The benefits of double glazing are many including making your home more attractive, improving the value of your home, reducing noise pollution and of course, reducing heat loss from your home. But how exactly do these double glazing units work and how do they stop heat from leaving your home and the cold air from entering?

Apart from the roof, your windows are the quickest way for heat to escape your home. While many of us want light and airy homes, we can pay the price of having so much glass in increased energy bills and a colder home. This can be clearly seen on a frosty morning when non-insulated homes have no frost on their roof due to the heat escaping and preventing it from forming. The same can happen with your windows.

How does double glazing work?

Cold air can enter our home in many ways – through gaps under doors, through single glazed windows, down chimneys and via non-insulated lofts. While we can do plenty to eliminate these issues and get the air in our home warm – we can only prevent it from leaving the home via our windows by installing double glazed windows. Even then not all heat will be retained. So why is a double glazed unit better than single and why will it save us money?

A double glazing unit is essentially two panes of glass that are sandwiched together with an air or gas gap between. Usually the gap is around 16mm and this forms an insulating barrier to cold air from the outside and works to prevent warm air from escaping. You can have thick or thin frames, but these should also be insulated so the entire unit offers the best thermal resistance. This air insulation acts in the same way as the insulation you have in your loft – it prevents cold air from entering and warm air from leaving the home.

There are a number of different double glazing types you can choose from and each will offer their own benefits. UPVC units are the most common and offer the cheapest solution compared to wooden frames. The frames are also the most energy efficient. Metal and timber frames may look better on certain styles of house, but you can expect the thermal ratings to be lower. You can also choose different glass types to offer the very best heat loss reduction.

The ratings system

The British Fenestration Rating Council (BFRC) is the UK’s main authority on window ratings and they use a ratings system similar to those we are used to for appliances and even for our homes.

Your windows can be rated anywhere from E through to A++. The higher the rating the more thermally efficient your windows will be. Not all window installers will use this rating system, but this is a good benchmark to work from.

Things to think about when buying

  • To get the very best energy efficiency from your windows you need to choose double glazing units that have high ratings on the BFRC rating scale. The very best windows will achieve an “A” and will offer you the very best heat retaining properties. But be aware that these will be at a higher price point. Decide for yourself what level of protection your home needs.
  • You will also be looking for low-emissivity (low-e) glass which has an invisible coating of metal oxide on an internal pane. This works to let light and heat into your home, but reduces the amount of heat that can escape. You can have this coating on an outer frame to reduce sun glare, but it may not work effectively for heat reduction.
  • The larger the gap between the panes of glass on your double glazing unit, the better the heat retaining qualities. A gap of 16mm is recommended as a minimum.
  • If gas is used between the panes – in particular argon, xenon or krypton you can expect the units to be even more efficient, but air is also an excellent insulator. Again, due to the technicalities of filling a cavity with gas and ensuring it does not leak – gas filled solutions will be more expensive than plain air filled windows.
  • Look for units with insulated frames in UPVC as these offer the very best heat retaining qualities.

How much can I save?

According to The Energy Saving Trust the possible savings you can make on your energy bills once you install your double glazing can be substantial. If you choose an “A” rated unit and have a semi-detached home, the savings will amount to £85 to £115 per year. For most of us that is approximately 10 – 15% of our total energy bill – quite a saving and these savings will last for the life of the windows, which can be up to 20 years.

The average step up each level of the rating system approximately equates to a further 15% on the cost of the unit – but you may feel that the energy cost savings you make will mean this is worthwhile.

For most people, the reason they decide to install double glazing is because they want a warmer and more comfortable home. However if you fail to choose wisely and go for the cheapest or least efficient option you may find that the savings and benefits you had hoped for never materialise. Do you homework and you can achieve a warm and beautiful home easily.