This CPD, sponsored by VELUX Commercial, explains the considerations to be weighed when specifying structural glazing for commercial buildings, the opportunities it creates for designers and the benefits for employers and their staff
We all know the advantages of natural daylight, and this extends to places of work. Clearly there is a need for electricity to illuminate commercial buildings, but if a space is able to utilise specialist glazing as part of its fabric then its occupants stand to gain in several key areas.
This CPD will outline the value and importance of structural glazing in building design and examine how it can aid productivity, health and wellbeing.
While we do not yet understand how recent events will influence our day-to-day working culture in the long term, the coronavirus’ effects are unlikely to have an impact on building design and construction. The design and manufacture of new commercial buildings or the refurbishment of existing spaces will still require careful consideration of lighting needs dependent upon the use of the space.
We may never manage to completely get rid of the need for artificial energy to illuminate, heat or cool our indoor spaces. Either way, designing daylight into the makeup of our buildings will always be regarded as an essential element of well-designed commercial buildings.
Thanks to its flexibility, structural glazing offers a solution that can allow an architect to design with freedom while supporting a commercial building’s energy and lighting strategy, plus its overall performance.
Light and its role in architecture
Industry uses the measurement of lux to determine the illuminative strength of a particular light source. Examining these measures for daylight and artificial light illumination helps to demonstrate the great difference between the two. Direct sunlight delivers approximately 100,000 lux and daylight varies from 25,000 lux on a sunny day to 2,000 lux on an overcast day. Artificial light, meanwhile, typically delivers in the range of 200-300 lux, though 500-2,000 lux is easily achievable with modern lighting.
For context, areas such as hotel lobbies require a minimum of 200 lux. In offices this rises to 500 lux, while in spaces where manufacturing is undertaken or where improved visibility is needed for health and safety, 500-2,000 lux is recommended. It is clear that, no matter how advanced artificial lighting has become over time, it still cannot compete with the intensity that daylight offers.
Although some of the characteristics of daylight can be mimicked by artificial light, the visual and non-visual benefits of daylight cannot be reproduced artificially. Applying daylight-focused thinking is key to achieving truly human-focused building design.
Daylight design and the commercial sector
Most architects and designers are familiar with designing for daylight provision in commercial spaces as best practice. But improving illumination levels is just one element of the daylight design concept; the new European Standard EN 17037 broadened the scope to achieve a number of goals with regard to daylighting and occupant comfort.
EN 17037 addresses four important areas: daylight provision, access to sunlight, prevention of glare and assessment of the view from windows. The standard sets out a minimum performance level, but a medium and high level can also be targeted, although this depends on the specific requirements of a given project. This flexibility is certainly useful in commercial design. And while there are daylighting strategies and aims that will be identical across industries, there are areas that have a specific impact on certain building types.
According to a study by Romm and Browning more than two decades ago, companies occupying buildings where daylight was prioritised reported reduced absenteeism, increased productivity and fewer mistakes. Putting a healthy environment in place has a positive effect on the growth of a business. The initial investment into appropriate glazing solutions that offer improved daylighting, thermal comfort, acoustic balancing, improvement in air quality and views will see a manifold return over the lifetime of the building.
According to a study conducted by Imperial College London in 2017, addressing all these areas could bring a productivity improvement of around 5%-8% of business turnover, and upfront investment into the initial design or an upgrade of a building has a payback period of as little as two years.
Roof glazing can provide twice as much daylight as vertical glazing and is frequently specified for warehouses or airports and in buildings where optimal visibility in a non-homogeneous landscape is essential for workplace safety and workforce efficiency. Combining roof glazing with facade glazing can help to reduce glare and provide high illumination levels, so this approach is often used in sports venues and leisure facilities where excellent visibility is important for customer experience and retention.
Structural glazing – what is it?
Basically, structural glazing systems are streamlined products that are installed using a variety of methods and convey the appearance of being part of the fabric of the building. They allow commercial buildings to have windows as walls and roofs, or to have walls and roofs as windows, yet they hold structural elements together to create a strong and secure building envelope. The level of design customisation can provide the exterior of the building with a more homogeneous finish that minimises visual interruption to the facade or the roof.
Structural glazing’s flexibility is just one of its selling points. It offers an array of opportunities for designers and architects and allows for innovative architectural design. Numerous options are available which present the flexibility to specify a system that fits best with the desired design and performance.
