Low-E is so common now, but did you know that digital watches are just as old as Low-E coatings but there is a lot of mystery surrounding the coatings but not the watches, even though it is a window people look out of every day. In order to explain 5 facts about Low-E coatings, first I have to tell what Low-E coatings are. Low-E Coatings or low emissivity is a coating on a piece of glass that better insulate a room. It has been 46 years since Low-E was introduced to the North American glazing market. The product has developed from a premium option limited to residential windows in cold, Northern markets, to now a standard window component across many glazing applications. With annual shipments exceeding 600 million square feet, Low-E is a testament to both the patience required in developing building-product markets and the success of the glass industry in enhancing the value of its product offering. Current developments in energy policy are likely to ensure continued strong growth.
When the skyscraper wars erupted in Chicago and New York in the 1920s and ’30s, architects began to consider how sunlight and solar heat gain through the towers’ extensive windows would affect occupant comfort. Thus, a revolution in glazing technology was ignited. Project teams began replacing leaky single-glazed windows with then-innovative double-glazed insulated glass units (IGUs) and incorporating iron-rich glass, with its signature green tint, to reduce solar heat gain for indoor climate control. There are actually two different types of Low-E coatings: passive Low-E coatings and solar control Low-E coatings. Passive Low-E coatings are designed to maximize solar heat gain into a home or building to create the effect of “passive” heating and reducing reliance on artificial heating. Solar control Low-E coatings are designed to limit the amount of solar heat that passes into a home or building for the purpose of keeping buildings cooler and reducing energy consumption related to air conditioning.
It wasn’t until the energy crisis in the 1970s, however, that the U.S. government began funding research for a higher-performing glass to combat the amount of energy—and money—leaking out of windows. The Lawrence Berkeley National Laboratory (LBNL), in Berkeley, Calif., estimates that inefficient windows—essentially holes in otherwise-solid building masses—cost U.S. consumers $40 billion annually in energy loss. The demand for efficient technologies has continued to grow since. Glass manufacturers now offer several high-performance products, from reflective coatings to dynamic glazing to address this need. These technologies give architects a broad palette to design what they want in terms of aesthetics and energy efficiency, which advises clients such as the Glass Association of North America on energy-efficient windows, glass-coating performance, and building-code development. now let’s get to the facts
1. Both types of Low-E glass, passive and solar control, are produced by two primary production methods – pyrolytic, or “hard coat”, and Magnetron Sputter Vacuum Deposition (MSVD), or “soft coat”. In the pyrolytic process, the coating is applied to the glass ribbon while it is being produced on the float line. The coating then “fuses” to the hot glass surface, creating a strong bond that is very durable for glass processing during fabrication.
2. When heat or light energy is absorbed by glass, it is either shifted away by moving air or re-radiated by the glass surface. The ability of a material to radiate energy is known as emissivity. In general, highly reflective materials have a low emissivity and dull darker colored materials have a high emissivity. All materials, including windows, radiate heat in the form of long-wave, infrared energy depending on the emissivity and temperature of their surfaces. Radiant energy is one of the important ways heat transfer occurs with windows. Reducing the emissivity of one or more of the window glass surfaces improves a window’s insulating properties.
3. Since energy-efficient windows reflect much more sunlight than simple glass windows; when these windows are somewhat concave they can focus sunlight and cause damage. Damage to the sidings of homes and to automobiles has been reported in news stories. Low-E windows may also block radio frequency signals. Buildings without distributed antenna systems may then suffer degraded cell phone reception.
4. Since Low-E has two panes of glass when the heat inside your home tries to escape through the window, the Low-E glass reflects it back inside. The same thing happens when outdoor heat tries to enter your home. This results in a more comfortable indoor environment regardless of the weather.
5. It restrains around 40 – 60% of heat energy, which would have been lost by the ordinary glass, and helps lower heating and cooling costs, which account for 4% of the total annual US energy consumption. In 2017, about 4,015 billion kilowatt-hours were used in electricity alone, which means that 1,003.75 billion kilowatt-hours were used just to heat and cool buildings; imagine if no windows were Low-E and all of our cooling and heating systems were going full speed all the time.