Over the last twenty to thirty years, the technology we use in window construction has developed quite remarkably. Compare a double glazed window from the 90s with one installed today and you will see some big differences in the design and structure, everything from the underlying frame to the glass used in the production process.
The type of material and design that is used for a window frame will determine its overall energy efficiency. There are a number of materials utilised nowadays including traditional wood, aluminium and uPVC all have which have their own pros and cons.
Aluminium and other metal frames have one drawback in that they readily conduct heat which on the surface would make them unsuitable for a window where you are looking to insulate from the outside cold. They are, however, lighter and stronger which is why they are used in big builds such as office blocks and skyscrapers. Heat loss through the frame is usually reduced by introducing an insulating layer into the design.
Fibreglass is actually a poor conductor of heat so is an ideal material for making window frames. They usually have air cavities which are then filled with insulating material.
PVC and uPVC Frames
Probably the most popular type of window frame on the market nowadays because they are cheap to produce and fairly hard wearing. Polyvinyl Chloride (PVC) is resistant to moisture and doesn’t have to be painted and with insulated cavities they generally produce high levels of thermal efficiency.
Particle board and laminated strand lumber are largely used in composite frames which are often chosen over normal wood frames because they have better thermal properties but are also good at reducing condensation. They generally last a lot longer than wood frames.
Often chosen more for aesthetic reasons over than technical ones, wood frames can expand and contract with heat, cold and damp. They are pretty good insulators but require more maintenance than window frames made out of other materials such as uPVC or composite.
Glazing and Glass for Windows
The other factor that you need to consider when choosing your windows is the type of glass and its treatment. There are various energy efficient solutions on the market and being aware of them can help when it comes to selecting the right supplier or installer.
- Gases: First of all, the gap between the two window panes in double glazing is not air. It is usually an inert gas such as argon or krypton which are better thermal insulators. Because the gasses are inert they are harmless if they escape into the atmosphere so you are not putting yourself or your family in harm’s way by choosing them.
- Heat Absorbent Glass: Many double glazing products now have tinted glass that absorbs some of the solar radiation coming from outside. There are various types but they do not generally impact on the U Factor for windows.
- Low Emissivity Coated Glass: One of the more recent developments in glazing technology, low-e windows can reduce heat loss by as much as 30 to 40%. It is a very thin layer of microscopic metal or oxide that is invisible to the naked eye and is usually added during the manufacturing process. All A rated windows, the most efficient, will have a low-e coating which makes them slightly more expensive than normal windows.
- Reflective and Spectrally Selective Glazing: These are coatings that reduce the amount or type of light that comes through your window and are more applicable to hotter climes than the UK. Reflective coatings reduce the amount of solar radiation and glare coming through your window. Spectrally selective glazing uses a type of low-e coating that is more generally designed to reduce infrared heat.
The Future of Windows
Technology is always improving and more efficient glass and frames are constantly being developed. One area where the insulation our windows provide could well combine with our ability to create electricity or heat energy is with the development of solar windows. Future projects could have transparent solar panels installed on windows and doors that will make us all even more energy efficient. The technology is still in its early days but could revolutionise the way we view the double glazing industry in years to come.