Number of (fluorescent) lights in a room

Just a quick one.
Does anyone have any information about calculating how much light to "put into" a room? The room in question is 6.5m by 3.1m and will be used for "conference"-type meetings; round-table discussions and presentations to small groups of people in daylight and at night time.
The people in question will probably use standard 5ft or 6ft tubes at least initially. They may, later, wish to change these to something less industrial or possibly add up/wall lights, but let's ignore that for now.
Intuitively I would have thought 4 or 6 tubes (1-tube fittings) switched in banks of 2 or 3 would do the trick - high level of even light for round-table meetings and the possibility of switching off a bank or two for use with OHPs etc.
Does anyone have any better suggestions? What about the colour-balance of the tubes?
TIA
Hwyl!
Martin.
--
Martin Angove: http://www.tridwr.demon.co.uk /

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snipped-for-privacy@tridwr.demon.co.uk (Martin Angove) wrote in message

Hi Martin.
Personal preferences vary, ditto colour of walls, level of light needed for differenr jobs... tough one to calculate. I have studied approaches to numbers/calculations, but I dont think I'd follow them to be honest. I cant help thinking someone was trying to simlpistically sciensce-ify something with too many real world variables.
Once you've started with an initial estimate its easy to put wires on the fittings and stick them up temporarily to see what it looks like.
If you want comfort I would really go for 4' not 5'. Personally I'd start with say 4x 4' fittings for a white painted room that size, with the tubes pointing up, not down. I.e. either shelf, trough or even suspecnded fittings. That is one of the most important faetures of any fl light installation. Unfortunately most are still being installed pointing down.
Another important is switching: a switch for every light, then you can make sure you're always comfortable, and not waste money/energy. Comfort is important in work situations, and is an issue with many fl installations.
The last important is use any colour of white you like, but _dont_ ever touch cool white or 4500K. As long as you avoid those 2 horrors anything else is usually fine.

6' hasnt been standard for a long time.

Too high, too little control. But this is all too common, carelessness design seems to be the done thing with fl lights.
Regards, NT
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The ceiling height matters, but say 2.5m.
using 6 off 5' singles with 3500K triphosphor tubes on a 3x2 grid, longwise dowmn the room, will give about 700 lux across the room at table level, except for the 2' nearest the walls.
This is a bit bright for what you need, so go for what other posters have said and use DL's for the table; and 4' tubes.
If the ceiling is much higher than 2.5m then you'll need to consider louvred fittings to reduce the glare along the length of the room, and recalculate!
Hwyl dda.
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