"Mike Saunders" wrote in message
...

If you decide you really must have downlighters, you would do better
to use them for circulation lighting and to use local task lighting
to bring the workstations up to an acceptable light level. I suppose
that, unless they are low energy types, one advantage of using
downlighters to achieve office lighting levels is that you probably
won't need to use any heating in the winter.


From yours and the other threads this seems to be the right idea.
Actually the office is simply a room in my house which I use as an
office (mainly computer) so I may have mislead re the reqts. Assuming
a 'normal' genaral purpose reqirement plus task lighting for the
computer What would you suggest for the downlighter rating and numbers

What sort of downlighter do you want to use? The alternatives are broadly -

Halogen downlighters - small, but highly directional. Likely to create
strong pooling of the light and to make the ceiling look dark. Ratings
available from 10W to 50W. Using lots of low power ones will give a better
spread of light than a smaller number of high power ones. Flood types will
also give a wider spread of light than spot types. IMO the suitable only use
for halogen downlighters is display lighting, or where you need a very local
light.

Mirror spot reflector lamps, usually around 50-65mm diameter. Ratings
available from 40W to 60W. These can be used in much the same way as halogen
lamps, but they give a light that is not so strongly directional.

PAR 38 spot or flood lamps. Rather old fashioned now, but the large diameter
does give a much better spread of light, particularly if you use the flood
version.. Ratings available from 60W to 120W. I have used four to light a 3m
x 4m kitchen.

Low energy downlighters. Usually the largest diameter fittings (the ones I
have are 135mm), but they are the only lamps that do not also produce
significant heat and they normally have the most diffuse spread of light.
Ratings available from 9W to 35W.

Colin Bignell