Most of us have been raised with the idea that the single aim for office lighting design is to reduce energy costs. Technological advances (the LED) and good product design (photometric performance) have helped with that goal. But there’s another metric in town, suggesting that W/m2 isn’t the whole story. In fact, it’s a very small part of it.
The alliterative 3:30:300 (poetry always has its place) was originally conceived by Facilities Managers in the USA as a way of describing the essential costs that companies incur in running the business. Its easier, though less expressive, to put this into percentage terms, so let’s do that.
- 3: or 1%: the cost of energy / utilities.
- 30: or 9%: the cost of the premises, rents and the like.
- 300: or 90%: the cost of the staff.
Until recently, traditional silo thinking has meant that the lighting industry as a whole hasn’t given much thought to anything other than the W/m2 metric. And we’ve done very well at that, as I say above. But it doesn’t take a maths degree to understand that the real effect on business cost isn’t built around the efficacy of a luminaire or light source. If good employment practice (whatever that means) can reduce staffing costs by, say 1%, then the entire cost of the utilities is covered. What might this mean in practice, and what does it mean for the relevance of energy saving?
Working the 1%
We know this one. The aim is to design an office lighting scheme that minimises the installed energy of the installation. The problem we have is that it’s a reductive idea, driven simply by having as few efficient luminaires as possible. It works if you’re light planning is built around open plan spaces and large floorplates – an office model that is now considered outmoded.
But let’s not forget that there is a global picture here. Energy costs may only represent 1% of business costs, but we have a planet that’s getting dangerously out of control vis-a-vis our survival. Whatever happens next, we have to remember that.
Working the 9%
We haven’t really been here before. All we do is light the spaces that are put in front of us; what those spaces are for is someone else’s problem. Except that it is becoming our problem.
The current model for office space is for Facilities Management to consider physical space as being far more flexible than we’re used to. Rooms that stand empty, perhaps because the occupants are out at meetings, are still costing money. Better to create multi-tasking spaces that can be used all the time – just don’t get settled! It’s a method that is reducing the total amount of space that companies need. Consequently, the lighting of these spaces needs to reflect that flexibility.
Working the 90%
This is about reducing staff absenteeism, sickness, and general employee churn. The theory goes that a happy staff is a committed staff. Productivity is better, errors are reduced and quality is higher. We are beginning to understand about this through the work that’s being done on biodynamic lighting. The human body has a physiological response to the lit environment and a lot of work is going on currently to understand that relationship better. And there is a hardening towards the idea that circadian lighting needs to provide far higher levels of illumination in the early morning working hours. That light has to come from somewhere (and daylight exposure needs to be a different article altogether!).
But there’s another aspect to improving the working environment for staff. The traditional ranks of desks that disappear down the length of a building are being replaced by more relaxed working arrangements. Offices are looking more like hotel lobbies than the slave galleys that many of us grew up with. Illumination levels are actually going down, rather than up.
The criteria that much of office lighting standards was based upon have also changed; we’re all using illuminated screens and paper is seen less and less. It doesn’t mean that we don’t need those lighting standards, we just need to pay more attention to SLL LG7 to understand what office lighting is meant to be these days.
The conundrum
There is no doubt that installed lighting energy costs will increase if the 9% and 90% metrics are to be pursued. Chasing the 1% dream has stripped out any wriggle room for designers, so we now need to look in a different direction. Business managers may want to be avoid being seen as profligate with their energy use, but they also need to run a successful enterprise, so energy costs need to be off-set against work aesthetics. Fortunately, we do have an answer.
The solution
Somewhere in the past decade or so, energy efficiency reporting made a subtle shift. Again, back in the day, we totted up the total number of fixtures, multiplied that by the wattage of the fixtures and came out with a number. Divide that by the square metreage of the building and that was the hallowed single metric of W/m2.
But then, those numbers started to tumble considerably – unfeasibly, even. As we all know, what happened was that time and usage were brought into the equation. Rather than basing ‘wattage’ on the installed load, it was measured on the amount of power in use. So a 20 W/m2 installed scheme that was only in use for half of the time could be reported as a 10 W/m2 scheme. Simple.
Its all down to controls.
When the only control was a bank of switches by the door, it made sense to use installed figures. After all, there was no one in control and the horror images of entire buildings glowing into the midnight sky showed that it reflected what was actually going on.
By introducing automated control strategies, and especially by engaging with smart technologies, the energy usage of a building now accurately describes the way that a building is used. When a meeting room is empty, the lights are off; when there is available daylight, then the artificial lighting adjusts to maintain planned illuminance levels; presence detectors control the lighting of circulation spaces.
The conundrum stands, but only because there are to many instances when the appropriate questions are not being asked. The solution is already with us, we just need to engage with it.