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Wednesday23 July 2014

Glaze of light

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In development for years, Serraglaze lamination may be coming into its own as a way of boosting natural daylight and cutting energy use. Roderick Bunn looks at how Hurd Rolland used it at a university science faculty

Light is the most unpredictable variable architects have to control. It changes angle, colour and shading characteristics depending on time of day, season, and the weather. Architects often struggle to design fixed elements like windows and brises soleils that can cope with these constantly changing conditions.

Motorised, solar-tracking louvres and double-skin facades can be very expensive alternatives — if they actually work — and can be a nightmare for a building’s occupants to maintain. And cheaper systems such as fixed solar shading will only work well at certain times of day.

Despite efforts by architects to maximise natural light, problems like glare on computer screens and strong contrast between well-lit and gloomy areas in a room often occur. And once a building’s occupants adopt a lights on, blinds down mentality to solve these problems, any daylighting strategy lies in tatters. What architects and facade engineers need is a way of allowing sunlight and daylight deep into a structure without these problems.

Even spread

One emerging technology offering a way out of the daylighting problem is Serraglaze, a light-bending film placed as a laminate between two sheets of glass. When used in standard glazing or projecting solar shades, Serraglaze reflects and refracts incoming sunlight, directing it deep into occupied spaces and improving the uniformity of natural light.

It consists of two very thin layers of acrylic incorporating minute, precisely shaped and positioned air pockets which bend light. The prisms or lamellae are perpendicular to the 1mm-thick sheet and act like reflecting mirrors. When struck by light beams, they act as miniature light shelves, reflecting light upwards to the ceiling and also refracting it downwards.

The effect is to redirect incoming daylight towards the ceiling, from where it bounces deeper into the room. Daylight can be distributed far more uniformly rather than concentrated at the zone nearest the window. Light hitting windows at high incidence, typically at midday in summer, is also intercepted before it causes glare to those seated nearby, and is reflected deep inside the room. The best effect is achieved with a flat, white-painted ceiling that acts as a secondary reflector. The product can also be used in canopies, vertical windows and glazed walls.

The ability of Serraglaze to prevent high-incidence sunlight from passing directly to the floor makes it a useful mechanism for reducing glare and providing some shading. The supplier, Bending Light, also believes that it treats solar radiation in much the same way as visible light, acting as a brise soleil to shade a building’s occupants from the direct heat of the sun, as well as from sunlight itself.

Little known

Serraglaze has yet to become mainstream technology, although it has been in development for years . The only major application in the UK to date has been in two buildings at Edinburgh University’s Kings Buildings Campus, designed by architect Hurd Rolland Partnership.

The practice, which has an Edinburgh office, specified Serraglaze for the Alexander Graham Bell science facility, where the client was keen to pilot advanced technology in the building — for its research and educational value. Project architect Alan Clyde used Serraglaze film between the glass of the Levolux top-light louvres in the windows of the east and west facing offices and labs. The finned louvres are designed to reflect light upward.

“We have three glazed louvres, but only the top two use Serraglaze as it does slightly restrict views out,” says Clyde. “With the white-painted ceilings, the Serraglaze increases daylight in the space by about 20% throughout.”

Based on the success of the pilot project, Hurd Rolland has used Serraglaze in the facade of the recently completed 3,000sq m William Rankine Building, built for the university’s department of civil engineering.

Clyde says the cost of Serraglaze for the university projects was not significant. “It’s not a huge cost, particularly if you are using a louvred system anyway,” he says.

Hurd Rolland’s experience of Serraglaze at Edinburgh also suggests that designers need to think through the implications before using the technology.

“The method of bonding Serraglaze between two pieces of glass means that you can see the join between the square panels, and any slight debonding that may occur between the glass and the Serraglaze,” says Clyde.

“It’s important for designers to make sure the client understands what he is getting,” he adds. “Serraglaze will have a slight impact on views outside, which is why we restricted its application to the top two louvres.

“It is also worthwhile showing a sample panel to the building’s occupants to let them know what they are going to get.”

Modeling Serraglaze

John Mardaljevic of the Institute of Energy & Sustainable Development at Leicester’s de Montfort University has run computer simulations of Serraglaze both in a standard glazing configuration and as a projecting light shelf.

Mardaljevic has discovered that vertical and projecting Serraglaze installations increase daylight at the back of a 3D-simulated office space compared with standard glazing. When high-angle direct sun was modelled, particularly for south facing glazing, vertically mounted Serraglaze reduced the level of direct sun exposure at the office front, while the degree and pattern of sun exposure was largely unchanged.

Mardaljevic’s models also show that Serraglaze can obstruct views outside, and can cause bright spots on building surfaces that would otherwise not be subject to light beams or high levels of light illuminance.

Using a projecting solar shade, research suggests that Serraglaze would not protect front-of-office space from any high-angle sunlight as light that strikes the projecting panel experiences little or no redirection.

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