Structural glazing – more than enhancing lighting
The advantages of structural glazing do not simply lie in maximising available daylight. A major contributing factor to the increasing use of structural glazing in modern architecture is its loadbearing capacity. It is important in the conception stage to use a holistic approach and consider structural glazing as part of the fabric of the building. With careful design, the loadbearing capacity of a system could, for instance, be used to minimise the use of steel structures that would otherwise be required to support a glazing solution.
As with standard rooflights, skylights and facade glazing, qualifying criteria must be taken into consideration, although the installation of structural glazing is not as predetermined by the opening available to the same degree. The size or span of each glazing unit can be significantly larger, depending on the rafter depth used and the fragility rating required for the design. This affords the designer a greater ability to create larger unsupported shapes with fewer sightlines and better light transmission.
The choice of glazing material will be guided by the functionality of the building and the design specification. It is important to note that various materials have different fragility classifications, and these should be strictly borne in mind. Guidelines published by National Association of Rooflight Manufacturers explain the fragility tests – CWCT TN66/67 for glass and ACR [M] 001-2019 for polycarbonate – and will determine the maximum size of the glazing pane, whether glass or polycarbonate, to support the intended roof function.
The classifications of non-fragility for roofs are as follows:
• Class 0: Rooflights are effectively walk-on solutions.
• Class 1: Rooflights allow walk-on for maintenance purposes only, with full safety kit to be worn.
• Class 2: Rooflights are not designed to be walked on, but they are able to take impact in the event of maintenance personnel falling upon them – in this case the outer toughened pane of the glazed unit may break, but the inner laminated pane is designed to prevent a fall for 30 minutes.
• Class 3: Under no circumstances should these rooflights be walked upon. These solutions should also have a barrier around them or be on an upstand sufficiently high enough to ensure they cannot be walked or fallen upon.
In the case of polycarbonate glazing: The Class B Non-Fragile to ACR[M]001:2019 Test for Non-Fragility of Large Element Roofing Assemblies should also be used.
Safety considerations should always be at the forefront of glazing specification, but this is a small price to pay for the almost endless possibilities that various glazing options can offer architects for enhancing the external visual appeal of a commercial building.
Bespoke structural glazing – the imagination knows no bounds
By using bespoke structural glazing systems, architects and designers have the opportunity to choose an ideal span, size and shape of a given opening. As regards the building envelope, the location of the opening can be flexible and glazing customised to fit with the desired surface curvature or a roof pitch. Removing the need to consider the glazing solution at the conception stage means a designer is presented with freedom to remain faithful to their original concept.
A bespoke approach to structural facade glazing changes the sheet of glazing that envelops the building to open up exciting design possibilities. Curved or radiused external glazing or even multiple curvatures can be deployed, while non-rectangular shapes and more irregular shapes can be used for multifaceted facades. The striking look this can create will add dimension to the building and can be complemented by light reflection.
The ability to use various glazing shapes expands how daylight can be used internally for asymmetrical light distribution that increases visual comfort. In roof applications, asymmetrical light can help with the transition from light to dark and softening of shadows and contributes to a better experience at a large stadium or in theatres and museums. The freedom to create non-standard shapes of unusual sizes results in glazed roofs shaped to fit the message of the design and function of the building. The far-reaching light used in atriums and central spaces or walkways of commercial spaces can create a feeling of synergy and connection between the occupants and nature.
Humans did not evolve to live indoors. Physically and psychologically we yearn to be connected to nature. This distinctive connection is shown in how our bodies and minds rely on the rhythms of the outside world, which are affected by daylight. Disconnection from outdoor space and lack of fresh air or daylight disrupts our natural cycle of sleep and wakefulness. It is possible to ignore this but not without consequences to our health and mental wellbeing. From a commercial perspective, to have a workforce lacking in motivation, struggling with productivity and frequent health-related absences is a burden both to finances and to the growth of the business.
Daylight is free energy. It makes commercial sense to build spaces where the use of daylight can improve energy usage. The investment in energy efficiency also makes a commercial building more environmentally resilient and future-proof.
The customisation levels provided by bespoke structural glazing give the designer carte blanche to achieve their vision no matter how unusual or complex it may be. The flexibility bespoke structural glazing provides means that daylight design can be included in considerations before the architectural concept is defined, giving complete freedom to create and innovate. With the right support, there are no boundaries to the imagination.