HIGH PERFORMANCE GLASS

Architectural Glass is used as the transparent glazing material to make the transparent building walls and windows. As the demand of Architectural Glass is increasing it is required to tested and certified under the Indian Standard as per BIS. The Glass should be tested for the safety of consumers. It is mostly used as the building material because of its Transparency, Strength, Workability, Transmittance, and Recycle properties. These all properties should be satisfied under Indian Standard.

Glass is a transparent hard substance created when heat is applied to sand or quartz. It is a mixture of raw materials like Silica, sodium potassium carbonate, lime or lead oxide, and manganese oxide. It is inorganic, can be transparent or translucent, and can be molded into any shape.

Architects have been using glass for a very long time to enhance design, beauty, light, and energy usage. It’s not unusual to see designs that emphasize the use of glass as a primary building material.

Architects often use reinforced, toughened and laminated glass.

In modern architecture, glass is a highly versatile component. It can be used for several internal as well as external glazing applications. Be it staircases, façade, balustrades, doors, windows, external walls, shower cubicles, or room dividers – glass is everywhere!

However, due to its high surface emissivity, glass can absorb and emit the solar energy to the inside of the building – causing indoor overheating.

To combat this, advanced glass technologies are used to manufacture high-performance glass. They possess solar control and thermal insulation abilities to provide enhanced energy-efficiency.

Presently, there are three primary high-performance glasses available in the market. They are:

(a) Low E Glass:

Low emissivity glass commonly known as low-e glass has excellent thermal insulation properties. It allows only visible light to enter the room and thus gives protection from UV and infrared rays. In cold climates, they help in maintaining the temperature of interior, and provide energy efficient solution.

Low-E or Low-Emissivity glass is a type of high-performance glass that blocks out harmful UV and infrared rays of the sun. It only allows visible light to pass through.

It offers thermal insulation as a result of its low emissivity that decreases the absorption and transmittance of solar radiation. Because of this, low-E glass reduces the amount of heat ingress from the outside. At the same time, it traps the internal heat from escaping outside, making it ideal for the winter season. AIS Ecosense Essence is a perfect example of low-E glass.

(b) Solar Control Glass:

Solar control glass is a special oxide coated glass which transfers less amount of the heat in the building and also helps in reducing the glare of light entering. For tropical countries like India, this type of glass is very suitable as it helps in reducing the amount of air-conditioning required. It is used in skyscrapers as glass facades in modern buildings, conservatory roofs, air conditioned malls and showrooms, etc.

In solar-control glass, a special oxide coating is present that reflects away the harmful rays of the sun and prevents the heat from entering inside the structures. It also prevents solar glare, notorious for causing eye and skin infections. However, the glass does allow natural light to filter through, providing optimal daylight management. And consequently, lowers the reliance on air-conditioning and heating appliances. For single glazing applications, AIS Ecosense Edge is a solar-control glass with high insulation properties.

(c) Solar Control – Low E Glass:

For facades, which are in direct contact of sunlight, only low e glass cannot be used, as they will trap the heat inside, leading to overheating of interiors. In such case, solar control low e glass is used, which blocks solar radiation, as well as provides thermal insulation. An interesting example of its application is Bhurj Khalifa, where this glass is used to decrease the air conditioning cost.

As the name suggests, a solar low-E glass is a type of low-E glass that comes with solar control coating. In terms of performance, this glass possesses properties of both its parent glasses. It prevents overheating of interiors by blocking out the solar radiation and offering thermal insulation. In this way, the heat entering inside isn’t trapped, so it promotes a relatively cooler atmosphere.AIS Ecosense Excel has advanced solar control and double low-E coatings for best-in-class thermal insulation and solar control performance.

Factors to be considered in Glass Selection:

U-Value: U-value indicates the rate of heat flow due to conduction, as are sultof temperature difference between inside and outside. The lower the U-factor, lower the heat transferred through the glass. U-Value is measured in W/m2oK.

Shading Coefficient of glazing (SC): Shading coefficient indicates the extent of direct solar heat gain. Lower the shading coefficient, better the glazing in preventing solar heat gain.

Solar Heat gain coefficient (SHGC)

Shading coefficient =

Heat gain through 3mm clear glass

Relative Heat Gain (RHG): Relative Heat Gain is the combined effect of shading coefficient and U-value. The direct heat gain component can be as high as 90% vis-à-vis10%for conductive heat gain. Hence shading co-efficient becomes a very vital criterion in the selection of glazing particularly for tropical climates where solar intensity is high (600-900W/m2).

RHG =Direct heat gain +Conductive heat gain

=SC (Solar intensity)+U(Differential Temperature between inside and outside)

Visible Light Transmission of glazing (VLT): Visible Light Transmittance factor determines the visual performance of glazing. Visible Light Transmittance indicates the percentage of the visible portion of the solar spectrum that is transmitted through a given glass product. Higher the VLT, higher will be the light penetration. Visual performance is influenced by several factors like tinting (colourants added to the glass) and low – Ecoatings.