There are still very many offices illuminated with fluorescent lamps. Some even have wire-wound control gear which uses magnetic transformers. If so, it really is time to change the lighting to LEDs.
Assuming you have done this or are about to, the next step is to make friends with your national energy code. E.g. EN 12464.
Improvements in lamp and luminaire efficiency can only go so far. The real savings are made by considering the office as a whole - what work goes on, where and when it’s done.
If EN 12464 seems too technical, get a copy of professional guidance documents such as the Code for Lighting. These are really easy to read and not only help you meet the standards but also to avoid some of the pitfalls like discomfort glare or dark ceilings.
Something to watch out for is that the old fluorescent panels often had “Cat 2” low glare louvres which restricted the light above 65 degrees (from straight down). Some low quality LED panels can be glaring. Check that the panels are UGR (Unified Glare Rating) compliant for the dimensions of your particular office and the tasks that are done there. Instead of UGR, some national codes limit the intensity of the luminaires at certain angles.
Like most offices, our Design Clinic has windows and we have used daylight to save energy by switching off some of the luminaires. Of course, you do need to check that there is sufficient daylight before switching off rows of luminaires!
The office is approximately 15m x 10m with a 3.2m ceiling. We have designed to a task illuminance of 400 - 500 lux. This excludes the contribution from daylight.
Direct/Indirect solutions often give the best visual appearance. You achieve bright ceilings, high uniformity across the whole space and good vertical illumination of people’s faces.
Since a lot of the light is reflected off the ceiling, and the diffusers are low brightness ( low luminance), it is a very comfortable scheme to look at. The Brooklyn has an opal polycarbonate panel which is side-lit from the LEDs mounted in the frame which is only 22mm (7/8”) thick.
In terms of delivered lm/W, this is the most efficient luminaire. The scheme has five rows of fittings and it would be simple to switch off the first or even, second row when there was sufficient daylight.
The Brooklyn luminaires are suspended 750mm (30”) below the T-grid ceiling panels.
Tech spec A
- LuminairesBrooklyn Direct/IndirectOptical controlOpal polycarbonateArrangementFive rows of six
- Luminaire delivered lumens 4,510
- Electrical load 36W
- Pros Maybe the best appearance
This is a simple scheme using the Infinite LED recessed panel. It has a dimpled polycarbonate diffuser which is UGR <19 compliant. To save energy, you can see that we have switched off the row closest to the windows. Since there are four rows, this gives an immediate 25% reduction in energy consumption.
What you cannot see in the image is that the Infinite panel is fitted with a 5W emergency Panel Pod. This is a small (170mm dia, 6.7”) accessory that converts any Infinite panel to an emergency unit. It has a quick twist and lock fixing and locates on the back of the panel. This clever little device emits 220 lm over a 120 degree beam.
Tech spec B
- Luminairesnfinite panel plus Panel PodOptical controlDimpled polycarbonate panelArrangementFour rows of sixLuminaire delivered lumens 3,300
- Electrical load 36W
- Pros Economical
This is another Direct/Indirect scheme but this time using the Otto which is only 61mm (2.4”) wide and 100mm (4”) high. On the other hand, it is much more powerful at 84W and it emits 7,250 lm. Like the Brooklyn, we have suspended them 750mm (30”) from the ceiling. A single direction version is also available.
You can see that just three rows have been used and, again, one row is switched off due to the daylight. Obviously, this is switched on once it is dark.
Having so few fittings means that they are very inconspicuous in the space. Like most direct/indirect schemes the Otto, gives a light and airy appearance to the office.
Tech spec C
- LuminairesOtto Direct/IndirectOptical controlPrismatic up and downArrangementThree rows of fiveLuminaire delivered lumens 4,930 down, 2,320 upElectrical load 64W down, 20W up
- Pros Fewest number of luminaires