting height/type of fixture, open rafters, lots of shelving, cars sitting on lifts and surface colors all make a difference between what works in theory (ie comes out of a lighting calculation) and what works in practice.

Here's what 44 small white reflector fixtures with 88 4' daylight tubes surface mounted to a white ceiling looks like.

The 44 fixtures does not include the fixtures mounted under the shelf overhangs to light the areas shadowed by the shelving.

 

[bczygan]

This is a great discussion, and the alternatives and particulars discussed show how different options and details dramatically effect the final result. The range of possible solutions is wide, as evidenced by the responses.
You need to decide on how you will use the space and the lighting levels you want for general illumination and specific tasks.
2ManyProjects points about layout are something to think about. And Ray916MN has a space lit up wonderfully, with no dark corners. I would love working in that space.
Variables that effect the number of fixtures the most are mounting height and whether they have a reflective surface right above them. As mentioned above, how you circuit them will help with daytime or nighttime use.

 

[Steevo]

I used 17 of those fixtures in my 24x40.

 

[2ManyProjects]

I've got a 30x30x10 and only used 20 T8 bulbs (3 - 4' lights on 2 trusses and 2 - 8' lights in the center)

I gather that each of these fixtures have four F32T8 tubes. Presuming that's the case, that works out to only about 62 lumens/ft.^2, even before we deduct for the losses incurred at "working height" vs. their installed height. I would consider that marginal, at best, and downright inadequate for fine detail work and/or folks with less than perfect eyesight (and virtually everyone over 40 falls into that latter category ).

and have white walls.

That helps, of course; but it can't perform miracles.

I could not imagine it much brighter inside.

I'm guessing that you're on the young side, and/or have never experienced truly effective shop lighting.

You're only 10' wider than me so another 6 or 8 bulbs would do it.

No way.

Even 28 tubes, at 2,800 lumens each, would total only 78,400 source lumens. Spread that over 1,200 ft.^2, and you're back to 65 lumens/ft.^2 (again, based on SOURCE lumens). And perhaps even more importantly, with that few fixtures to cover that much space, the ability to light it all EVENLY would suffer significantly.

{image deleted}

Your photo is grossly misleading. The camera's auto-exposure control saw all that dark exterior space in the frame, and tried to compensate for it by extending the exposure. Per the EXIF data in the image, it was shot on an iPhone 4, with the lens wide open (f/2.8) and a 1/15-second shutter speed, with the ISO setting jacked up to 640. (Then you ran it through Photoshop, which further means all bets are off.) Attached is your photo, after bringing the Brightness, Contrast, and Gamma settings down to more reasonable levels using "showFoto" (a Linux-based photo editor). Note that most of the interior (especially the back wall) is still completely blown out from gross over-exposure -- proof-positive that the lighting in there isn't REALLY anywhere near as bright as your photo would imply at first blush.

I'm using roughly double what bczygan's calculation suggests in my building which is basically the same size as what you're building.

Very nice shop! And nicely lit, too.

Some lighting calculators suggest doubling the number of bulbs that come from a straight output calculation for lighting a surface to account for the fact that fluorescent tubes cast roughly 3/4 of their light up at the ceiling and walls.

Any DECENT lighting calculator will take both surface reflectivity AND the photometrics of the particular fixture(s) being used into account. Beyond that, it is at least a gross over-simplification to state that "fluorescent tubes cast roughly 3/4 of their light up at the ceiling and walls." This depends almost completely on the fixtures into which those fluorescent tubes are installed; and even open-tube strip lights direct more of their output downward than upward.

Fixture mounting height/type of fixture, open rafters, lots of shelving, cars sitting on lifts and surface colors all make a difference between what works in theory (ie comes out of a lighting calculation) and what works in practice.

Very true. But you at least have to start with the theory, or you're just throwing darts in the dark, so to speak.

Here's what 44 small white reflector fixtures with 88 4' daylight tubes surface mounted to a white ceiling looks like.

{image deleted}

Again, very nice. How did you get the bikes up on that platform? It does not appear to be a lift.

 

[spotco2]

blah, blah, blah, blah....

I'm guessing that you're on the young side, and/or have never experienced truly effective shop lighting.



No way.

blah, blah, blah, blah...


Your photo is grossly misleading.

blah, blah, blah, blah...

Yeah, I'm over 40. I can see just fine inside the building and nobody else has complained.

Yeah, I took a pic with an iPhone and used Photoshop to resize it. What's your point? I was just trying to point out that not everybody needs 60 bulbs to see what they are doing. We're not doing surgery in the shed, it's just a storage building.

