Description:

Building Material Category: Insulation Products

Building Component Type: Fenestration-Glass 

Alternative for Conventional Building Material: Conventional single-pane or standard double-pane clear or tinted float glass.

Introduction: Low-E Glass features a thin, invisible coating that reflects infrared light while allowing visible light to pass through. This coating helps to keep heat inside during the winter and outside during the summer, contributing to improved energy performance and comfort. Low-E Glass falls under the category of energy-efficient glazing materials. It is used primarily in windows and facades to enhance thermal insulation and control solar heat gain. Low-E Glass serves as an alternative to conventional single-pane or standard double-pane glass. Unlike traditional glass, Low-E Glass has a special coating that reflects infrared energy, reducing heat transfer and improving energy efficiency. Low emissivity (low-e) glass surpasses conventional glass by reducing heat transfer through windows, improving energy efficiency, controlling solar heat gain, enhancing indoor comfort, providing UV protection, supporting environmental sustainability, and offering versatility in building applications.

Composition: It consists of a clear glass substrate coated with a thin, transparent layer of metal or metal oxide (such as silver, tin oxide, or titanium oxide), which selectively sreflects infrared radiation while allowing visible light to pass through. The base glass is usually made of float glass or other standard glass types. The low-e coating is a microscopically thin layer of metal or metallic oxide applied to the glass surface. This coating can be applied to single, double, or triple-glazed units.

Applicability in Climatic Zone: Suitable for all climatic zones in India, contributing to energy efficiency by reducing heat transfer through windows and facades.

Use: It is primarily used for windows, curtain walls, and facades in residential, commercial, and institutional buildings to improve thermal performance and energy efficiency.

Thermal Performance: It offers enhanced thermal insulation by reducing heat transfer, thereby lowering heating and cooling loads and improving indoor comfort. Factors which affect thermal performance are emissivity of the coating, type of coating material, thickness of the glass substrate, and installation quality.

Thermal Conductivity: Low-E coatings themselves have very low thermal conductivity, typically around 0.03 to 0.05 W/m·K. However, the overall thermal performance of the glazing unit (including the glass and any air or gas layers) will differ based on the specific construction of the window.

Thermal Transmittance: The U-value measures the rate of heat transfer through the glazing unit. For Low-E Glass, depending on the configuration (e.g., single, double, or triple glazing), the U-value can vary: For Double-Glazed Low-E Glass, it typically achieves U-values ranging from 0.20 to 0.30 W/m²·K. For Triple-Glazed Low-E Glass it can achieve even lower U-values, often ranging from 0.10 to 0.20 W/m²·K.

Reduction in CO2 Emissions: Low-E Glass reduces CO2 emissions by improving a building’s energy efficiency. By minimizing heat loss in winter and reducing heat gain in summer, it lowers the need for heating and cooling. For instance, using Low-E Glass can reduce heating and cooling energy consumption by up to 30% to 40%, translating into significant reductions in CO2 emissions associated with energy production. The exact reduction depends on the building's location, design, and energy sources.

Salient Features:

• Enhanced Thermal Insulation: Low-e glass coatings significantly reduce heat transfer through windows by reflecting infrared radiation, thereby improving the thermal efficiency of buildings. This helps in reducing heating and cooling costs throughout the year.
• Solar Control: The selective coating allows visible light to pass through while blocking a significant portion of infrared and ultraviolet (UV) radiation. This reduces solar heat gain during hot weather, enhancing indoor comfort and reducing the load on air conditioning systems.
• Year-round Comfort: By maintaining more consistent indoor temperatures, low-e glass contributes to improved occupant comfort across different seasons and climates.
• Energy Savings: By reducing the need for heating and cooling, low-e glass helps lower energy consumption and greenhouse gas emissions associated with building operations, supporting sustainable building practices.
• UV Protection: Low-e coatings also mitigate UV transmission, which helps protect interior furnishings, artworks, and occupants from harmful UV rays.
• Durability and Longevity: The coatings are durable and do not degrade over time, ensuring sustained performance and minimal maintenance requirements.
• Versatility: Suitable for various architectural styles and building types, including residential, commercial, and institutional buildings.
• Environmental Benefits: Contributes to green building certifications and sustainability goals by improving energy efficiency and reducing the building's carbon footprint.

Indian Codes:

• IS 2553: Code of Practice for Glazing in Buildings, which covers general guidelines for glazing but may not specifically address Low-E Glass.
• IS 3548: Specification for Glass for use in Buildings – This standard may include general requirements for glass performance.

International Codes:

• ISO 9050: Glass in Building – Determination of Optical and Thermal Properties-It provides methods for measuring the thermal and optical properties of glass, including Low-E Glass.
• ASTM E772: Standard Test Method for Determining Solar Optical Properties of Materials-It includes methods for testing solar optical properties, relevant for Low-E Glass.
• EN 1279: Glass in Building – Insulating Glass Units-European standard for insulating glass units, including those with Low-E coatings
• ANSI Z97.1: Safety Glazing Materials Used in Buildings-It addresses safety performance for glazing materials, which can include Low-E Glass.

Manufacturers

• Saint-Gobain Glass India: It offers a range of Low-E Glass products, including high-performance glazing solutions.

Website: Saint-Gobain Glass India

• AIS Glass (Asahi India Glass Limited): It provides various Low-E Glass options under the brand name AIS Ecosense, designed to enhance energy efficiency.

Website: AIS Glass

• Guardian Glass India: It supplies Low-E Glass and other high-performance glazing products.

Website: Guardian Glass

• PPG Industries (India):  It offers a range of Low-E Glass products, known for their energy efficiency and performance.

Website: PPG Industries

• Pilkington India: It provides Low-E Glass solutions among other glazing products.

Website: Pilkington

• Jindal Architectural Glass: It includes Low-E Glass in its portfolio of architectural and building glass solutions.

Website: Jindal Architectural Glass

• ModiGuard: It offers a variety of glass products, including Low-E Glass for energy-efficient building applications.

Website: ModiGuard

• Glass Wall Systems: It provides advanced glazing solutions including Low-E Glass for commercial and residential buildings.

Website: Glass Wall Systems

Sources:

Amirkhani S., Bahadori-Jahromi A. et al (2019). Impact of Low-E Window Films on Energy Consumption and CO2 Emissions of an Existing UK Hotel Building. Sustainability 2019, 11(16), 4265

Sorooshnia E, Rashidi M. et al. A novel approach for optimized design of low-E windows and visual comfort for residential spaces. Energy and Built Environment 6(1), February 2025, p. 27-42