Why is this important? UV rays are invisible rays of light emitted by the sun. UV rays are responsible for fading upholstery, burning skin and, over the course of many years, damaging building materials. Infrared light is heat that warms your home during the winter.
By deflecting both types of light back out into the environment, low-E coatings help keep your home warm in winter and cool in summer 2. In a way, low-E coatings sound almost too good to be true. How can glass enable light to enter or exit the home, while preventing heat loss in the winter and heat entry in the summer? Low-E coatings are not visible to the naked eye. However, they are still reflective, just like the silver coating on the inside of a thermos. This reduces the emissivity of the glass and prevents certain types of light from entering or exiting the home.
Low-E coatings are selectively reflective, and only allow light of a certain wavelength and frequency to pass through glass 3. For many homeowners, these benefits can result in significant cost savings over time. In some cases, installation of new energy efficient windows may even improve property values. Home buyers like to purchase homes that have energy-efficient , money-saving features like low-E windows 5. Light takes many forms, but visible light occupies only a fraction of the spectrum.
Other parts of the light spectrum include short-wave solar energy UV rays and long-wave infrared heat. Low-E glass has a coating that reflects short and long-wave infrared rays. The only light that passes through low-E coatings is visible light.
Low emissivity glass prevents heat transfer and ensures that visible light is able to pass through the glass in both directions.
Low-E coatings come in two types: hard coat and soft coat. Hard coat is made by pouring melted tin on the glass, while soft coat low-e glass is made with silver, tin or zinc that is applied to the glass in a vacuum. Soft coat low-E coatings have a higher R-value, so they provide better insulation than hard coat 6.
During the summer, this reflective coat sends heat back into the atmosphere instead of allowing it to enter into the home via the glass. During the winter, the reflective coat sends heat back into the home to keep the interior of the house comfortable.
This innovative coating, along with the space between the panes of glass, serves as an excellent insulator for residential homes 7. Depending on how many coatings are applied to the window, low-E coatings can cause a window to look somewhat tinted.
This should not affect the clarity of the view through the window and is usually negligible. Glass is a natural insulator, like woods and plastics, which means it is a good absorber of heat. Then, this heat energy becomes either unwanted solar heat gain in the summer or unwanted thermal loss in the winter.
The primary benefit of low E glass is to improve the insulating performance of your windows. With better insulation, you achieve a more comfortable home without having to turn up your heating or cooling systems. Whether you are battling high energy bills or simply want a more comfortable home and a lower household carbon footprint, low E glass can make a significant difference, especially in the long-term. UV rays can damage your indoor furnishings over time.
So, enjoying the sunlight flooding into your home means your expensive furniture and brilliantly coloured carpets will eventually fade.
It will also block the majority of UV light. Low E glass still allows most of the visible light spectrum to flow through. Important question! How does a low emissivity coating stop glass from giving off as much heat? It does this by reflecting the infrared and UV spectrum, whilst still letting the visible light spectrum pass through. The coating that is manufactured onto low E glass serves as a reflective service, causing heat energy to bounce back from where it came from.
Yes they are, making low E glass an attractive option in both cooler and warmer climates. The same principal that causes unwanted solar heat energy to bounce off your glass and back outside, will help to keep your indoor heat in during the winter.
This allows you to rely less on your air conditioning to cool your home. Low E glass is made by applying a microscopically thin coating to one surface of the glass. This coating is made up of multiple layers of reflective materials, consisting of different metals, metal oxides and metal nitrites.
Today, most window professionals work with a special type of low E glass known as soft coat low E, which has a coating with a thickness of one-ten thousandth of a human hair. Soft coat glass is made by depositing the coating to the surface in a vacuum chamber after the glass has been manufactured. This process is known as sputtering, which is why soft coat low E is also sometimes called sputtered glass.
Another way to make low E glass is to bond the metal oxide layers to the glass when it is still in its semi-molten state. Essentially, the coating is baked on, creating a hard surface. In , the first low-emissivity glazing solution was brought to market in a bid to change this. The emissivity of a surface refers to the amount of energy it emits at specific wavelengths, with thermal energy usually being the focus.
A material is given a numerical thermal emissivity value of between 0 and 1, with a perfect reflector having an emissivity of 0 and the perfect absorber having an emissivity of 1. Breaking this down, standard glass with its thermal emissivity of 0. Clearly then, window glass needs some help in reflecting heat back into the home.
This is where low E glass comes in. Low E glass is essentially standard clear glass with a microscopic, transparent coating on its surface that is better at reflecting heat than the glass itself, creating a composition that has a lower emissivity than standard glass. Glass with a low E coating therefore keeps your home warmer by reflecting a higher proportion of the heat back into your home, and can keep you cooler by reflecting solar thermal energy from outside.
The coating used in soft-coat low E glass units tend to be that of a low-emissivity metal, such as silver. The first of the big advantages of low E glass is the supreme insulating power it adds to your windows.
Adding the soft-coat low E film allows your glass to have an emissivity as low as 0. So, when combined with other insulating tech, such as warm-edge spacer bars and argon gas-filled cavities, low E glass can be used to create an IGU insulated glass unit of real insulating potential.
Double-glazed units made with low E glass, and the aforementioned IGU tech, can have a U-value as low as 0. Translating this into a real-world scenario, low E glass might be the one for you if you have pesky family members fiddling with the thermostat on a regular basis.
With your home now a low-key toasty oasis sort of from November to March, familial thermostat offences will be at an all-time low. Remember how we said a low E coating reflects heat? Look out your window, what do you see?
Potentially making for some sweaty indoor summer conditions. So, if you were looking at a double-glazed window from the outside, the very outer surface and the very inner surface are off limits — leaving you with two sealed internal surfaces to which a low E coating can be applied.
The surface used is generally the internal surface of the inner pane. Putting the coating here has some optical benefits, but also allows the IGU to have lower solar gain statistics. Essentially, in much the same way that low E glass reflects heat back into the house, thermal energy from the sun is reflected away from your home. Thus, creating a cool, comfortable indoor summer environment — another of the big advantages of low E glass. Applying this to another real-world scenario, kids take ages to eat ice creams.
Comfortable Summer indoor temperatures aside, the solar reflective properties of low E glass may very well increase the refractory period between the initial scoop, and the dreaded drip. As a former ice-cream-lobbing infant myself, I can confirm the validity of this. Through a similar mechanism to which thermal radiation is reflected, low E glass is also able to prevent the vast majority of UV radiation from entering your home.
This not only protects your family, but also your furnishings, as UV light has a particularly annoying habit of having a sort of bleaching effect on your carpets and fittings, causing them to lose their colour.
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