is there an guideline amount of lighting based on room size?

[tan8856]

hi

i have a lounge/diner that is 27' x 12' and cant find anything on the net about recommended amount of ceiling lighting for a room based on its size.

i currently have 2 ceiling lights in there, each has 3 x 40w bulbs. the room seems a little dingy though when all the lights are on. i could up it to 2 lots of 5 x 40w but isnt 400w a bit excessive for a 27 x 12 room?

does anyone one have any advice or can you point me in the direction of some guidelines?

 

[PrenticeBoyofDerry]

There are calculations that can be made regarding illuminance.
this link may help a little way to the understanding of it.
http://www.acl.co.uk/light_level.htm

 

[tan8856]

There are calculations that can be made regarding illuminance.
this link may help a little way to the understanding of it.
http://www.acl.co.uk/light_level.htm[/QUOTE]



can anyone simplify?

 

[PrenticeBoyofDerry]

How simple do you want it?
Illuminance is calculated by using what is called the inverse square law.
This takes the point at which the source is (The Lamp) and it's luminous which is measured in the SI unit Candela(cd), the spread of light is known as illuminance and measured in the SI unit of Lux(lx).
If the power source was one Candela and it hit a flat surface one metre below it, the light spread over this surface would be one Lux over one square metre, if the same power source(one cd) hit a flat surface 2m below it, the Lux value would then be one quatre the value of the value at one metre. As the flat surface area now covered would four square metres.
Remember light doesn't tunnel straight down, it spreads out in a pyramid effect from the source.
So the further it travels the weaker the brightness gets, even though if you added up the Lux values per square metre covered, it would equal the value it was at 1 metre distance from source.

If you had more than one light source, this would also be calculated into it if the light from these sources crossed each other, then a bit of trigonometry will be required.
So the guidelines are roughly;
Casual vision=100 lx
Reading and Writing=500lx
It's not a particular easy subject to explain and difficult to simplify, if you wish to understand it.

 

[1john]

keep adding extra lamps until you can see

 

[PrenticeBoyofDerry]

keep adding extra lamps until you can see

That about sums it up

 

[MisterG]

Hi

If you don't need to dim the lights you could get a 5 bulb fitting and fit low energy bulbs.

I've got a 5 bulb fitting each at 20W, equivalent to 500w incandescent. Probably a bit too bright, but two times 5 x 8w would give you 400w equivalent, but only use 80 watts of power.

Aternatively just replace the existing bulbs with a higher illuminance. E.g. 40w = 8w low energy, so replace those with 60w equivalent bulbs (12 w low energy) and that will give you more light.

If you do need to dim the lights you can still get low energy bulbs, but these are much more expensive.

Regards

G

 

[PrenticeBoyofDerry]

who was dimming lights?

 

[MisterG]

who was dimming lights?

Hi

I meant if he hasn't got a dimmer switch, then he can use ordinary low energy bulbs.

As ordinary low energy bulbs, (which are cheap) arenot meant to be used with a dimmer switch.

A dimmable low energy bulb is usually over ten pounds, so would make it more expsnsive to fit.

Regards

G

 

[PrenticeBoyofDerry]

To be honest if think the OPs is still working out the inverse square law,
I was pulling your leg that's why the shades

 

[Stoday]

The inverse square law does not apply to lighting in a room. The reasons are

1) Light reflects from the walls, ceiling, floor and furniture. Dark walls etc will reduce light levels in a room.

2) The luminaire (light fitting) modifies the distribution of light. Some lights form a beam, others flood the room.

If a room appears too dim, add more lights. Up to around 500lux. More than 500lux and you have to control the glare with more expensive luminaires.