Feature, Lighting Controls, Office

How to design lighting to the WELL standard

The lighting requirements of the WELL Building Standard aim to minimise disruption to the body’s circadian system, support good sleep quality, enhance productivity and provide visual comfort.

IT MAY be product of an independent, non-government organisation, but the WELL Building Standard is rapidly gaining traction as current guidance fails to keep up with fashions in workplace wellbeing and productivity.

Developers love the on-trend endorsement of their properties and see it as added value for their tenants, so expect lighting specs to increasingly demand compliance.

But how DO you design the lighting to comply? Here Building Research Establishment lighting expert Cosmin Ticleanu explains all.

 

The WELL Building Standard is the first standard to focus exclusively on the health and wellbeing of building occupants, aiming to improve their nutrition, fitness, mood, sleep, comfort and performance. WELL addresses seven wellness concepts: air, water, nourishment, light, fitness, comfort and mind.

The light concept aims to minimise disruption to the body’s circadian system, support good sleep quality, enhance productivity and provide appropriate visual comfort. It consists of 11 features, summarised in this diagram:

 

The preconditions, mandatory for all levels of certification, are shown in dark blue circles while the light blue circles indicate optimisations, which attract optional credits that contribute to the total WELL score.

A number of WELL ‘features’ are similar to those in existing lighting standards such as BS EN 12464-1:2011, CIBSE Lighting Guide 7 and SLL Code for Lighting. This is the case for:

  • The 62-storey 22 Bishopsgate skyscraper planned for the City of London will be the largest property in the UK to comply with the WELL Building Standard 
    Feature 53, which gives lighting requirements for basic visual performance, including minimum average illuminance on the horizontal working plane, zoning of lighting in control groups, and balancing of luminance distribution within a room and between adjacent spaces.
  • Feature 55, which sets criteria for reducing glare from electric lighting by limiting lamp and luminaire luminances and imposing shielding angles for lamps of certain luminances.
  • Feature 57, which provides specific recommendations for minimising glare and visual discomfort for the use of computer screens.
  • Feature 58, requiring lighting with a general colour rendering index of at least 80.
  • Feature 59, which sets requirements for minimum light reflectance values for room surfaces.

Feature 58 also recommends a specific minimum colour rendering for red (the R9 element) of at least 50.

This goes well beyond current standards, and lighting manufacturers may not always report values of specific colour rendering indices, including R9, for their products. The number of light sources (both LED and non-LED) having a R9 value of at least 50 is limited at the current time.

 

 

Feature 54 promotes luminous environments that minimise disruption to the human circadian system. It introduces an alternative metric – the Equivalent Melanopic Lux (EML) – weighted to the spectral response of the cells in the eye that help control the body’s daily rhythms (see box out).

Standard recommendations include at least 200 EML – which may incorporate daylight – measured vertically at 1.2m above floor level at 75 per cent of more of workplaces for at least the hours between 9am and 1pm every day of the year. Alternatively, electric lighting alone should provide at least 150 EML.

The diagram below shows the equivalent visual lux levels for typical light sources and colour temperatures.

These are vertical illuminances; horizontal illuminances may typically be double these values.

These values may be very difficult or even impossible to achieve in most internal spaces using common artificial lighting practice. Lighting standards and codes generally recommend lower values of vertical illuminance to see visual tasks and avoid glare.

The adjusted illuminance levels shown in the diagram are significantly higher and may be difficult to achieve from electric lighting alone. On the other hand, lower EML values from electric lighting would be beneficial in the evening and at night to reduce unwanted health effects linked to melatonin suppression from bright light at the wrong time. The WELL standard does not explicitly recommend this, a potential weakness.

The dimming of electric lighting in response to daylight and in unoccupied areas is promoted by Feature 60. The Building Regulations Part L non-domestic guide already recommends that new lighting controls should follow the guidance in BRE Digest 498 ‘Selecting lighting controls’, which aims to provide energy savings while maintaining occupant satisfaction and comfort.

The other features (56, 61, 62 and 63) deal with solar shading and adequate levels of natural light within buildings. Requirements include controlled shading and glazing with variable transmission properties, minimum distances from windows to regularly occupied spaces, maximum annual sunlight exposure, and design parameters for windows to optimise daylight and minimise glare and heat gains. One of these parameters is minimum spatial daylight autonomy, a measure of the amount of daylight exceeded for a given proportion of the year.

Overall, WELL takes forward the design of buildings and interiors by giving tangible advice and a rating system for measuring and verifying building design and performance against health and wellbeing targets. However, whilst some features in the standard are easy to evaluate, others such as, for example, circadian lighting require more complex testing and/or modelling protocols. It can be difficult for the lighting designer to demonstrate whether they will be achieved in practice.

 

 

  • Cosmin Ticleanu is principal lighting consultant at the Building Research Establishment in the UK. Ticleanu is an expert in daylight and electric lighting and a WELL Accredited Professional, and provides consultancy and research services to government, local authorities and private sector clients into all aspects of electric lighting and daylighting.

 

 

 

 

  • Human-centric lighting will be explored in the Workplace and Wellbeing Conference at LuxLive 2018, Europe’s largest annual lighting event taking place on 14th & 15th November at the ExCeL London. Featuring eight conference tracks and over 100 expert industry speakers. Entry is FREE – simply register to attend HERE