Which is brighter

andrelaplume2May 24, 2011

In my basement, I am deciding on the typical 2 x 4 3 tube T8 flourecent lights for dropped ceilings...the ones with the plastic insert to hide the bulbs and a new offering at HD....parabolic 2 x 4 flourecent lights.....these also have 3 - T8 bulbs...they sort of look like the ones you see in offices.....which type provide the most light?

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David

Both should be about the same.

FYI, the Cree CR24 LED fixture is going head to head with fluorescent troffer lights. You may want to check it out to get an idea of other available options.

Here is a link that might be useful: Cree CR24 description.

    Bookmark   May 24, 2011 at 12:27PM
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andrelaplume2

the parabolic have a nicer look and do not seam to create as much glare...but there will be a ping pong table nearby so we need light. I also notice these lights are coming with 3 - T8 bulbs instead of 4 of the older 1.5" bulbs...I assume the older ones threw off more light...or no....ie do I need an extra fixture...is tehre a rule of theumb for how many of these 2 x 4 fixtures are needed for so many sq ft?

    Bookmark   May 24, 2011 at 4:25PM
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David

An easy way I use is to divide the total light output over the room size and compare the result with a desired lighting per sq ft number.

For example, assuming that you would like to have ~ 30 lumens per sq ft and the room is 20'x 10'

Total light required for the room would be 30 x 15 x 10 = 6000 lumens.

Assuming each T8 tube provides ~ 1500 lumens, the fixture should provide 4500 lumens.

In this example, you will be short of 1500 lumens (1 tube).

The calculation is a very simplistic means of figuring out general lighting and does not take into account distance from the surface to be illuminated, light trapped in the fixture or shadow regions.

    Bookmark   May 24, 2011 at 6:31PM
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andrelaplume2

whats an avg lumens per sq foot.....in the example above it would seam that would be pretty dark....30 lumens per sq ft that is..

    Bookmark   May 25, 2011 at 11:35AM
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David

On the contrary, it is quite bright.

I used 35 lumens per sq ft (which was close to the output from the original T12 lamps divided over the area) to calculate the number of lights needed for my kitchen.

You can do the calculation with your existing fixture.

    Bookmark   May 25, 2011 at 1:03PM
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andrelaplume2

well the one half of my basement is about 10 x 20 and having one 4x8 3 bulb light just seams like it would be real dim....even two sounds dim...I'd think 3 but then thats 9 T8 bulbs....they seam to have 2.5 - 4 x 8 fixtures every 200 sq ft here at work...though they only appear to have 2 bulbs each....but we have windows as well.....

    Bookmark   May 25, 2011 at 5:51PM
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David

A 2x4 fluorescent troffer has ~ 4000 - 6000 lumens output, depending on the number of T8 tubes used.

That works out to
20 - 30 lumens per sq ft.

    Bookmark   May 25, 2011 at 7:41PM
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DavidR

I would guess that the parabolic reflector will be more efficient at getting the light out of the fixture.

I'm not familiar with this particular product, so this may be an unjustified comment, but beware of the low quality in some of these store-brand big box products.

    Bookmark   May 26, 2011 at 9:24PM
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lee676

Most 4 foot T8 fluorescent tubes are brighter than that - the better-quality (82-86 CRI versions) typically closer to 3000 lumens. The type of ballast you use also affects brightness (look for "ballast factor" - a ballast factor of 1.00 means you get the lumens specified for the bulbs you use, but a B.F. of .85 on "energy saving" ballasts mean 15% less light. Some go the opposite direction, a ballast factor of about 1.20 which increases brightness by a like amount (but also increases energy use and shortens bulb life).

    Bookmark   May 27, 2011 at 4:59PM
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