Light density calculator?

["JonShaw" <semi.jon@xxxxxxxxxxxxx>]

When sizing heating radiators a calculation of the room's losses is
made and
combined with a target temperature based on the room's usage a radiator
size
can be calculated.  I knocked up a spreadsheet to do this for our bedrooms
and even in the coldest weather this winter all rooms were fine :-)



In the lighting world is there a similar calculator that enables one to
calculate the density of light fittings required dependent on the height of
the room, the activities (like reading) planned and the output of the
fittings?

e.g. I assume that the pitch of downlights changes if 35W units are fitted
instead of 50W; or if a central or linear  fitting is used rather than 2D
downlights.



If there are no calculators are there "rules of thumb"?



Also are there good estimates of the different light outputs of differing
bulb types, (incandescent, CFL, LED).  I think the standard unit would be
lumens (?), but the defacto seems to be "incandescent watts
equivalent".





I have a corridor, kitchen and dining/family/TV room to light, I am
considering a "lighting design" for the multi purpose room, but
think it
overkill for the other areas.

TIA



Jon



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