How Low-E Glass Works

glass is one of the most popular and versatile building materials used today one reason is that the available solar and thermal performance options are constantly improving one-way performance can be improved is through the use of passive and solar control low E coatings today we'll talk about how these Coatings work and the impact they have on a building's energy performance we'll cover an overview of the solar energy Spectrum the definition of emissivity how low E Coatings work the two different types of low E Coatings and how low E Coatings improve a Windows performance let's begin with a brief overview of the sun's energy Spectrum ultraviolet light visible light and infrared light all occupy different parts of the solar spectrum and the differences between the three are determined by their wavelengths ultraviolet light which is what causes fabrics and wall coverings to fade has wavelengths between 300 to 380 nanometers visible light occupies the part of the spectrum between 380 and 780 nanometers infrared light which is transmitted as heat into a building begins at wavelengths of 780 nanometers solar infrared is commonly referred to as shortwave infrared heat radiating off of warm objects has longer wavelengths than the Sun and is referred to as long wave infrared low E Coatings have been developed to prevent as much ultraviolet and infrared light from passing through as possible while optimizing the amount of visible light transmitted when heat or light energy is absorbed by glass it is cooled by moving air or re-radiated by the glass surface the relative ability of a material surface 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 temperatures of their surfaces radiant energy is one of the most important ways heat transfer occurs within Windows reducing the emissivity of one or more of the window glass surfaces improves a Windows performance and insulating properties this is where low E glass Coatings come into play for example uncoated glass has an emissivity of 0.84 while solar band 70 solar control low e-glass has an emissivity of 0.02 low E glass is a microscopically thin transparent coating that reflects long wave infrared energy or heat some low E Coatings also reflect significant amounts of shortwave solar infrared energy but we'll get to that later let's talk about how low E Coatings work when interior heat tries to escape to the cold outside during the winter the low E coating reflects the heat back inside reducing the radiant heat lost through the glass and the reverse happens during the summer to use a simple analogy low E glass works the same way a thermos does the thermos has a silver lining that reflects the temperature of its contents back in the temperature is maintained because of the reflection that occurs as well as the insulating benefits that the air space between the inner and outer shells provide similar to an insulated glass unit since low E glass is comprised of extremely thin layers of silver or other low E materials the same Theory applies the silver low heat coating reflects the interior temperature back inside keeping the room warm or cool there are two different types of low E Coatings passive low E and solar control low E most passive low E Coatings are manufactured using 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 or a hard coat that is very durable during fabrication finally the glass is cut into stock sheets of various sizes for shipment to fabricators passive low E Coatings are good for very cold climates because they allow some of the sun's shortwave infrared light to pass through and help Heap the building during the winter but still reflect the interior long wave infrared energy back inside most solar low E Coatings are manufactured using the magnetron sputtered vacuum deposition or msvd process the coating is applied offline to pre-cut glass in a vacuum chamber at room temperature this coating sometimes referred to as a soft coat needs to be sealed in an insulated glass or laminated unit and has lower emissivity and Superior solar control the best performing solar control Coatings are msvd and they are ideal for mild to hot climates that are dominated by air conditioning use in an insulated glass unit low E Coatings can be applied to the various surfaces depending on the type of coating the first surface faces outdoors and never has a solar control or passive low E coating solar control low E Coatings are typically msvd soft coats which is not durable enough for exposure to the outside elements the second and third surfaces face each other inside the igu and are separated by an airspace in an insulated spacer most msvd solar control low E Coatings and pyrolytic passive low E Coatings are applied to these surfaces the fourth surface faces directly indoors some pyrolytic hard coats can be applied to this surface if they are durable enough to withstand exposure to Interior elements whether a low E coating is considered passive or solar control they offer improvements in performance metrics here are some of the measures used to determine the effectiveness of glass with low E coatings new value is the rating given to a window based on how much heat loss it allows visible light transmittance is a measure of how much light passes through a window solar heat gain coefficient is the fraction of solar radiation admitted through a window directly transmitted absorbed and re-radiated inward the lower o Windows solar heat gain coefficient is the less solar heat it transmits light to solar heat gain is the ratio between the windows solar heat gain coefficient and its visible light transmittance rating as a general rule passive low E Coatings work well in heating dominated climates while solar control low E Coatings are typically recommended for cooling dominated climates to wrap up today we covered the solar energy Spectrum the definition of emissivity how low E Coatings work the types of low E Coatings and how low E Coatings improve a Windows performance when thinking of Windows size tint and other aesthetic qualities come to mind but as you've seen low E Coatings play an important role in the overall performance of a window they can reduce a building's Reliance on artificial heating lighting and cooling as well as the related energy costs for more information about low E Coatings or to ask any glass question please visit vitroglazings.com or call 855 vtrogls 855-887-6457

Channel: Vitro Architectural Glass

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Id: kBldz_Ss8GA

Length: 7min 33sec (453 seconds)

Published: Fri Oct 14 2022