Not so light work: navigating new office needs.

Jonathan Rush

Jonathan Rush, Director

An update to the Interior Workplace British Standard.

The workplace seems to be the focus of a great deal of attention when it comes to lighting.

Not only does the industry have to deal with new working from home or hybrid working practices but it also has to consider the competing forces of Net Zero Carbon and wellbeing.

In this current state of flux, it is quite an interesting time to update the British Standard for Indoor Workplaces (BS12464-1 2021) and it is fair to say that a lot has changed since its last release 10 years ago.

In 2011, when the last publication was issued, the industry was just going through another revolution – the introduction of a useable white LED. Since then, the light-emitting diode has redefined the industry, replaced all previous light sources except, perhaps, the candle and temporarily paused the lighting energy conversation by being significantly more efficient than its predecessors.

So how does the new standard meet the needs of lighting now?

In truth, it is somewhat contradictory on a few things and, as such, this has caused a stir in the industry – at least among those who see the need to challenge norms for the sake of our people and planet.

There are a few positives

The standard further enforces the importance of focusing on task illumination and maintains the importance of breaking down space into task, immediate surround, and background levels. This is important because if we are to meet the carbon reduction targets needed to meet our commitments to the planet then we need to focus lighting and lighting energy to the area that it is needed.

The new edition is more human-centric than ever. It includes a full annex on meeting the visual and non-visual needs of people within the built environment – those associated with good health and wellbeing – which discusses all things from the best finishes to use to create a comfortable environment, to the use of light spectrum to support a healthy circadian rhythm. There are also several suggested new qualitative metrics which include Chris Cuttle’s much debated ‘mean room surface luminous exitance’ method and a very welcome reminder of LENI – the Lighting Energy Numeric Indicator.

The most notable addition is that the update asks the designer to consider the age of the user as the needs of an older eye may be very different to those of a younger person. This is a welcome step and one that puts the human user and their needs in the centre of the design process.

There are some negatives

Disappointingly there is only intermittent reference to daylight and nothing which specifically sets targets for daylight, which feels like a missed opportunity. The authors will argue that there are plenty of references to the positives of daylight but by effectively separating daylight from artificial light they have lost the energy saving and wellbeing benefits of treating interiors as the 24-hour spaces that they are.

The main concern is the addition of ‘context modifiers’ (see below) for increasing interior lighting level (lux).

The designer should assess if their space meets any of the above statements and increase the designed illuminance levels by one or two steps depending on the number of the above criteria met. So, if the task is undertaken for a long time, the area has low daylight provision and errors are costly to rectify, you would need to increase from 300 lux to 750 lux, or 500 lux to 1000 lux – depending on the base illuminance level selected.

The problem is that the statements are somewhat arbitrary and if someone is relatively inexperienced or risk averse, they could translate this into greatly increased design illuminance levels and double the energy of a standard office.

If one considers the design energy density targets needed to meet Net Zero Carbon, we need to consider reducing blanket light levels in workplaces. Focussing on task with localised lighting is the solution but this can easily be misunderstood.

The inconvenient truth

The problem is that if we are to meet new recommendations for m-EDI , we may have to look at increasing vertical illuminance levels at the eye if daylight is not available. And if daylight is available, we may need to augment vertical illuminance with artificial light.

If the user is older or has less visual capacity – quite probable in an aging population – we may need more illumination. And yet, at the same time, we need to reduce energy to meet our carbon reduction needs. It is quite the challenge.

The answer lies in creating an illuminated environment that combines daylight and artificial light in a symbiotic relationship.  As daylight fades or as we move into the building, task or localised lighting provides the illumination we need and to our preferred levels. The rest of the space is background lighting with a focus on walls and ceilings to create a brighter appearance and when spaces are not being used, lighting is dimmed or switched off.

But the above requires knowledge, experience, and creativity. The problem with the new standard is that, without critical analysis and care, it effectively increases illumination levels and that is not compatible with carbon reduction targets.

Complex challenges can be solved by good design and creative thinking, but this takes time and effort. At Hoare Lea we do this all the time, but many do not and most lighting installed in the UK is done so without the input of a trained or experienced lighting professional. We must hope for our climate’s sake that people do not find easy answers within the new standard.