Are you from Ga, because I've worked beside a few smart azz sparkies down here that were electrical Gods and wanted to make sure everybody around them was aware of that fact.

 

[NHBandit]

I gather that each of these fixtures have four F32T8 tubes. Presuming that's the case, that works out to only about 62 lumens/ft.^2, even before we deduct for the losses incurred at "working height" vs. their installed height. I would consider that marginal, at best, and downright inadequate for fine detail work and/or folks with less than perfect eyesight (and virtually everyone over 40 falls into that latter category ).



That helps, of course; but it can't perform miracles.



I'm guessing that you're on the young side, and/or have never experienced truly effective shop lighting.



No way.

Even 28 tubes, at 2,800 lumens each, would total only 78,400 source lumens. Spread that over 1,200 ft.^2, and you're back to 65 lumens/ft.^2 (again, based on SOURCE lumens). And perhaps even more importantly, with that few fixtures to cover that much space, the ability to light it all EVENLY would suffer significantly.



Your photo is grossly misleading. The camera's auto-exposure control saw all that dark exterior space in the frame, and tried to compensate for it by extending the exposure. Per the EXIF data in the image, it was shot on an iPhone 4, with the lens wide open (f/2.8) and a 1/15-second shutter speed, with the ISO setting jacked up to 640. (Then you ran it through Photoshop, which further means all bets are off.) Attached is your photo, after bringing the Brightness, Contrast, and Gamma settings down to more reasonable levels using "showFoto" (a Linux-based photo editor). Note that most of the interior (especially the back wall) is still completely blown out from gross over-exposure -- proof-positive that the lighting in there isn't REALLY anywhere near as bright as your photo would imply at first blush.




Very nice shop! And nicely lit, too.



Any DECENT lighting calculator will take both surface reflectivity AND the photometrics of the particular fixture(s) being used into account. Beyond that, it is at least a gross over-simplification to state that "fluorescent tubes cast roughly 3/4 of their light up at the ceiling and walls." This depends almost completely on the fixtures into which those fluorescent tubes are installed; and even open-tube strip lights direct more of their output downward than upward.



Very true. But you at least have to start with the theory, or you're just throwing darts in the dark, so to speak.





Again, very nice. How did you get the bikes up on that platform? It does not appear to be a lift.

Holy hell dude... Just a bit over the top maybe ? Too much coffee ?

 

[jhochst]

i have 30x48x12 with white metal ceiling. 3 rows of 5 Lithonia T8 8' long 4bulber. Works for me.

 

[sunsation288]

Call me crazy , but for 1000 square foot and 13 feet ceiling , i have 6 x 6 T5 and 2 x 4 T5 ...when i flip the switch i don't need flashlight , all my fixture i can drive one at the time if i wich

 

[hanly2]

This is how I did my 30x40x12. I also went with scissor trusses to give me even more height above the lift. No problems with not having enough light. I wired them so I have 2 switches. 1 for the back half of the garage and 1 for the front half so I can only turn on the back section if I'm working in the daytime with the overhead doors open. 12 fixtures total. Same type as yours. 8' fixtures with 4 4' bulbs each. My garage has 6 trusses not including the ends with 2 lights on each truss. The foil backed insulation helps a little as well but white walls should serve the same purpose.

How tall is your door? And can you lift your car high enough to get another car under it?

 

[shooting4life]

The general rule I learned reading this forum about lighting is figure out how many lights you need, double it, then you will have enough.

 

[Coach529]

24' x 42' with 10' sidewalls and old galvanized tin on the ceiling.

Qty 13, 8' t-8 tandems.

 

[stockcar36]

I put 12 of the aforementioned fixtures in my shop last Saturday. There are six on each side running parallel to the 30' sides of the shop. Luckily my contractor left his scissor lift for me to use. I put them on two switches with each switch operating every other light on both sides. Plenty of light!

 

[theoldwizard1]

A short sidetrack

What is the cost for an average 8' fluorescent bulb versus a 4' bulb ?

How do you transport them if you don't have a long bed pickup ?

 

[zcar751]

I have two 8 foot fixtures in my 24 x 40 garage. I use work lights from time to time when needed. Would more lights be nice sure, will I add more in the future sure.

 

[hanly2]

A short sidetrack

What is the cost for an average 8' fluorescent bulb versus a 4' bulb ?

How do you transport them if you don't have a long bed pickup ?

I think the 8' fixtures mostly use 4 4' bulbs.