Daylight design within buildings - what should we be prioritising?

Overview
The various national lockdowns triggered by the Covid-19 pandemic have highlighted the importance and value of daylight and our access to it. With most of us now finding ourselves closer to a window, the positive impact of having a view of the sky and feeling / being closer to nature within our ‘home office’ has never been more essential. Typically, this is not so common in a traditional office/ city environment, where high-rise buildings are in close proximity to one another, with restricted views of nature and where long distance/wide angled views are not common.

Can the design guidance within BS EN 17037:2018 -Daylight in Buildings change the user experience of the office environment for the better? The end user is ultimately the one effected so are we the ones that need to shout out that this is important?

The standard encourages building designers to assess and ensure successfully daylit spaces. It also allows building designers and developers to target ambitions with respect to daylighting, as well as views, glare, and sunlight.

Daylight
Daylight is an invaluable source of illumination for all spaces with daylight openings. It is the most effective way to adequately illuminate indoor surfaces while saving energy on electrical lighting. BS EN 17037:2018 has tables that advise on target illuminance to a reference plane. This target illuminance is ranked minimum / medium / high and daylight levels are to be achieved on 95% of the reference plane for 50% of daylight hours (95/50).

To analyse the target illuminance for daylight as set out within the BS standard, we have created a rhino/grasshopper script that evaluates daylight levels on the working plane of a sample space. These are assessed against the criteria of minimum (300lux), medium (500lux) and high (750lux) and allows us to understand how the space is performing with respect to the quality of daylight.

Views
The view and specifically the quality of the view is rarely considered at a sufficiently early stage when an office is being selected or a seating plan is being formulated. A good view is more subjective than good daylight, however BS EN 17037:2018 assesses a good view on the horizontal sight angle, outside distance of the view, and the number of layers seen of the following elements (criteria = at least 75% of the utilised area):

• Sky
• Landscape (urban and/or nature)
• Ground

Additionally, a quality view can be split into a variety of things:

• The outside distance of the view
• The quality of environmental information
• The width of the view
• The size of the daylight opening

There are so many elements that contribute to a good view and users have found that many are readily available to them within their ‘home office’ set-up.

Will this be the case when moving back to the typically deeper plan office? What are they ways this can be improved?

Sunlight and glare
The recommendation is that a space should receive sunlight for a set duration of time, dependant on the degree of sunlight exposure. Three levels are proposed for this: minimum, medium, and high.

The recommendation is that the Daylight Glare Probability (DGP) should not exceed a maximum value when assessed in relation to the usage time of the space (DGPe < 5 %). Three levels are proposed for glare protection: minimum, medium, and high.

For both sunlight and glare, the metrics for each ‘level’ have not been clearly defined, making it difficult to quantify what equates to each. Further investigation is needed to fully understand how this can be effectively implemented into the design process.

Takeaways
The guidance within BS EN 17037:2018 - Daylight in Buildings sets out the parameters for daylighting, as well as views, glare, and sunlight – providing targets and criteria for building designers and developers to assess spaces.

This exercise is already being undertaken in the field of school design - the Department for Education (DfE) daylighting appendix outlines the mandatory daylighting criteria required to enable a new school to attain funding. Whilst it is not compulsory to design in this way for offices, the end user is significantly impacted by the quality of the daylight, views, glare, and sunlight within their experience zone.

We feel that the guidance needs to make its way into design team meetings and should be a key consideration of city planners when they consider the future of our cityscapes.

Can daylighting and views be at the top of the list when choosing a location for a new office?

This could mean that, as cities become more densely packed and buildings climb higher, the ‘best’ location is more rural. This ultimately needs to be weighed-up against the practicalities.

For instance, the DfE daylighting appendix outlines the mandatory daylighting criteria required to gain funding for new schools. Is it now time for mandatory daylighting criteria for all newly constructed office buildings, in view of the industry's net zero carbon targets?