There is a growing reliance among designers and developers to employ uniform planning guidelines regarding the depth and space of commercial office buildings. Such guidelines are used globally and ignore vagaries of facades that filter the amount of available light into the workplace. What may be appropriate for an office building in London does not suit the design of buildings in Sydney or Singapore.
Frequently the property industry applies an abstract set of criteria regardless of façade design, ceiling height, regional variances in the brightness of the sky or orientation. Such criteria are often employed by tenants (and their advisors) and have become widely accepted in the marketplace in the absence of a more considered approach. Globally uniform criteria, which disregard these broader influencing factors of daylight, become unreliable when assessing the quality of space in a workplace.
A diverse, but highly interrelated set of building elements influence occupational performance in the workplace. Four factors should be considered in relation to the depth of floor space when designing the workplace:
- The skin of the building which filters light into the space
- The height of the space to allow light penetration
- The orientation of the workplace relative to the sun
- The region or city that the building is located in and its associated cloud formations and effect on daylight penetration into buildings.
Investigating daylight and the workplace
Given that there is no reliable data upon which to assess the impact of daylight on the workplace, Woods Bagot recently initiated a study in collaboration with Arup engineers. The study was conducted over a six month period and investigated the effect of daylight on commercial office buildings around the world.
The study utilised a lighting simulation program based upon one generic floorplate with six different façade types. These façade configurations were tested over four geographical locations that approximate the global range of varying climate and lighting conditions.
Location
To provide a global assessment tool, it was necessary to identify key locations representative of the various generic global climates in which commercial office buildings are being designed. Our team selected four locations from different climate zones that vary in terms of their climate and sky type. London, Dubai, Singapore and Sydney were chosen as representative of most global locations relevant to the study.
We collected weather data for each location over a typical 12-month period, in order to determine the sky type, climate conditions and cloud distribution. Analysing each location we were able to determine an annual sky condition that would approximate daylight intensity penetrating the building envelope. Skies were classified into three categories that enable a sufficiently accurate representation of the daylight distribution impact for each location.
Once the sky conditions were established, an Annual Average Sky Model was created for each of the locations and further refined to assess conditions during normal working hours (eight am to six pm).
Floorplate model
Our simulation model is based on a simple 50m x 50m square building with a core of 10m x 10m, which allows for 20m depth of space for each façade orientation. This test model provides a generic floorplate from which variances in design can be extrapolated. Computer simulations were then run to identify the levels of excessive brightness, not enough light and useful daylight. The Useful Daylight Illuminance (UDI) method developed by Nabil and Mardaljevic was used to assess the illuminance of the floorplates. A UDI range of 250-2000 lux was selected, and divided into three zones, too bright (over 2000 lux), useful (250-2000 lux), and too dark (under 250 lux).
Façade types
As the type façade will affect the amount and quality of the light entering the workplace, we examined six of the most commonly used façade types in contemporary buildings. These six facades were chosen based on three variables:
- Ceiling (and window) height (2.7m and 3.2m)
- Shading shelf of 500mm to reduce direct sunlight glare
- Light redirecting panel located above the shading shelf to minimise indirect sunlight glare
Clear glass was employed in the façade type tests as this was considered to be the best base condition from which to asses facades of varying visible light transmission. The façade types were then tested across the four key geographical locations. A comparative daylight penetration matrix was then compiled. From the matrix, it was then possible to calculate the maximum depth of space for each façade type to receive useful daylight.
Findings
Daylight penetration varies significantly in each of the different locations. Key insights from this study are:
Floorplate depth: The optimum floorplate depth obviously varies from one city to another. Moreover, the usable floorplate depth is not uniform from one aspect to another.
For example in Sydney, the usable floorplate depth is deeper when orientation to the east and west (due to low angle incident light), rather than to the north and south. At the same time it’s important to note that those insights need to be balanced with the constraints imposed by the sun glare and solar radiation which is predominant in east and west orientations.
Ceiling height: Adjusting the ceiling height offers significant improvement to use of daylight levels by ensuring useful daylight penetrates as deeply as possible into the floorplate.
Shading shelf: Horizontal shading provided some improvement in optimising useful daylight levels along the façade in Dubai but had little or no improvement in locations characterised by diffuse sky such as Singapore and London. Its application is more useful in blocking direct sun and dealing with glare at the perimeter zones in climate types where direct light is predominant, such as Dubai and Sydney.
Light redirecting panel: Light redirecting panels have the capacity to improve useful daylight by reducing excessive daylight and glare at the perimeter zones and deflecting daylight into the deep areas of the floorplate. They provide an improvement in daylight use for all sky conditions but mainly in clear skies. It is possible to increase the UDI depth by 3.0m in clear sky locations (such as Dubai); and 1.0 to 1.5m in locations characterised by overcast skies (such as Singapore). Light redirecting panels have been shown to be most useful for east and west orientation.
Using space planning based models for determining depth of space is clearly an over-simplified approach which, if applied globally, leads to building that are suitable for perhaps London and Singapore, but certainly not for Sydney or Dubai.
Determining ideal floorplate configurations
While daylight illuminance is a powerful tool, there are other factors that need to be considered — view, glare visual contrast and ventilation, and their relationship to specific locations. The new guidelines used for the design of more sophisticated buildings are taking into account the following factors:
- Direct and indirect glare: The amount of glare, which varies enormously depending on the location — determines the way in which a floorplate can be used.
- View expectation: There is great deal still to be utilised for the psychology of view expectations and the cultural bias that aligns with the degree of urbanisation and quality of exterior landscape. Having access to a view allows people to feel connected to the outside world and there are enormous differences to be felt depending on the location. For example, a view in Dubai is often not considered as important as it is in a workplace fronting Sydney Harbour..
- Contrast pattern recognition: The human sensory system welcomes a degree of variety in lighting levels depending on the task it is engaged in. This is known as ‘sensory variability’ (Heerwagen, 1998) and the manner in which a workplace is to be used determines whether high or low stimulation is preferred. Detailed study to provide brightness contrast control guidelines to increase performance and decrease physiological fatigue in the workplace is necessary..
- Fresh air volumes: Increasing fresh air volume affects performance and careful research is required to empirically assess the correlation of fresh air volumes within the workplace with rates of absenteeism..
The benefits of research
From this research we know that daylight and its usage is a major factor in creating a better workplace. Furthermore, the locations of an office building, its solar orientation and the design of the skin of the building that filters light into a workplace, are fundamental to assessing quality of work environments and optimum depths of space.
The property industry now has a more comprehensive methods for assessing floorplates and designing high performance buildings. It is clear from this study, that we can longer assume that the design for an effective work environment in London will be the same as that required in Sydney or Singapore.
By designing a workplace that is intrinsically linked to its location and the enclosing building fabric, the industry can now deliver more comfortable environments which in turn will improve asset value and people performance. In addition, real economies can be realised by employing these findings to drive efficiencies of energy usage by optimizing building operation and minimising the use of artificial light – a more sustainable model.
This article is an edited extract of original research appearing in Public #3 Work Life, published by Woods Bagot.
Edited by:
James Calder, Director of Woods Bagot
Researched and Written by:
Earle Arney, Director of Workplace Architecture, Woods Bagot
Haico Schepers, Senior Associate – Leader Sustainable Technologies Group, Arup
Alex Rosenthal, Building Physicist – Sustainable Technologies Group, Arup
