In an attempt to provide a useful comparison between alternative window constructions the British Fenestration Rating Council have defined a “Window Energy Rating” WER, ranging from A for the best down through B and C etc. This takes into account a combination of the heat loss through the window ( U value ), the solar gain ( g value ), and loss through air leakage around the frame ( L value ). For example, an A Rated window will in a typical year gain as much heat from solar gain as it loses in other ways. This provides better thermal performance than a typical wall.
How energy-efficient glazing works:
Double-glazed windows have two sheets of glass with a gap between them, usually about 16mm, to create an insulating barrier that keeps heat in. This is sometimes filled with gas. Triple-glazed windows have three sheets of glass, but aren’t always better than double-glazed windows: to choose the most energy-efficient window look for the BFRC rating and Energy Saving Trust Recommended logo.
Energy-efficient windows come in a range of frame materials and styles. They also vary, depending on:
- how well they stop heat from passing through the window
- how much sunlight travels through the glass
- how little air can leak in or out around the window.
- Glass: The most energy-efficient glass for double glazing is low emissivity (Low-E) glass. This often has an unnoticeable coating of metal oxide, normally on one of the internal panes next to the gap. This lets in light and heat but cuts the amount of heat that can get out.
- In between: Very efficient windows might use gases such as argon, xenon or krypton in the gap between the sheets of glass.
- Pane spacers: These are set around the inside edges to keep the two panes of glass apart. For maximum efficiency, look for pane spacers containing little or no metal – often known as ‘warm edge’ spacers.
In a Nutshell:
Basically, new double glazed units are coated with a special energy effiecient layer which traps solar energy in your home and have a special gas inside them and have a special edging bar.
We replace your existing glass (not the frames, just the glass) with the new energy efficient glass. No Mess. No fuss. All done in a day or less.