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Window Adaptation: Insulation for sound proofing, and heat and energy efficiency

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Window Adaptation: Insulation for sound proofing, and heat and energy efficiency

by Megan Macpherson

Glass windows are an integral element in the modern home design. Views from the home maximise its value, as well as letting the outside world into your living space. However, glass is the main area of the home through which heat and energy is gained and lost, in relation to the outside temperature.

Passive solar heating works to keep temperatures in the home regulated, by maximizing heat gain and minimizing heat loss. Double glazing, tinting and coating options on windows reduce temperature change within the home against outside climate changes. This therefore reduces the cost and energy used to heat or cool the home, being both economical and environmentally sustainable.

Introduced in 1995, the Window Energy Rating Scheme enables windows to be rated and labeled for their annual energy impact on a whole house, in any climate of Australia. The Window Energy Rating Scheme (WERS) is jointly owned by the Australian Window Association (AWA) and the Australian Glass and Glazing Association (AGGA). WERS was supported by the Australian Government's greenhouse office to help improve environmental sustainability, including reducing greenhouse gas emissions, and improving energy efficiency. Windows rated under this scheme carry a label with pictures of stars that denote the effectiveness in the home for heating and cooling.

Effective 1 May 2006 the Buildings Code of Australia (BCA) has included enhanced energy efficiency ratings in its 2006 edition. The total window system will be included in the measurement of energy ratings for glazing, as opposed to individual parts. This is an excellent step towards simplifying energy ratings to benefit consumer understanding. However, for the home renovator, understanding the individual details of window components and their effectiveness will provide better choices when choosing products.

When you are investigating the best way to make your windows more energy and heat efficient, there are a number of factors you must take into consideration. These include the types of insulation available, and understanding the measurements of effectiveness used to rate the products.

Double glazing minimises heat transference by an insulating air pocket between two panes of glass. Double glazing also protects against condensation, and helps improve sound proofing.

Low-e stands for low emissivity and is a microscopically thin coating of metal oxide on the glass that reduces the U-Factor. In other words, it lets light in but reflects UV rays, and reduces the amount of heat radiating from the glass.

The U-factor measures the effectiveness of a windows insulation. This factor takes into account all aspects of the window, including the glass, frames and seals. These factors are variables, depending on the material they are made from, thus affecting the overall U-factor. The lower the U-factor, the better the window will perform.

Solar Heat Gain Coefficient (SHGC) measures the transference of solar heat through a window. The lower the SHGC the less heat is transferred, and it is conveyed as a number between zero and one.

Visible Transmittance (VT) refers to how much light is visibly transmitted through the glass. VT is a number between zero and one and a higher number means more light will pass through.

Improving windows to regulate heat loss and gain is useless if you have cracks in the system. Air that can enter or escape from the window area through a crack or through lack of sealing in the frame can undermine the effectiveness of the window.

The mixed climates in Australia make windows a key focus of the building envelope for the home renovator. If you have any experiences dealing with windows that you would like to share, why not email me at and be our 'renovator of the week'. It's a great way of sharing your story with our proud nation of home renovators.

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