lights per sq foot

[paul b b]

evening all,

how many lights or wattage do you allow per sq foot?

thanks

 

[SPECIAL LOCATION]

Strictly speaking you would do it using your Lux & lumen values.

e.g.

http://www.tlc-direct.co.uk/Technical/DataSheets/Illuma/LightLevels.htm

you have to take into account the height of the light source from the area of illumination!

It's back to them college calculations to work it by the book!

 

[Lurch]

how many lights or wattage do you allow per sq foot?

Depends on where, when and why, and also with other factors thrown in, like available natural light etc... Far too vague a question, there is no fixed watts per foot that applies to everything.

 

[paul b b]

Depends on where, when and why, and also with other factors thrown in, like available natural light etc... Far too vague a question, there is no fixed watts per foot that applies to everything.

is there not a genral guide line.

how many down lighters would you put in a room 4m x 4.5m

 

[Lurch]

is there not a genral guide line.

Not really. Differnet types of light do different things so a 100W GLS is not the same as 100W of downlighters.

how many down lighters would you put in a room 4m x 4.5m

It would depend on the room and what it is to be used for, and what else is in it, so like a gloss white kitchen with white walls, floors and ceiling would probably need less light than a dark oak country kitchen with dark red walls and quarry tiled floor.

 

[paul b b]

thanks lurch, i understand that, but was hoping that there was rule of thumb, like 2watta per sqfoot or something. oh well back to guesing lol.

thanks anyway

 

[batty]

4 should be enough.

 

[tom1]

4 should be enough.

and its usualy easy to add another one in the centre later if need be

 

[SPECIAL LOCATION]

thanks lurch, i understand that, but was hoping that there was rule of thumb, like 2watta per sqfoot or something. oh well back to guesing lol.thanks anyway

To add to Lurches comment about all the variables that would be in the mix...

and as I said earlier earlier the amount of light is from the lumens NOT the wattage. The Wattage is how much power it consumes to create that light.

With modern energy efficient lights, ideally should give at least 40 lumens per watt. (thats stated in Approved doc LB1)

Comparing a few examples:-

Your old typical 100watt GLS bulb was around 1300 lumens (13 lumens per watt!!! :_| )

Or

A traditional 300w halogen bulb is around 3000 lumens (10 lumens per watt)

Whereas you can get your energy saving bulbs such as:

11watt giving 575 lumens (52 lumens per watt)

Or

9watt giving 450 lumens (50 lumens per watt)

Now that reference sheet from the TLC website suggests

a Kitchen should have 300Lux at the work surface.

whereas a bedroom only needs 50 - 100 Lux

And you have to remember...

An illuminance (Lux) on a surface is also related to the distance that the light is from that surface...

So a hanging pendant will be lower than a ceiling mounted spot light!

Remember Lux is a measure for illuminance of a surface:- where 1 Lux is equal to 1 Lumen per square meter

The basic rules goes something along the lines of:-

A lamp mounted 1m above a worktop

with an output of 1 Lumen

would give 1 LUX illuminance onto the worktop.

If the Lamp was mounted 2m above worktop Lux would be (Lumen/4)

e.g.

500 lumen lamp 2m from surface gives 125 Lux at surface.

Inverse square rule says if you raise it another meter the Lux is (Lumen/9)

You then also get into the realms of reflected light etc..

Overlapping light sources...

so to summaries factors include:-

1/ Lumen output of the lights.

2/ How many lights.

3/ Direction the lamps are pointing. (up / down)

4/ Ceiling mounted or pendants.

4/ Type and use of room.

5/ Amount of reflected light.

Not forgetting....

6/ How much the customer is prepared to pay!!!!!!

etc..

etc..

Within Domestic it is a bit of general guess work with a dab of experience thrown in.

but

In commercial, (with H&S implications in some environments), It may be that you need to verify your design calculations to prove there is sufficient light for a particular work environment.



Dunno if that has helped to de-muddyfy the water?

Or just messing things all up even more! :^O

Blushing

 

[Lurch]

For the commercial lighting plans there's a decent program I have used to do some decent lighting plans and designs. Can;t actually remember what it's called though, fairly certain it was free.

Dialux I think it was, job for this afternoon, download and reinstall that.

 

[Evans Electric]

Regarding the downlights , I'd put 6 x 50w G10s in Paul bb,s room. 3 in each row, with one on the centre line then 1mtr apart.

Deke

 

[bengie]

so my 10w LED bike lights with 900 lumens output are decent then

 

[Andy™]

For the commercial lighting plans there's a decent program I have used to do some decent lighting plans and designs. Can;t actually remember what it's called though, fairly certain it was free. Dialux I think it was, job for this afternoon, download and reinstall that.

relux

 

[Lurch]

Regarding the downlights , I'd put 6 x 50w G10s in Paul bb,s room. 3 in each row, with one on the centre line then 1mtr apart.

For kitchens I tend to end up with 3 rows, or sometimes 2. The outside 2 I put around 600mm from the outside edge so the light falls on the worktop from above rather than from behind creating shadows, and then a\some row(s) in the centre to fill space if required, possibly offsetting them from the main lighting so if there's say 6 up the edge maybe put just 4 or 5 in the middle.

[quote name='Andy

 

[SteveH37]

I have used relux a number of times in commercial, works well and looks professional when printed out. Takes a bit of getting used to but is free with good support from manufacturers.

 

[PC Electrics]

Regarding the downlights , I'd put 6 x 50w G10s in Paul bb,s room. 3 in each row, with one on the centre line then 1mtr apart. Deke

I'd agree with Ev. As a "rule of thumb" I generally start with a 1m grid and put a light on each corner.

Obviously your exact positioning will be dependant upon where the joists are - we don't want to see any more pics of cut out joists!

I also tend to use lamps with a wide beam to give more light spread, especially for kitchens and lounges. Try Sylvania Hi-Spot ES50 with a 50 deg beam, product code 0021261.

 

[Andy™]

I have used relux a number of times in commercial, works well and looks professional when printed out. Takes a bit of getting used to but is free with good support from manufacturers.

take a lot of getting used to! i can do basic designs with it, but thats it

 

[Lurch]

[quote name='Andy

 

[Andy™]

i can get it to work in a room etc, and get the printouts to go with it, which does look good to the customer. but i havent really spent any time with it adding other stuff into the room etc, like furniture, windows etc

 

[Lurch]

[quote name='Andy