Shop Lights

[nitroracer20]

Hey GJ

Quick one - doing my shop lights in my garage.

Roughly 23x23 shop - 10’ ceiling

I have 6 rafter ties spanning garage width. i want to install 2 - 4’ shop lights on each rafter tie.

10K lumen too crazy? I have power at each rafter tie ready. I was thimking linkable units, but would hardwire no problem.

Thanks - not trying to beat a dead horse - just looking for input from people who had similar shops.

 

[kbuhagiar]

Hey GJ

Quick one - doing my shop lights in my garage.

Roughly 23x23 shop - 10’ ceiling

I have 6 rafter ties spanning garage width. i want to install 2 - 4’ shop lights on each rafter tie.

10K lumen too crazy? I have power at each rafter tie ready. I was thimking linkable units, but would hardwire no problem.

Thanks - not trying to beat a dead horse - just looking for input from people who had similar shops.

My garage is lit like an operating room, and I love it.

IMHO too much is just enough, especially over the age of fifty.

When you young'uns start losing your vision you'll know what I mean.

 

[racecougar]

My opinion: 10k lumens isn't enough for that space, assuming it will be used as a workspace and not just a place to park cars. That is only 18.9 lumens per sq ft.

This is just over 60 lumens per sq ft with 13' ceilings.

 

[May Pop]

Just to add my opinion I would start with 5 4 foot fixtures on 3 of the rafter ties. This gets you light to the walls.
With a 5000K lamp or LED this will make it almost like day light.
See how Racecougars walls and floor are illuminated nicely.
It make it easy to work in a nicely lit shop.
Ron

 

[dave*99]

Run one of the free lighting calculators. I used one from Acuity.

Pick a level of illuminance (typically expresses in footcandles) appropriate for your planned activities.

See the plan here:

Lighting for 24x28 shop

So I think I'm off to a rocky start..... I've been reading the best light fixture ever thread for a long time. And I still think I need some help. The basics: Woodshop above garage. Under construction. I have some woodworking machinery to go in the shop. It will have drywall finished...

www.garagejournal.com

I designed for 50 footcandles on the top of the workbenches.

I used 2x4 LED panels. The panels produce 6000lm each. I have 8. So 48000lm @11' ceiling height in a 24x28 room. It came out to 54fc at workbench height.

 

[Shiftless]

Lumens per square foot of floor space is a very rough measure of how bright the space will be.
But with that said, I bet that the OP will have a lot more than 10,000 lumens total if he installs 12 four foot twin tube fixtures. Those are usually about 4000 lumens each.

 

[racecougar]

If that's the case, we're looking at ~90 lumens per sq ft. Yeah, that will be awfully bright. 1.5X of what I've shown above.

 

[dave*99]

It's hard to judge light levels from a glance. I used a free light meter app on my phone to measure light levels on the top of my table saw in my old shop. It's one of my favorite places to work because the light level under that old 2 tube 8' HO fluorescent fixture seems just about right.

I measured 50 fc so I designed the new shop to that same level. They will be dimmable, so I can have some flexibility.

 

[May Pop]

You have to also consider the material that the walls are covered in. If just studs it will not reflect any light and more will be needed to see in the corners and along the walls.

Ron

 

[cybrdyke]

"Lumens per square foot" means absolutely nothing. It's not a metric that's used in lighting at all, and if used will certainly lead you into trouble.
CD

 

[dave*99]

^^^ That's from a true lighting expert. Take heed.

 

[Leaflessshadetree]

I have 9 in my 20 x 20 garage. It's OK to work in, not even close to too bright. I don't do much work there but when I do I think about adding a couple more, maily to get more light where the car blocks it.

 

[racecougar]

"Lumens per square foot" means absolutely nothing. It's not a metric that's used in lighting at all, and if used will certainly lead you into trouble.
CD

One foot-candle equals one lumen per sq ft. I could change my post above to state 60 foot-candles, but I figured it would be easier to understand the calculation if left it as lumens per sq ft.

Yes, ceiling height, reflectivity of surfaces, fixture distribution, and more all play into the level and quality of illumination. My understanding of the OP was that the goal was to get a general idea on whether 10k lumens was enough for a 23x23 garage. IMO, no matter what factors you throw at it, that isn't enough lighting for the space if the space will be used for much more than just parking vehicles. Now if we're talking about 48k lumens as Shiftless pointed out, we're at the other end of the spectrum. Unless the walls and ceiling are flat black, I would expect it to be quite bright with twelve 4k lumen fixtures.

