Understanding how heat escapes through glass is half the battle to understanding the value of double glazing. Knowing how double glazing prevents heat loss through windows will enable you to judge the effectiveness of your current windows.
How Heat Escapes Through Glass
Most of us assume that heat escapes through glass as radiation. However, the major part of heat loss through glass is due to conduction. This is because heat can pass directly through a poor insulator such as glass by conduction. As well as this, there is also a lot of radiant loss. The warmth radiates off all of the internal surfaces in a room and this is then lost through the glass of the window as if the window were an open fire. Heat is lost up the chimney, and also it is lost through the sides of the fire place.
What The Gap Between Panes Does
The gap between the two panes of glass is the most important part of a double glazed window and this typically contains air or a gas such as argon. The air or gas in the gap conducts heat much more slowly than solid glass and this is why warmth from inside a room finds it much harder to escape through double glazing than it does through single glazing. The width of the gap between the two panes also affects the performance of double glazing. In general, a wider gap is better than a narrow one but only up to a certain point.
Why Low-E Coatings Matter
A lot of modern double glazing features a low-E coating on the inside of the glass. This is a very thin layer of metal which allows sunlight to pass through but reflects heat back into the room. The coating works in a similar way to the foil backing on a radiator, reflecting heat back into the room rather than it escaping through the walls. Units with low-E coatings can lose less heat than identical non low-E units.
The Overlooked Job Of Spacer Bars
The spacer bar is another common area where heat loss occurs. Older aluminium spacer bars conduct heat and create a cold bridge along the glass edge where condensation occurs and heat escapes. Modern warm-edge spacer bars are made from reinforced plastic and stainless steel composites and significantly reduce the edge heat loss. Try running your hand along the edge of an old window on a cold day and you will feel the edge heat loss.
Frame Material Changes The Numbers Too
uPVC frames contain a number of hollow chambers internally. By filling these with air, uPVC can offer good levels of thermal insulation at an affordable price. Aluminium frames on the other hand conduct heat. To combat this, aluminium frames use thermal breaks. These are insulating materials that are incorporated into the frame to stop heat flowing from the inside of the property to the outside. When comparing Double Glazing Cardiff quotes for older properties, ensure that the frames and spacer materials offered by different companies are comparable. The difference in heating costs is considerable.
Draughts Cost More Than People Expect
In addition to the frames and glass, the seals and gaskets within a window sash must be of good quality and fit well. They must be of a type that will compress to fit the sash or frame and will be of sufficient cross section to form a tight seal when closed. A well fitted window will stop uncontrolled air leakage, or draughts, and such items are far more damaging than people actually realise when it comes to heating a home and retaining warmth within.
What Savings Look Like In Practice
Double glazing can cut heat loss through windows by a substantial amount. In terms of carbon and energy use in the home, double glazing is one of the most effective home improvements, provided it is properly specified for the property. However, improved windows need to be used in conjunction with sensible behaviour, such as not putting the heating up in a draughty room. Also, radiators need to be bledin order to distribute heat properly. Finally, closing curtains at night will also help to keep warmth in.
Signs Your Current Windows Are Underperforming
Draughts are a sign of poor gasketing. Cold patches on walls near to windows indicate poor insulation or failing spacer bars. Evidence of condensation between the glass panelof your windows (as opposed to on surfaces within the window) is a clear indication of failure of the seals between the panes, and a consequent loss of the insulating gases within the unit.
Like so many components in your home, your windows are usually silent; only giving attention when they fail. Many components fail slowly over time; gradually losing performance until one day they collapse. The frames of your windows are no exception – they quietly allow heat to escape every year.