IGUs keep the views
hen there is a great view to be had, it makes sense to have a house that allows you to appreciate it. In order to meet energy building codes, it is important to consider the right combination of energy efficient glass and window frames that help insulate the home, while keeping the view.
Director Sally Bartholomeusz of Saaj Design is an accredited FirstRate energy rater. She recently designed a two-home residential project in the Melbourne suburb of Ivanhoe, which features what is believed to be the largest double-glazed window in any residential project. Constructed by Becker Building, the project on a very large site on the side of a steep hill has a spectacular view of Darebin Creek. The construction type is split-faced block work, timber lining boards made of stained plantation cedar, timber framed glass and steel detailing. The site has west-facing views, and the houses are built side by side, split along the east/ west axis and slipped past each other.
“The design and construction is similar, but each house still has a personality of its own,” says Bartholomeusz. “They appear to be single storey at the front, from the street side, but from down the hill, appear as two storeys. The landscaping involves courtyards to improve eastern light. The full landscaping will be carried out later, but the intent is for there to be thick landscaping as you enter each property.” The homes feature special attention to ventilation, including operable windows. “Each family has a pool, and the water bodies have a cooling effect, as wind moves up the site,” she adds.
Saaj Design designed the houses to have as much northern highlight window area as possible. One house has northern glazing. The other has highlight northern and north eastern glazing. There are some south-facing windows used in the southern dwelling. The primary windows face to the west, and the house features large eaves overhangs to shield the windows from the effects of the summer sun yet capture winter warmth.
The window frames are made of timber, with aluminium improved stackable sliders in some places. Timber is one of the most energy efficient window framing materials, and it adds to the energy performance of the windows in each of the two houses. The Insulated Glass Units (IGUs) offered a way to maintain large glazing areas so that the homeowners could enjoy the excellent views, without making the house a hotbox in summer and an icebox in winter.
A study by Arup Engineering found that, in an otherwise well-insulated building in summer, up to 87 per cent of solar heat gain can occur through non-energy efficient windows, while in winter up to 49 per cent of heat loss can occur through non-energy efficient windows. The architect chose effective energy saving options: IGUs and timber window frames, which help to complete the insulation envelope of a building.
In this project, the IGUs used are all Thermotech units made by Viridian (formerly Pilkington and DMS Glass) in Victoria. The Thermotech IGUs consist of two sheets of glass with a Thermo Plastic Spacer that significantly reduces heat from travelling through the unit. For added insulation, the sealed unit is filled with argon gas, which is a superior insulator than air.
Energy efficient glazing and window frames cut down heat transfer, making the house more comfortable in both winter and summer, and cutting down on energy costs. Independent research found that, due to their Thermo Plastic Spacer and argon gas fill, Thermotech IGUs are now Australia’s most energy efficient. IGUs in Australia normally have an aluminium spacer, but aluminium has a high heat transfer, and the independent research, which was commissioned by DMS Glass, and carried out by window expert Dr Peter Lyons, found that the Thermo Plastic Spacer makes the Thermotech units 12 per cent more energy efficient than aluminium spacers and air-filled units.
Builder Adam Becker of Becker Building says that there were a few testing aspects to the job from a glazing point of view. “Putting in the up-top windows, and handling the large panes posed some challenges, but Aspect Windows, the specialist window manufacturer contracted to supply the windows, were up to the challenge,” explains Becker.
Norm Brodie at Aspect Window reports that 80 per cent of the project was straightforward. However the largest double-glazed panel measuring 2,350 mm high by 3,650 mm wide and weighing in at approximately 340 kg posed some serious handling difficulties which the team at Aspect Windows overcame using a crane to lift the windows on and off the truck, along with some good old-fashioned ingenuity. “Aspect Windows has determined through prior experience that the safest way to deliver large panel windows is in factory-glazed form,” says Brodie. – Jon Hoel
23-Mar-2007