Low-emissivity glass (or low-e glass as it is commonly referred to) is a type of energy-efficient glass designed to prevent heat escaping out through your windows to the cold outdoors.
Hard Coat Low-E glass has a thin layer of molten tin poured over it while the glass is still slightly molten. The tin welds to the glass making the coating very strong and difficult to scratch or remove.
Soft Coat Low-E glass has silver, zinc, or tin applied to it in a vacuum chamber filled with an electrically charged inert gas. Atoms of the coating metal are sputtered onto the surface of the glass where they stick.
Soft Coat Low-E glass has better insulating qualities than Hard Coat Low-E glass. In double glazing units filled with inert argon, the R value (measure of resistance to heat loss) is 4.35 for soft coat, and 2.75 for hard coat. A single pane of regular glass would have an R value of below 1.
An ordinary glass will allow solar energy to pass from one side of the window to the other. This includes the relatively narrow spectrum of visible wavelengths, as well as those higher and lower wavelengths (known respectively as infra-red and ultra-violet light).
Ultraviolet (UV) light, visible light and infrared (IR) light all occupy different parts of the solar spectrum – the differences between the three are determined by their wavelengths.
Ultraviolet light, which is what causes interior materials such as fabrics and wall coverings to fade, has wavelengths of 310-380 nanometers when reporting glass performance.
Visible light occupies the part of the spectrum between wavelengths from about 380-780 nanometers.
Infrared light (or heat energy) is transmitted as heat into a building, and begins at wavelengths of 780 nanometers. Solar infrared is commonly referred to as short-wave infrared energy, while heat radiating off of warm objects has higher wavelengths than the sun and referred to as long-wave infrared.
Protection from UV rays
We offer spectrally selective low-E glass that, when laminated, blocks 99.9% of the sun’s harmful UV rays.
Large windows can let in beautiful light, but can also contribute to the degradation of home furnishings.
UV light exposure is a frequent culprit in fabric and pigment fading, plastic deterioratoin and changes to the apperance of many types of wood. Spectrally selective glazing is high-performance glazing that admits the highest amount of daylight possible, while filtering ultraviolet (UV) light and other main causes of fading. The United States Department of Energy has established a Light-to-Solar Gain Ratio of 1.25 as the minimum measurement for glazing to be classified as spectrally selective.
two type of low-e coating lass:
- passive low-e: suitable for cold climate
- solar low-e: suitable for hot climate
Low-e Coating Performance Measures
The measure of heat loss is usually expressed in terms of Ug-value, which is the rate of heat loss in Watts per square metre per degree Kelvin temperature difference between inside and outside (expressed as W/m2 K); the lower the Ug-value, the better the insulation of the product.
Performance factors are as follows:
- U-Value: This is used to measure internal heat loss during cooler periods. The lower the number, the greater the insulation.
- Solar Heat Gain Control (SHGC): Low SHGC values can result in significant savings in utility costs.
- Solar Factor: This is the percentage of total solar energy (or heat from the sun) able to pass through the glass.
- UV Transmission: UV (ultraviolet) transmittance. Reducing UV rays means less fading.
- Visible Light Transmittance: This is the percentage of visible light directly transmitted through the glass.
A good glass
- thereby retaining heat within a building, whilst maximising natural light transmission.
Solar Control Low-e Glass
Pilkington Eclipse Advantage
Şişecam performance for 4/20/4, toughened, low-e, argon gas filled:
- U-value: 1.1
- Solar Energy Direct Transmittance: 51%
- Solar Energy Reflectance Outdoor: 28%
- Solar Energy Absorption: 21%
- Solar heat-gain coefficient (Solar factor / g): 55%
- Shading coefficient: 0.63
- UV transmission: 38%