The World Green Building Council states that building operation is responsible for 28 per cent of global emissions . Updating windows is an easy way to significantly increase the efficiency of a home and could save up to £ 155 a year on energy bills . The rate of heat transfer through a window can be measured by its U-value , which for well insulated windows is low . A U-value is calculated by looking at how many watts of energy are lost through a square metre of window , for every degree Kelvin difference in temperature between the inside and the outside .

As well as selecting windows with a low U-value , buyers should make sure the windows comply with Building Regulations Part L , which relates to thermal efficiency , and Part F for ventilation . Windows should also have at least an A rating from the British Fenestration Rating Council ( BFRC ).

Ask about the glass

The qualities of a window ’ s pane have a significant influence on its overall efficiency . Windows with double glazing are far more efficient than those with single

panes , as they have more glass to slow heat loss and also have an insulating layer of gas between the panes .

Windows with a higher glass thickness will also be more efficient , as well as those with an additional functional coating . For example , Euramax manufactures A rated double glazed uPVC windows that have 28 millimetre ( mm ) toughened low emissivity ( Low-E ) glass . Low-E windows have an invisible interior coating that reduces the infrared and ultraviolet light that passes through , helping to keep heat inside the building .

However , it ’ s not just the glass that matters - it ’ s also what ’ s between . The gaps between the panes are filled with gas , which is usually either air or argon . Argon gas ’ thermal conductivity is over 60 per cent less than air , but is a more expensive option and if there ’ s even one small gap in the window , then the argon will escape and be replaced with air . Air-filled windows provide a simpler and cheaper option that still provides good insulation .

There are other features to consider between the glass panes , such as the size of the air gap and the material of the pane

spacers . If the gap between the panes is too wide , the air can form a convection current and begin to circulate , and if it ’ s too small then heat or cold can easily radiate across - both reducing the window ’ s efficiency . Typically , an air gap of around 16 mm is satisfactory . It ’ s important that the pane spacer bars contain little to no metal to reduce thermal conductivity , which are known as ‘ warm edge ’ spacer bars .

Think about the frames

Lastly , when selecting an energy efficient window , the material of the frame that surrounds the glass is also a factor to consider . Wooden frames offer the most insulation , but can be susceptible to warping , rotting and insect infestation , and the resulting damage can significantly lower a window ’ s efficiency . Frames made from uPVC offer a good allround option , which is why they have become a popular choice . uPVC frames are lower maintenance

and much cheaper than wood , while still providing high efficiency .

What ’ s more , uPVC can strike the perfect balance between practicality and aesthetics , as they are available with far more design options than just the classic white . At Euramax our uPVC windows come in a variety of colours , such as Anthracite Grey , Chartwell Green and Golden Oak , which even comes with a woodgrain effect finish — giving a traditional look to modern technology .

Outdated windows are a large source of energy loss , and upgrading to energy efficient windows will lower the building ’ s environmental impact as well as reduce energy bills . By carefully selecting insulating windows that include key features such as thick glass , double gazing and an efficient frame material , buyers can ensure their upgrade is a valuable investment .

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