A room with a view

A room with a view is even more spectacular the higher up you are. Deborah Singerman reports on designing windows for high-rise developments.

High-rise apartments that demand attention include the Gold Coast’s 80-storey Q1, Sydney’s 56-storey Lumière resi dential tower and Melbourne’s 300m, 92-storey Eureka Tower, which has 52,000 sqm of windows, gold infused glass on the top floors and flexing of up to 600 mm in high winds. Surfers Paradise is also to have 77 levels of apartments called Soul in a couple of years and Hyde, a 40-storey block overlooking the park, is finalising construction as the “only new north facing apartment development in the Sydney CBD”.

For people living at this altitude, windows must assist in giving the best possible outlook. “Views tend to drive our client’s primary inter ests,” says Ken McBryde, principal at Innovarchi. “However, we try to balance a series of other concerns. These include the experience of users in the building (light and shade moving through the spaces), how the building comes to ground, its impact on the cityscape and, of course, minimising the environmental footprint.”

The firm was specialist design architect for the podium at Q1 and is now likewise for the tower and podium of Q1’s sister tower in Dubai, the 80-storey, 284m D1, which is currently under construction. From concept to scheme design, McBryde says Innovarchi refines the brief through increasingly detailed iterations of the client’s requirements, alongside highly qualified consultants for high-rise developments, first inviting façade engineers to the team.

“There is rarely a calm day when you are 40-storeys or higher in the air,” McBryde says. “Façades of tall buildings experience stronger winds near the corners due to the turbu lence created by the winds passing around their edges. That’s one of the functions of the fins on the east and west façades of Aurora Place [for which Innovarchi was the local representative architect]. They protect the opening windows of the wintergar dens by moving that turbulence further away from the windows in the north and south façades.

“When someone opens a window a sudden intrusion of either positive or negative wind pressure can catch them by surprise, so the window type needs to open little by little and not be unre strained. Aurora Place uses very power ful motors to pull the wintergarden lou vres open and shut, and we have weather stations on the building which prevent windows from opening in high winds.”

In Dubai, fine desert sands carried by the winds meant that higher sills are also required when opening onto a balcony.

Windows need a higher performance and stronger, stiffer products to meet these high wind loads and generally higher water penetration requirements, Allan Hickey says, general manager at G. James Glass and Aluminium. “We do a site specific wind tunnel test and oper ate to very defined wind environmental effects. The test is done to determine the loads. After that we typically design the product to meet those loads, as well as the various rules, specifications and Building Code of Australia (BCA) stan dards. We then do further mock-up tests and check the design and waterproofing and so on,” he says.

“Every job is different. They are driven by aesthetics and location and are quite different from normal residential housing where you have a standard product and standard size. It’s all custom-made in size and custom in design. The differ ence, say, between 30-storeys and 70- storeys is a matter of scale and having to go through it in more detail.

Lumière was a total custom design — every extrusion was specifically made for the job. “We did a sliding window that went across between the curtain wall panels to get ventilation and a very large view. It was one piece of glass 2.2m wide (an average width in a building is 900 mm) and 900 mm high. This large win dow took many months. [The architects] Foster + Partners knew exactly what they wanted and documented it very well,” Hickey says.

Tracey Gramlick, executive director of the Australian Window Association (AWA), warns of the importance of counting windows for Class 2 buildings, which includes apartments, as windows for residential applications and not as windows for housing. This means that after having a nominated deflection test at a specified design wind pressure, “no structural members in a completely assembled and glazed window shall deflect by an amount greater than span per 180 when tested at the serviceability design wind pressure,” she says.

“The windows also should not collapse when subjected to the ultimate strength test nominated (wind pressure design for both determined in accordance with AS/NZS 1170.2:2002 Structural design actions, Part 2: Wind actions). All local pressure factors and internal pressure coefficients relevant to the location of the window on the building need to be considered. Specifically, the test pressure for water penetration is calculated as 30 per cent of the positive serviceability limit state design wind pressure, but not less than 150 Pascals.”

She reiterates the need for stiff prod ucts with significantly better water resist ance capabilities. Designers can also nominate higher standards than the minimum for weather tightness and structural requirements (AS 4420 — 1996 Windows — Method of Test) if project specific circumstances warrant it, says Meinhardt’s façade technology general manager Tony Alvaro and Building Science Group associate, Michael Shaw.

Window manufacturers and consult ants alike believe that advances in glass technology, with the rapidly improving performance of windows, cannot be underestimated for the control of acoustics, energy efficiency and occu pant comfort levels in high-rise build ings. Common glass types are insulated glass units, low-E glass and solar control products — or a combination of all three.

“With an increase in density, particularly along major rail or road networks, cou pled with a trend for larger expansions of glass to increase connectivity with exter nal elements, there has been a paradigm shift with glass in residential building designs,” says Paul Cocker, Viridian’s commercial marketing manager. “Glass made in the 1960s next to today's mod ern performance glass is like comparing a tape recorder to an MP3 player.”

Acoustic issues these days, for instance, can be addressed by laminated glass, such as the Viridian VLam Hush, which was used for a 15-floor adaptive reuse apartment block in Sydney’s Milsons Point. This has an acoustic interlayer to dampen noise at both low and high frequency, reducing sound.

“Unlike single level buildings, which can be designed with reliance on orienta tion, this is not an option for high- rise buildings which often feature glass façades on every aspect,” Cocker says. “In residential buildings especially, you need a balance to maximise the amount of light and, depending on the climate, reduce the solar heat gain as much as you can, therefore minimising lighting, heating and cooling costs. The lower the solar heat gain coefficient the less heat that enters. Energy efficient windows can improve thermal comfort by making a building up to 5°C warmer in winter and up to 10°C cooler in summer.”

More stringent energy efficiency provi sions are to be introduced in the BCA 2010, and while these are expected to have a greater impact on the use of per formance glass in commercial buildings, apartment buildings are likely to be scru tinised further as well.

Australian designers, developers and real estate professionals are often reluc tant to reduce window areas on build ings, yet this is an energy efficient strate gy, say Meinhardt’s Alvaro and Shaw. To allow the continued use of external glazed areas, they expect to see more external shading devices, double glazing (especially with inert gases such as argon in the cavity), low-emissivity coatings and tinted glazing with low solar heat gain properties. External blinds are rare because they have to be maintained, however, shaded fixed overhangs, louvres and perforated metal screens are more common due to their durability.

There is also likely to be a greater demand for low conductivity frames to reduce overall window heat conduction. Overall, Cocker and others predict that double glazing is likely to become more popular with legislation, market aware ness and consumer demand for better performance.