Save money on your energy bills year on year and make your home a warmer and more comfortable place to live with ‘A’ Rated Windows.
Just like washing machines and fridge freezers, windows are now rated for energy efficiency on a scale from ‘A’ to ‘G’. The most efficient products are ‘A’ rated.
The Energy Index (kWh/m2/year) is one of the most important values, as it sets out the amount of energy lost or gained by a window. The value is displayed in terms of kilowatt-hours per square metre of glazing per year. Energy lost is displayed as a negative figure, and energy gained by a positive number. For example, 1kWh/m2/year means that the window gains a kilowatt of energy for each square metre of glazing over the course of a year; whereas a value of -1kWh/m2/year means that the window loses a kilowatt of energy per square metre in a year. So the higher the number, the greater the energy conserved – and the more money saved.
Thermal Transmittance (U-Value) indicates the amount of heat energy lost through a window, set out in kilowatt-hours per square metre of glazing per year, and is a contributing factor to the Energy Index value above. The lower the U-value, the less energy is lost, and the more efficient and economical the unit.
Solar Factor (G-value) represents the amount of solar energy that is gained through the window over the course of a year, once again in terms of kilowatt-hours per square metre. The higher the value, the more energy gained and the greater the saving.
Effective Air Leakage (L-value) is the amount of air that is leaked through the window over the course of a year, also a contributing factor to the Energy Index rating above. The modern sealed unit should have a zero-rated value, meaning no air leakage and no energy lost.