THE BUILDERS CHOICE energy efficiency
Image 1: Double Glazing
Image 2: Insulated Glass Units (IGU)
Image 3: Solar Heat Gain – SHGC
Glazing reacts thermally in two different ways, heat transfer due to a difference in temperature from inside to outside the building and solar radiation passing through the glass creating heat. The measurements for these are U Value and Solar Heat Gain Coefficient (SHGC). The lower the U Value the better the insulation performance and the lower the SHGC the less solar radiation passing through.
Tailor made IGU’s If you want to alter the function of the IGU you can do many things, change the glass type to a Low E, alter the size of the air space or add argon gas to improve the U Value. To lower the amount of solar heat gain, simply add tinted glass products and Low E to the IGU. To improve the acoustic values include heavier glass, laminated glass and have a 40 per cent difference in the two glass thicknesses, for example use a 6mm laminated acoustic glass product with 4mm glass in the IGU. To make the product secure and safe include laminated safety glass designed for higher security. The options are enormous with IGU’s to tailor them for the function you require. I often tell people it is a bit like visiting Subway and creating just about whatever you like. What IGU to use In colder climates you want to get the U Value as low as you can afford and have the SHGC high to allow the free energy from the sun to enter the home especially on the North with correct eave protection. This can be achieved by using clear glass, neutral Low E glasses and argon gas. It may be appropriate to reduce the SHGC on east and west elevations depending on the building design. In warmer climates you want to get the U Value as low as you can afford and reduce the SHGC to restrict the heat gain from the
Insulation – U Value
sun. This can be achieved by using tinted glass, tinted Low E and argon gas. Remember insulation is important in air conditioned and heated buildings, meaning no matter the climate IGU’s are an appropriate energy efficient solution and just need to be tailored to suit the climate and elevation. For acoustic performance in IGU’s the air space will not have an impact, so alter the glass types being used and vary the two thicknesses by 40 per cent, use special laminated acoustic glass products and remember the thicker the glass the better it will perform. For security and safety use glass products in the IGU that are developed for these purposes such as A Grade safety glass and special laminates. It is important to understand that when you install an IGU into a window system that the window system will impact on the performance of the IGU. There will be window systems designed specifically for all areas of performance covered in this article.
Why use IGU’s An IGU is still the best solution around the world for varying performance requirements and has been for many years. The use of IGU’s in the right window system will significantly reduce the need for heating and cooling in a building, reducing energy costs. I can say through experience visiting many homes that have used IGU’s the payback for the investment is instant as you feel the difference in the comfort of the home. There are some websites worth visiting with lots more information on energy efficient glazing products www.efficientglazing.net and www.wers.net BC Australian Window Association: (03) 9808 0069 / 0437 967 540, gary.smith@awa.org.au
The Builders Choice Magazine – December 2012 147