You can convert T8 lighting to take T5 Bulbs - much cheaper.http://www.saveiteasy.co.uk/electronic-ballast-conversion-units.htm

An light and motion system based on zones would seem the most sensible.

A good control system will also reduce lighting loads in the summer and save on cooling requirement to remove excess heat from the offices.

Thanks for the link Nigel. Its a nice quick way to do it without having to wire in a new ballast. Less automation potential (ie.e .no dimming) but will include several cost scenarios in the business case.

I've also been reading more on this - a good ideas seems to be cut down the overhead lighting to minimum legal levels, (300 lux I think it was) and just have 500 lux over the walkways. Luckily this is possbile due to the way the banks are arranged. Then you can add "angle poise" lamps over the work areas, which people turn on individually. The advantage of doing this is that light level falls off in proportion to distance (twice as dim at 2m as it is at 1m) so bringing the light source closer to the desk means a lower wattage can be used. In my office, the desks are usually occupied about 60% but the bank occupancy would be 100%. So cutting the overhead and going individual would work better... as long as people turn them off when going to meetings! I can see see us needing countdown timers on them :-(

The other think seems to be have an internal light sensor for each bank so lights can follow the sun. Although today we do need all the banks on.

Stephen - The idea of timer is for the corridor lighting - where it would always be dark, but there are actually 2 light circuits - one to maintain a minimal background level - and another day time which doubles the light output. So the second circuit could be on a timer. The seasonal timer can be used for external lighting like pathways etc, but yes - i think these are best left to light sensors - then they would also work during an eclipse, or volcanic eruption ;-)

Toilet lights need PIR sensors and probably an "occupied switch sensor " too, as I found out the 2 of the 4 loo lights had been left on too!

I'm trying to find more about something my last employer was investigating - apparently there's an occupancy system which is based on you using a PC. I.e. if it detects you are at your workstation (and presumably typing and/or sending network traffic) then your bank will be lit up. haven't found it yet.

Simon

I would not go with any form of dimming , the colour of the light changes. Corridor and toilet lights should be on a PIR,so they switch on when required with a photo cell. This is a cheap mod. and actually makes life easier for those like me who used to be the only person (except for security) in an office block that has 200 + desks and many other areas, for manufacturing/drawing/wiring/software developement. etc. Walking down a 100yard corridor , even if its dead straight lit only by moonlight is very spooky!
Depending on their work, the actual illumination of any given work area is a very person sort of thing, I think the cheapest option is to go with desk lights with a CFl bulb, or two or what ever the desk user needs, BUT arrange them to have a 1hr timer that dims them to off over say 2 minutes. So the user will have to switch them on every hour, this takes care of personal preference, hours of working, time of year. . .
There could be some legal hassle about relative lighting levels, as the factory acts were written before timers, PIRs, light level sensors etc.
P.S. While you onto this sort of thing - How many PCs are left on, with just their screens dimmed?
Frank

<blockquote><cite>Posted By: James Norton</cite>I've often thought this could work in a domestic situation. Occupancy sensor could turn of lights a couple of minutes after the room is empty, with the sockets turned off after more than 30mins or so, you could also have a kill switch near the door so you can just knock out the room in one go as you leave, no standby devices + and very handy if you want to leave dramatically in the middle of an argument! Some sockets would be on an 'essentials' circuit that's unaffected. Perhaps if you wanted to get really swish a control interface a bit like the power settings on a windows PC and the sockets turn off one at a time and the lights dim off (where the LED or dimable CFL naturally).

J</blockquote>

The application works better for industrial situations, but as a lot of residential properties have cats and dogs, I think theyd be setting the things off at all hours.