Changing daylight

Architect Christopher Sykes examines how Structura engineers and constructs glass and translucent solutions for maximising the benefits of daylighting

Daylighting through the creative use of wall or roof glazing radically changes building envelope design and the ambience of interiors. It positively influences people, affects how they behave in their environment, changes their circadian rhythm and improves their well-being. In schools, for example, it is proved to have had an extraordinary calming effect and marked influence on pupil behaviour and learning.

Interestingly, daylight was ‘rediscovered’ by designers in the early part of the last century and this has resulted in glazing now being an essential component of contemporary architecture. This is in spite of Part L which, taken to extremes, means that no daylight at all should penetrate the building envelope. In other words, simply introducing conventional glass can create problems.

While keeping translucent surfaces clean is one problem, the most critical are solar control and energy efficiency. However, things have changed rapidly both in the way the daylight itself is distributed internally and how its performance and effect have been tamed through the use of translucent materials. The glazing industry has come up with a neat trick or two to save the day.

Insulating daylight
In the building industry, it is unusual to enjoy new technology which totally changes design and construction. This is why aerogel insulated glazing is having such a global impact. Aerogel, the world’s best and lightest insulating solid, is now widely used by many manufacturers within different translucent cladding and roof lighting systems to increase the U-value of the glazing. Sometimes called frozen smoke, hydrophobic aerogel is produced as particles, each of which consists of up to 95 per cent air, contained in a structure with pore sizes less than the mean free path of air molecules. This severely inhibits heat transfer through the glass or panel.

The reason this new insulation technology is so important is because architects and energy-conscious designers can now maximise large areas of daylighting while reducing energy loss and minimising solar glare. Importantly, it means that well insulated daylighting will reduce energy consumption of heating, air conditioning and artificial lighting. It means that roof lights can be more energy efficient than their predecessors. Also, when aerogel is introduced inside the panels of translucent cladding and roofing systems a U-value of up to 0.28 W/m2K is possible. This is as energy efficient as a solid wall.

Diffusing daylight
As we know, there are many problems with using large areas of conventional glass – glare, overheating, insulation and energy loss to name a few. This is why many architects have now adopted an innovative system which diffuses daylight and provides a different high performance solution. Not only does it reduce energy consumption, heating and air conditioning but carbon emissions are also reduced. In other words, over the building’s life cycle, the capital costs are offset by substantial savings in energy and the quantifiable improvements for occupants in personal wellbeing and performance.

This change is the development of translucent building systems in polycarbonate and fiberglass, which alter the impacting daylight and change it into what is often called ‘museum-quality’ light. This is then diffused evenly across the interior to create a quite different and extremely attractive interior ambience.

The big difference to conventional glazing is that hot spots, together with glare and shadows, are eliminated and there is no need for internal blinds and curtains. Running costs are reduced because of the superior insulation together with less reliance on artificial lighting. Designers of sports and leisure facilities have been quick to recognise that this creates ideal playing conditions. It means that the traditional ‘black box’, windowless sports halls of yesterday have been transformed. It means that swimming pools too have become safer because glare on the water no longer inhibits the ability of life-guards to see swimmers below the water surface.

The lightness of the diffused panels means erection is less costly and, even with a steel substructure, far less cumbersome than glass. The panels have inherent rigidity and impact resistance, are largely self-cleaning and, because dirt is less obvious than on glass, frequency of maintenance is reduced.

Mixing daylight
All this new technology dramatically widens the palette of materials available for designers. It gives them the ability to change easily the ambience and performance of different rooms by mixing traditional clear glazing with enhanced solar protection with diffused lighting through translucent panels. It gives them control over the insulating U-value performance as well as aesthetics, life cycle performance and the all-important running costs.

This is particularly beneficial with the current growth in refurbishment of older properties, when many existing curtain walls and roof lights are having to be replaced and upgraded with a blend of architectural glazing and translucent building materials.