Do you know as part of the Window Energy Rating Scheme (WERS) rating, U-Value and Solar Heat Gain Coefficient are two crucial parameters to understand when you are about to select windows or doors for your house? This is because Australia’s property developers and home builders are required to build properties with energy efficient windows and doors. Generally, when these values are mentioned, they mean the value of entire window or door system (include frame, glass and seals), not the glass itself. Different from U-value and Solar Heat Gain Coefficient, R-value is mostly mentioned when referring to insulation values for walls, ceilings and floors. R-value depends on the type of insulation material used, its thickness and density.
U-value measures the ability of the product to avoid heat transfer. The lower the U-value, the greater the insulation performance of the windows or doors, that is the better to avoid heat loss or heat gain in the house via doors or windows. In Australia, the U-value rating for windows and doors products generally lies between 2.0-10.0 W/m2.K. In cold winter, low U-value windows and doors can be helpful in reducing heat loss within the house.
R-value also measures the ability of the product to avoid heat transfer, but mostly for walls, ceilings and floors. The higher the R-value, the greater the insulation performance of the products, that is the better to avoid heat loss or heat gain in the house via walls, ceilings and floors. Therefore, it is important to choose finishing and building materials with high R-value to improve thermal comfort in a house in cold winter.
Solar Heat Gain Coefficient
Solar Heat Gain Coefficient is often expressed as SHGC. It measures how well a window block the solar radiation. It is usually rated between 0 and 1. The higher the Solar Heat Gain Coefficient value, the more solar heat the window transmits. In order to increase thermal comfort and reduce energy use in cold winter, high Solar Heat Gain Coefficient value windows should be chosen to allow a greater amount of solar heat transferring into the house.