Im in the process of rennovating my house, and Im at the point of re-doing lighting on the ground floor.

Im looking at putting downlights in, removing the existing clusters of bulbs.

The thing that I am not sure about is what kind of density or spacing I should have for downlights.

There are two spaces I would light to light independently, both part of an open floor plan. The first is the "living area" and has rough dimensions of 4.5m by 4m, and a dining area which is roughly 2.7m by 1.8m, laid out something like this:

   |  |||||||
+--+        |
|           +--------+
|                    |
|                    |

I have seen suggestions (primarily from one website, as there seems to be little information coming up readily) that the downlights should be spaced roughly equivalent to half the height of the wall, and that you can determine how many you need by multiplying the square footage by 1.5 and dividing by the number of watts of your intended bulbs.

An electrician that I have been using for various jobs has given me a "per fixture" price, so I can basically figure out how many I want and budget the installation myself. But can anyone shed any more light on how to figure this out (excuse the pun)?



I usually approach this (by throwing some light on the subject :) ) by deciding the activity and necessary light level in the areas concerned.



(https://www.noao.edu/education/QLTkit/ACTIVITY_Documents/Safety/LightLevels_outdoor+indoor.pdf - this is more for a professional situation roads, offices etc)

Then once you have that, you can take the output of the light(s) you intend to use and divide light level by lamp output. This gives you the number of lights.

If they don't fit nicely into the space available then find a light with a higher (or lower) output to get a neat number & spacing.

Of course, you can get away with some margin of error on the numbers but do remember that darker walls tend to need more light.

Also consider that if some need to do fine work (needlework etc) in their comfy chairs then the light level needs to be higher - but you can get that with extra lamps.

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  • 2
    "Bring me a comfy chair !" – Alaska Man May 12 '19 at 18:20
  • @Alaskaman I guess you have heard that as well... :) – Solar Mike May 12 '19 at 18:28
  • ...or choose "higher and dimmable" and figure you can dim them down if too bright. But, that does not account for beam pattern, which is often poorly specified as well, so some practical experimentation before going whole hog on buying a bunch of fixtures MAY be advisable.... – Ecnerwal May 12 '19 at 19:17

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