uPVC Windows Alliance
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Developing affordable Passive Houses in Australia
A new house in a Melbourne suburban street has demonstrated that affordable Passive House construction looks within reach in Australia.
Until now passive houses were priced well beyond the means of ordinary Australians, and scared off both builders and home buyers.
But retirees Sue and Peter, builder RMH homes, passive house certifier Grun Consulting, and uPVC windows supplier VUE Windows have produced an elegant, spacious home that looks like any normal new build. Unlike those normal new builds, however, the home will produce stellar results in terms of thermal comfort and energy efficiency. In doing so, they have opened the door to more affordable, comfortable, high performing homes in Australia.
Orientation is obviously a major design consideration. Allied to this is the placement, size and type of windows. Use of high performance windows - low emissivity, double or triple glazed windows with non-metal or thermally broken frames - is essential. We think about insulating our walls; we should do the same with our windows.
Sue’s house features an expansive wall consisting of 32.45 square metres of uPVC double glazed windows and doors across the north-facing living and kitchen areas, including openable fanlight windows at ceiling height for purging hot summer air.
The argon filled double glazed uPVC windows achieve excellent insulation value of Uw 1.37 and a solar heat gain co-efficiency (SHGC) of 0.58, allowing winter sunshine to penetrate but not too much solar radiation in summer.
According to VUE Windows, in a normal house, such a large wall of glass with only six-millimetre single pane glass would result in a poor insulation value of Ug 5.8 and high SHGC 0.82, making the indoors uncomfortably hot in summer and cold in winter, or excessively expensive to heat and cool. These figures are for the glass alone; metal non-thermally broken frames are likely to increase (that is, worsen) the window U values as they conduct the heat from one side to the other.
The floor plan is shaped like a big "U" and allows natural light into each room – carefully – with appropriate placement of windows around a courtyard with good eaves and shading. The total budget for windows and external doors was a little over $50,000. Although this constituted about 10 per cent of the budget, these were an integral design element to the house and will remain for a large part of the building’s life. Timber windows were found to be more expensive and require more maintenance than uPVC, which Sue and Peter were keen to avoid as busy retirees.