Low-E Glass

Low-E Glass

Low-emissivity (Low-E) glass has become an increasingly popular choice for windows and doors in modern buildings. Its ability to regulate heat and light transmission has made it a highly sought-after technology in the construction industry.

In this article, we will delve into the science behind Low-E glass, its benefits and applications, and why it is considered a sustainable and cost-effective solution.

Whether you are a homeowner, architect, or builder, understanding Low-E glass can help you make informed decisions for your next project.

Types of Low-E Glass

Low-emissivity (low-E) glass is a type of energy-efficient glass commonly used in building and construction projects. With its special properties, low-E glass has gained popularity in recent years due to its ability to reduce energy consumption and improve indoor comfort levels.

In this article, we will explore the different types of low-E glass and their unique characteristics.

1. Hard Coat Low-E Glass

Hard coat low-E glass, also known as pyrolytic low-E glass, is a type of glass that is coated with a layer of metallic oxide during the manufacturing process. This results in a hard, durable coating that is more resistant to damage and scratches. Hard coat low-E glass is typically used in exterior applications, such as windows, as it is better suited to withstand harsh weather conditions.

2. Soft Coat Low-E Glass

Soft coat low-E glass, also known as sputtered low-E glass, is made by depositing thin layers of metallic oxides onto the glass surface in a vacuum chamber. This process produces a less durable, but higher performance coating compared to hard coat low-E glass. Soft coat low-E glass is generally used for interior applications, such as double pane windows, as it provides better insulation and higher levels of energy efficiency.

3. Double Low-E Glass

A combination of hard coat and soft coat low-E glass, double low-E glass offers the benefits of both types. One pane of glass is coated with a hard coat, while the other is coated with a soft coat. This provides superior energy efficiency and durability, making it an ideal choice for both commercial and residential buildings.

4. Triple Low-E Glass

As the name suggests, triple low-E glass consists of three layers of glass with two layers of low-E coating in between. This advanced type of low-E glass is the most energy-efficient option, offering the highest level of insulation and reducing heat transfer by up to 97%. However, it is also the most expensive type of low-E glass and is usually used in high-end commercial and residential buildings.

5. Low-E Solar Control Glass

Low-E solar control glass is a type of low-E glass that is specifically designed to block out heat or solar radiation. This type of glass is commonly used in hot climates to reduce the amount of solar heat gaining into a building. It can also help to prevent fading of interior furnishings and reduce glare, making it a popular choice for commercial buildings with large windows and buildings in areas with high sun exposure.

Measurement of Low E Glass

Low E glass, also known as low emissivity glass, is a type of glass that has a low thermal emissivity. This means that it does not allow heat to pass through easily, resulting in better insulation and energy efficiency for buildings.

As a civil engineer, it is important to understand the measurement methods and factors that affect the performance of low E glass in order to specify and design appropriate building envelopes.

The overall performance of low E glass is determined by its U-value, solar heat gain coefficient (SHGC), and visible light transmittance (VLT). U-value is a measure of the amount of heat that is transferred through the glass. The lower the U-value, the better the insulation performance of the glass. SHGC is a measure of the amount of solar heat that is transmitted through the glass. A lower SHGC indicates better solar control, which is beneficial for hot climates. VLT is a measure of the amount of visible light that is transmitted through the glass. A higher VLT allows for ample natural light to enter the building, resulting in reduced energy consumption for lighting.

The efficiency of low E glass is affected by several factors, such as the type of coating, the thickness of the glass, and the type of gas used in the insulating layer.

There are two main types of low E coatings, namely hard coat and soft coat. Hard coat, also known as pyrolytic coating, is a type of coating that is applied during the manufacturing process of the glass. It is durable and compatible with double-glazed units.

On the other hand, soft coat, also known as sputtered coating, is a thin layer of metal or metallic oxide applied on the glass surface through a vacuum deposition process. Soft coat has a higher solar control performance but is susceptible to damage during transport, handling, and glazing.

To ensure accurate measurement of low E glass performance, it is important to conduct tests in accordance with industry standards such as ASTM E97, ASTM E1980, and NFRC 100. These tests include measuring the U-value, SHGC, and VLT using specialized equipment such as spectrophotometers and infrared thermometers. It is also crucial to consider the orientation of the glass and the geographic location of the building, as these factors can affect the amount of heat and light that enters the building and impact the overall performance of the low E glass.

Advantages of Low E Glass

Low E (Low Emissivity) glass is a type of energy-efficient glazing that has many advantages for buildings and their occupants. It is coated with a thin, transparent layer of metal or metallic oxide which allows it to reflect heat and block harmful UV rays.

This technology has revolutionized the construction industry and has become a popular choice for modern buildings. As a civil engineer, I have seen the following advantages of using Low E Glass in buildings.

1. Improved Energy Efficiency

One of the main advantages of Low E Glass is its ability to reduce heat loss in a building. The coating on the glass reflects the heat back into the room, keeping it warm in the winter and cool in the summer. This significantly reduces the need for heating and cooling, resulting in lower energy bills and a more sustainable building.

2. Enhanced Comfort

Low E Glass not only helps in regulating the temperature inside a building but also reduces the amount of heat that enters from outside. This creates a more comfortable and pleasant indoor environment for the occupants. Additionally, this glass also reduces glare and harmful UV rays, making it easier to work or relax indoors without any discomfort.

3. Increased Natural Light

Low E Glass is designed to allow plenty of natural light into a building while still maintaining its energy-efficient properties. This means that buildings with this type of glass require less artificial lighting, resulting in lower electricity bills and a healthier environment for the occupants.