Just my two cents.

 

[cybrdyke]

One foot-candle equals one lumen per sq ft.

That's only 1/2 of the definition. It doesn't mean that you can take the lumen figure from your lights and divide it by your square footage to get foot candles. It doesn't even remotely work like that.
CD

 

[racecougar]

Please read past the first sentence in my post above.

 

[Shiftless]

When we moved in to our current house in 1984, the 20x20 garage with unfinished walls and ceiling was illuminated with one porcelain fixture holding a bare 100 watt bulb.
A fresh 100 watt Incandescent bulb is good for about 1600 lumens. Do the math. 400 sq. ft.
Apparently that was considered adequate for just parking cars back in those days. The former owner was not poor by any means.

 

[racecougar]

When we moved in to our current house in 1984, the 20x20 garage with unfinished walls and ceiling was illuminated with one porcelain bulb holder with a dirty 100 watt bulb screwed in.
A fresh 100 watt Incandescent bulb is good for about 1600 lumens. Apparently that was considered adequate for just parking cars back in those days. The former owner was not poor by any means.

The attached 2-car on my house was that way when I purchased it in 2018. Everything else about the house was over-engineered and over-adorned. The previous owners lived like this for 25 years! We only use that garage for parking two vehicles in, but it has ~31,200 lumens now (just over 60 lumens per sq ft) with white painted drywall walls and ceiling.

 

[dave*99]

^^ And I have no idea how bright 31,200 lumens is in your garage.
But if you said you had 50fc at workbench height I’d know exactly how bright it is.

 

[Shiftless]

I now have 9 twin tube LED fixtures on the ceiling @ 4000 lumens each.
And 3 floodlights over one 7 foot workbench @ 1500 lumens each
And 4 smaller floodlights illuminating a 12 foot wide shelving system @ 750 lumens each
One switch for the floods and one switch for the overheads.

So that’s 43,500 total lumens
The walls are open studs and the ceiling is open joists and the floor is 70 year old bare smooth concrete so reflectivity is very low.

This thread has motivated me to take some brightness readings.

 

[racecougar]

^^ And I have no idea how bright 31,200 lumens is in your garage.
But if you said you had 50fc at workbench height I’d know exactly how bright it is.

60 fc

How high is your workbench?

 

[cybrdyke]

60 fc

Not if you have 60 lumens per square foot.
CD

 

[racecougar]

Maybe it would be beneficial to share the equation? Or nah...

 

[racecougar]

Online calculators point to 60 fc:

 

[dave*99]

Maybe it would be beneficial to share the equation? Or nah...

See post 5.

 

[racecougar]

See post 23.

 

[dave*99]

Luminous flux vs illuminance.

 

[cybrdyke]

I=L1*Cu*Llf*/A
To find the value to plug in for Cu, first you need to now RCR. To find RCR, use the formula 5Hrc*(L+W)/(L*W). Of course, you'll also need to factor in ceiling cavity and floor cavity coefficients. So for those use the formulas 5Hcc*(L+W)/(L*W), and 5Hfc*(L+W)/(L*W). For the cc and fc rates, refer to the IES handbook chart and then refer to the fixture manufacturer's spec sheet or photometric sheet for further data. To be fair, not all the manufacturers make this information readily available. Of course for the Llf value, it would depend on environmental factors such as dirt, dust, moisture, voltage, heat, etc....typically this value is around .7 to .9 .

 

[cybrdyke]

Racecougar,
I'm messing with you, of course, but that IS the formula. Lighting is a science and people have spent years at university studying it and getting degrees and earning fancy letters after their names. There are thousands of people that have dedicated their lives to the science of light. To just reduce it down to saying that you can divide lumens by square feet, not only is not true, it's also an insult to those people that who work in that field professionally.
As for the online calculators...well...you got what you paid for them.

Just an FYI- typically when you do the lumens/sq ft calculations, you'll end up about 30% off target. As Dave*99 tried to show, he measured around 80lm/sq ft, but got 54fc. So please dont perpetuate the wrong info.
Thanks for having a sense of humor.
CD

 

[racecougar]

Thank you for posting actual information.

For the OP, should he still care, I just measured 65 fc in my shop and 51 fc in my garage, both at 39” from the floor. The shop ceiling is 12’7” and the garage is 10’2”.