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Green Smart Magazine : 2009_new
Windows and doors literally represent a major opening in the building envelope of a home, with obvious results. And with up to 40 per cent of a home's energy for cooling or heating being lost or gained through windows, improving their thermal performance is a must for reducing energy costs. Of course if you want virtually unrestricted views and natural light, with larger windows and doors, making your home energy efficient is going to be more of a challenge. Fortunately, there are a number of ways you can have the best of both worlds. Advances in glazing technology mean that great expanses of glass can be treated to allow for minimum heat transfer while preser ving those precious lifestyle choices. And where you place your windows and doors can also make a big difference. It's important to consider the effects and understand the insulating properties of glass. If you've ever sat next to a plain, standard float glass window with the hot summer sun streaming in or against the winter chill, you certainly would have felt it. This type of glass -- which is transparent and colourless -- offers little resistance to solar heat gain or loss, or to glare. An insulating glass unit (IGU) will significantly limit the transfer of heat in or out of a home, especially if combined with low-e glass. Other types of glass, e.g. toned float glass, laminated glass or toughened glass, can also make a difference to the comfort of your home. Heat can also leave or enter a home through gaps and cracks around sashes and frames. Hinged windows are thought to generally have lower air leakage than sliding windows, either horizontal or double hung. With careful attention to orientation, glazing and shading, you can have your windows and energy efficiency too. rooms with a view story > Louise Tigchelaar windows+doors glass terms explained IGUs -- two or more panels of energy- efficient toughened glass with an air space between. IGUs have a dual seal with a desiccant-filled spacer to prevent condensation inside the cavity. Low-e -- or 'low-emissivity' glass. Low-e glass has a hard durable pyrolitic coating on its internal surface and largely prevents the sun's heat from passing through. Combining this glass with IGUs, as in the Stegbar IGU, creates the ultimate energy-efficient glazing solution. Toned -- the colour (tone) of the glass 'shades' the inside of a home by reducing the amount of the sun's heat entering through the windows; cooling, reducing glare, and cutting up to 99 per cent of UV radiation. Laminated -- provides security from break-ins and reduces the transfer of noise. Look out for the WERS stars for the best option in energy efficient windows. WERS (Window Energy Rating Scheme) rates the energy impact of windows in housing anywhere in Australia on a scale from 0-10. The more stars the better. what is WERS? 64 greensmart 2009 Photo courtesy Stegbar Timber windows are also thought to be naturally better at preventing heat flow, but thermally broken aluminum window frames are specifically designed to stop the transfer of heat (by 'breaking' the thermal link between indoors and outdoors). The simplest and oldest solution is shading -- either internally or externally with curtains, awnings, shutters or shade sails -- to protect the windows or doors at various times of the day or season from unwanted solar heat gain. Ultimately, some of the key things you need to remember when choosing doors and windows are: • How many? • What type? • Where will they be placed? • Will they be exposed to full sunlight? • What sorts of things can you do to control solar heat gain? gs For more information: Stegbar www.stegbar.com.au Wintec www.energyratedwindows.com.au Aspect Windows www.aspectwindows.com.au Window Energy Rating Scheme www.wers.net