The secret to low-energy office lighting? Forget about watts per square metre

If you want to come up with a successful, energy-efficient office lighting scheme, then don’t get hung up on the watts per square metre figure.

That’s the advice of Andrew Bissell, head of Cundall’s lighting division, who believes that a crude view of energy efficiency, without properly considering the influence of good design, can lead to ineffective, inefficient schemes.

‘If you start thinking about the people, start thinking about where you’re going to put the light and why, you’ll find you design better and you save energy as well,’ Bissell told Lux’s Lighting for Large Estates conference in London yesterday.

‘We are quite often challenged to just look at the numbers, just look at the W/m2,’ Bissell said. Very rarely do we get a client coming to us saying, it’s about the people who are using the space, it’s about the design. Instead we get them asking about W/m2, because there’s a number there, there’s an actual financial number that you can apply to the energy efficiency. Whereas good design, you can’t really apply a number to that. How much do you save because people feel better within a space? It’s hard to quantify that.’

Bissell recently oversaw the design of lighting at Cundall’s new Birmingham office, with a big focus on lighting for people and tasks, rather than chasing target W/m2 figures or slavishly following guidelines. This means lots of task lighting, lots of natural light, only putting light where it’s needed, and clever use of controls. The result was a scheme with an operational load of just 4W/m2.

This, he said, was an example of a project where ‘the design is better, but actually there is greater energy efficiency if you start designing for people’.

It’s usually upfront cost and payback periods that prevent this kind of thing from happening, Bissell said. ‘Certain clients have to see the three-year payback. If it’s three years and three months, they can’t take that back to their board . So what we’re seeing is, the only way to make these projects stack up is point-for-point replacements. Once you change the wiring, once you start suggesting that you should light the space differently and you apply a bit more design compared to what was there before, the projects just don’t stack up.

‘There’s a certain amount of savings to be had on a point-for-point replacement, but you can save more CO2 if you design a space properly and make changes to your lighting. But actually all that some businesses can afford is the first option.’

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