Lighting Lux Levels

[uksparks]

Hi,

Does anyone have any documents that they are aware that are 'reliable' levels as far as lux goes?

Basically im just looking for a nice document, or information i can take and re-type to keep in a folder for light levels.

The documents and pages I have found all conflict and have significantly different levels for the same things, so I don't really know whats right etc...

• Ergonomic Lighting Levels by Room - Minimum Lighting Levels for Residential Spaces
• http://www.wbdg.org/pdfs/usace_lightinglevels.pdf
• Lighting Levels
• View attachment Required_Light_LevelsEN.pdf

The last one seems like a nice document, but just don't know how good any of the data is?

I don't want it for any particular reason, just nice to have, things to show customers when they say 4 down lighters in a bathroom is enough and I say you want more etc, that type of thing...

Thanks

 

[mark80]

You won't find a document that says 4 down lights for a certain size room if that's what you're after? Only way to prove is to calculate either manually or using a software package, which would be pretty mad IMO for a domestic environment. A reliable source used in industry for lighting levels is CIBSE SLL code for lighting, which off the top of my head states 150lux for toilet areas. CIBSE guide A has a general guide for levels for domestic I think

 

[mark80]

Looked in CIBSE guide A for you and it states for a dwelling:

Bathroom - 150lux
Bedroom - 100lux
Hall/Stairs etc - 100lux
Kitchen - 150-300lux
Living room - 50-300lux

 

[uksparks]

What I was after is something that suggests minimum recommended lux levels really, not how many down lights you need.

I can work it out, but it was just a case of having a document that said, ideally you need X lux in a bathroom, kitchen, office etc...

 

[Chr!s]

What I was after is something that suggests minimum recommended lux levels really, not how many down lights you need.

I can work it out, but it was just a case of having a document that said, ideally you need X lux in a bathroom, kitchen, office etc...

Cibse hase the best lighting guides, different guides for different applications

 

[atm84]

Yes CIBSE guides are the best. Get a copy of the SLL guide which has lux levels for many different environments. So out of curiosity how do work out how many lights are required to achieve a particular lux level without calculating it with software?

 

[uksparks]

I don't really know at the moment as it's not something I've really looked at mainly doing domestic.

i would imagine each lamp has an output level etc that you can calculate it from?

what software is there that you can use then?

 

[atm84]

Dialux is one of the best and is free. The output of a lamp is given as lumens but you are measuring the lux level which is the amount if light that falls on an area. This is dependent on type of light fitting, type of lamp, type/ coulour of surfaces, height of fitting. There are many factors to consider. Its a science to even know where to begin trying to do it by hand and something which us only taught at university level. You are better off downloading the software and getting some training from a lighting manufacturer how to use it. It appears easy at first but to be able to appreciate the full benefits you will undoubtedly require some level of training.

 

[uksparks]

Thank you, I'll take a look at that and let you know.

 

[Richard Burns]

Found this one at one time from somewhere,
pretty sure the tables will mess up but...
It may help?

Lighting Calculations
How Many Fittings are Required for a Room
The utilisation factor table and a few simple formulas allow us to calculate the number of fittings required for any room.
Step 1: Understand the utilisation factor table that is available on most fittings.

UTILISATION FACTOR TABLE (for 2x36 bare batten)
LOR: 88.1%	SHR NOM 1.75: 1.0	Disregard SHR MAX.
Reflectance	Room Index (K)
Ceiling	Wall	Floor	0.75	1.00	1.25	1.5	2.0	2.50	3.00	4.00	5.00
0.50	0.30	0.20	0.30	0.37	0.42	0.46	0.52	0.56	0.59	0.63	0.66

Across the Top of the Table

Name	Description
LOR	Light output ratio for this fitting. Not required in a simple calculation.
SHR NOM	Nominal Spacing to Height ratio. For a given mounting height we can see the nominal spacing between fittings. Eg. 1.75 to 1 means that for every 1 metre of mounting height (above work plane) we should have a maximum 1.75 metres between fittings.
SHR MAX	Used by lighting design software and not needed for manual calculations.
Reflectance	Select a horizontal line for the reflectance values that best describe the room.

Typical Reflectance Values are:

	Ceiling	Walls	Floor
Air Conditioned Office	0.7	0.5	0.2
Industrial	0.5	0.3	0.2

Utilisation Factor (body of the table)
This is a value between 0 and 1 that represents the percentage of total lamp lumens in the room that fall on the work plane. It takes into account the room reflectances, room shape, polar distribution and light output ratio of the fitting.
Step 2: Calculate Room Index (K)
Room Index:
The room index is a number that describes the ratios of the rooms length, width and height.
Formula: K = L x W
_____________
Hm (L+W)

Where: L = Room Length
W = Room Width
Hm = Mounting Height of Fitting (from working plane)
Work Plane = Desk or Bench Height
The result of this calculation will be a number usually between 0.75 and 5.
Note: This formula for K is only valid when room length is less than 4 times the width or when the K value is greater than 0.75.
Step 3: Using the room index and reflectance values in the utilisation factor table
For the horizontal row select the reflectance that best describes the room.
For the vertical column select the room index value K as calculated above.
The utilisation factor for this fitting in this room is where the row and column intersect.
Step 4: To calculate the number of fittings required use the following formula:
Formula: N =E x A
____________
F x uF x LLF

Where:	N = Number of Fittings
	E = Lux Level Required on Working Plane
	A = Area of Room (L x W)
	F = Total Flux (Lumens) from all the Lamps in one Fitting
	UF = Utilisation Factor from the Table for the Fitting to be Used
	LLF = Light Loss Factor. This takes account of the depreciation over time of lamp output and dirt accumulation on the fitting and walls of the building.

	Typical LLF Values
Air Conditioned Office	0.8
Clean Industrial	0.7
Dirty Industrial	0.6

	Standard	Triphos
Lumen outputs of fluorescent lamps	18 Watt / 1150 Lumens	1300 Lumens
	36 Watt / 3000 Lumens	3350 Lumens
Lumen output of PL lamps	18 Watt / 1200 Lumens
	36 Watt / 2900 Lumens

Step 5: Space the number of fittings uniformly around the room drawing and check the SHR nominal for the fitting has not been exceeded. If it has been exceeded re space the fittings to get back to SHR nom.
Step 6: Work out the number of fittings required in each axis of the room:

Number in Length =	Root (Total * L/W)
Number in Width =	Root (Total * W/L)

 

[uksparks]

Thanks Richard, I'll copy this down into Word and try to get my head round it. Cheers

 

[mark80]

Manual method as per above! I've done a comparison between manual and software based lighting calculations and TBH I found little difference between them for ceiling mounted fittings. The software uses the same method to calculate with obviously more precision in areas as the software can do 3d modelling to ensure consistent light levels across the entire room. Only really need the software for everything other than domestic IMO.

As above, you can get dialux and relux for free and they're excellent packages. I prefer relux as it can be incorporated into a CAD drawing but it's more complicated to use than dialux. If you knock up a spreadsheet with the above formulas you'll be able to enter the size of the room and lux level etc and the spreadsheet will calculate the rest for you.

 

[atm84]

Dialux can also be incorporated into Dialux and is far superior than Relux.