Is there an equation for calculating the amount of lighting required to a room?
I believe there is as I have done this calculate before, I am just struggling to remember it!!
Many thanks
Answer:
I will have to check in work tomorrow in a book i have been given by thorn lighting. but the lux level will alter according to the height of the celling and is the required light level at floor height . personally id cheat and ask a manufacturer how many fittings I would need to buy and let them work it out .
added later
my boss has chucked the book he now does it on the PC with some program he was bought .
There are a couple ways to calculate the lighting required. I have used the room cavity ratio method. I suggest you contact a lighting manufacturer. They will be more than happy to help you.
Provided your ceiling height is in the normal range, for a room as large as you state, a coefficient of .5 is not unreasonable, and .8 indicates some kind of discharge lighting, and is also reasonable unless there is a dust factor.
I'm not familiar with lux., but in foot candles, (Lumens / Sq. Ft.) the calculation would go:
No. Fixtures x No. Lamps/fixt. x initial lumens/lamp x CU. x MF. / area (in Sq. Ft.)
Hope that helps.
best bet is to use a lighting package.
since it will depend on reflectance values, windows, ceiling height luminaire type and efficacy etc etc,
based on a 3 mtr ceiling i get 4x5 (20) No 4x18w lamps 600x600 recessed moular fittings @477 lux
or 5x5 (25) No 3x18W lamps 600x600 recessed modular @517
utilisation factor of 0.5 is quite low?
check out the relux web site
or send me an e-mail on mark_gardiner_spcs@yahoo.com
let me know the type of area, ceiling height and type of (luminaire make or type if you know) and i will forward a calc?
I wouldnt bother working it out mathematically as there are a number of variables which mean you cant calculate it accurately without photometric data and serious integration.
rules of thumb are okay but I wouldnt put money on them.
I would ask for example, Thorn lighting for a catalogue - they have the info in there to help you devide, there are too many variuables for a simple calculation, for example
Dimensions of the room
Colour of the floor, ceiling, walls
What is in the room (to work out all the room is suitably lit, you need to consider this), and their colours (light relfecting)
Type of light fitting
Windows and outside lighting
So many variables..
We got some software called Traclite or Traclitestar from Trac lighting - works it all out for you. You can draw the room, fill it with stuff (even lorries or airplanes are in the library with it!!), coour it and all sorts and it calculates for you. You can even get a display of the room, spin it round and see the shadows - try ringing them (search internet for address) and say you are interested in their stuff and ask if yo can have the software (it only has there lights on it though)
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