Low E Glass
Low-E glass is a type of energy-efficient window glass designed to reduce the amount of heat transfer from inside to outside and vice versa. It is one of the most efficient ways to keep a house warm in winter and cool in summer while reducing energy costs. Low-E glass works by reflecting long-wave infrared energy (heat) away from the pane, while at the same time allowing short-wave visible light to pass through it. This helps maintain a comfortable climate indoors while minimizing energy loss to save money on heating and cooling bills.
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What is Low E Glass?
Low-E glass is a special type of window glass designed to minimize the transfer of heat from inside to outside and vice versa. It has an invisible metallic or ceramic coating, often called a “low emissivity” (Low-E) coating, applied to one or more surfaces of the glass that helps reflect heat back into a room instead of letting it escape. Low-E coatings are available in varying degrees depending on climate conditions and the amount of solar gain desired. The higher the number, the higher the level of insulation provided by the low-e coating.
How is Low E Glass Made?
Low E glass is made by adding an invisible coating to the window glass. This coating, called a “low emissivity” or Low-E coating, reflects heat back into a room instead of letting it escape. There are two different ways to make Low E glass: hard coat and soft coat. Hard coat involves spraying a thin layer of silver onto the surface of the glass at high temperatures, while soft coat windows have 2-3 very fine layers of silver added to them.
Soft Coat vs Hard Coat
The main difference between soft and hard coat Low-E glass is in their respective manufacturing processes.
Hard coat is manufactured using a pyrolytic process involving the application of tin oxide directly to the molten glass on the float line, fusing with the glass and producing a durable coating which can be used for everything from windows, doors all the way to storm windows and building facades.
Soft coat low e uses fewer layers of silver applied at room temperature in a vacuum chamber. The finish remains fairly delicate which is why it’s only used for windows, doors, and other non-structural applications.
Soft coat also has slightly better insulating properties than hard coat, but requires additional care during installation since the coating is easily damaged.
Advantages of Low E Glass
- Energy effiiciency: Reduces heat loss and solar heat gain, which can significantly lower energy bills.
- Comfort: Helps maintain indoor temperatures, reducing the need for heating and cooling.
- UV protection: Helps block harmful ultraviolet (UV) rays, which can cause fading and damage to furnishings and floors.
- Glare reduction: Reduces glare from natural light, improving visual comfort and reducing eye strain.
- Less condensation: Helps reduce condensation on glass surfaces, keeping windows dry and reducing the growth of mold, mildew, and bacteria.
Factors to Consider When Buying Low E Glass
Low-E (Low-emissivity) glass is designed to control the amount of heat that passes through it by reflecting or absorbing the infrared (heat) portion of the solar spectrum and allowing the visible light to pass through. When selecting Low-E glass, you should consider the following:
U-value (U-factor): A measure of the glass’s thermal conductance, with a lower U-value indicating better insulation.
Solar Heat Gain Coefficient (SHGC): A measure of the glass’s ability to block heat gain, with a lower SHGC indicating less heat passing through the glass.
Visible Light Transmittance (VLT): A measure of the amount of visible light passing through the glass, with higher values indicating more light transmission.
Coating type: Low-E coatings come in a variety of types, including pyrolytic, magnetron sputtered, and hard-coated, each with its own characteristics and benefits.
It’s important to consider the climate and specific needs of the building when selecting Low-E glass, as the right balance between U-value, SHGC, and VLT will depend on the building’s orientation, shading, and overall energy goals.