4. Long-term Savings

Although Low E Glass may have a higher initial cost compared to traditional windows, it offers long-term savings in terms of energy bills and maintenance. The reduced need for artificial lighting and heating/cooling systems results in significant cost savings for building owners over time.

5. Better Insulation

Low E Glass offers superior insulation compared to traditional windows. It helps reduce heat loss during cold weather and keeps the heat out during hot weather, resulting in a more comfortable and consistent temperature inside the building. This also reduces the load on HVAC systems, making them more efficient and prolonging their lifespan.

6. Eco-Friendly

The energy-efficient properties of Low E Glass make it an eco-friendly option for buildings. It reduces the carbon footprint and is an excellent choice for green buildings. By using this type of glass, engineers and architects can contribute to environmental sustainability and help combat climate change.

Disadvantages of Low E Glass

As a civil engineer, I have come across various types of glass used in construction projects, one of them being low emissivity (low-E) glass. Low-E glass is a type of coated glass that has a thin metallic layer on its surface. This layer helps in reflecting heat and UV rays, making it a popular choice for energy-efficient buildings.

However, despite its benefits, low-E glass also has certain disadvantages that cannot be overlooked. In this article, I will discuss the disadvantages of low-E glass from an engineer’s perspective.

1. Higher Cost:

One of the major drawbacks of low-E glass is its higher cost compared to regular glass. The addition of a metallic coating makes it more expensive, which may not be feasible for some projects with a tight budget. Additionally, the process of applying the low-E coating involves specialized equipment and skilled labor, further adding to its overall cost.

2. Limited Color Options:

Low-E glass is available in a limited range of colors, unlike regular glass that can be tinted in various shades. This limited color option may not match the aesthetic requirements of certain projects, making low-E glass a less desirable option for architects and designers.

3. Fragility:

Another disadvantage of low-E glass is its fragility. The metallic coating on its surface is susceptible to damage during transportation and installation. Any scratches or damages to the coating can affect its ability to reflect heat and reduce its overall efficiency. Moreover, low-E glass has a lower impact resistance compared to regular glass, making it more prone to breakage.

4. Cleaning Challenges:

Cleaning low-E glass requires extra care and caution. The metallic coating on its surface is sensitive to harsh chemicals and proper cleaning techniques must be followed to avoid damaging it. This makes maintenance and cleaning of low-E glass a more time-consuming and expensive process.

5. Compatibility Issues:

Low-E glass is not compatible with certain types of glazing systems, limiting its application in some projects. For instance, it cannot be used in double or triple glazed windows, which are commonly used for better insulation in colder climates.

6. Environmental Concerns:

The production process of low-E glass involves the use of heavy metals and chemicals, which can be harmful to the environment. The disposal of low-E glass also poses a challenge as its metallic coating makes it difficult to recycle. This can lead to environmental pollution and contribute to the depletion of natural resources.


In conclusion, Low-E glass is a revolutionary type of glass that offers numerous benefits for both residential and commercial buildings. Its ability to reflect heat and block harmful UV rays makes it an energy-efficient solution that can help reduce energy costs and increase comfort levels indoors. Additionally, its high clarity and insulation properties make it a popular choice for architects and homeowners alike. With its continuous advancements and widespread use, it is clear that Low-E glass is a game-changer in the glass industry and will continue to play a crucial role in creating sustainable and comfortable environments for years to come.

FAQs about Low-E Glass

What is Low-E glass?

Low-E glass, short for low emissivity glass, is a type of energy-efficient glass used in windows and doors. It has a thin, transparent coating that reflects heat and blocks harmful UV rays, improving insulation and reducing energy consumption.

What are the types of Low-E glass?

There are several types of Low-E glass, including hard coat Low-E, soft coat Low-E, double Low-E, triple Low-E, and Low-E solar control glass. Each type has unique characteristics and is suited for specific applications.

How does Low-E glass improve energy efficiency?

Low-E glass improves energy efficiency by reflecting heat back into the room, reducing heat loss in winter and minimizing heat gain in summer. This helps maintain a comfortable indoor temperature and lowers the need for heating and cooling.

What are the advantages of Low-E glass?

The advantages of Low-E glass include improved energy efficiency, enhanced comfort, increased natural light, long-term savings, better insulation, and eco-friendliness. It contributes to lower energy bills, a more pleasant indoor environment, and environmental sustainability.

Are there different measurements for Low-E glass performance?

Yes, the performance of Low-E glass is measured using metrics such as U-value (heat transfer), solar heat gain coefficient (SHGC), and visible light transmittance (VLT). Lower U-values and SHGC indicate better insulation and solar control, while higher VLT allows more natural light.

What are the disadvantages of Low-E glass?

Disadvantages of Low-E glass include a higher cost compared to regular glass, limited color options, fragility, cleaning challenges due to sensitivity to chemicals, compatibility issues with certain glazing systems, and environmental concerns related to production and disposal.

Is Low-E glass suitable for all climates?

Low-E glass is suitable for various climates, but specific types, such as Low-E solar control glass, are designed to block out heat and are particularly useful in hot climates. The choice depends on the climate conditions and energy efficiency goals of the building.

Can Low-E glass be recycled?

The recycling of Low-E glass can be challenging due to its metallic coating. Disposal may contribute to environmental concerns, and efforts to find sustainable solutions for recycling and reusing such glass are ongoing in the industry.

How does the cost of Low-E glass compare to regular glass?

Low-E glass is generally more expensive than regular glass due to the additional coating and specialized manufacturing processes. While it has a higher upfront cost, the long-term energy savings and benefits often make it a cost-effective choice.

Is Low-E glass compatible with double or triple glazed windows?

Low-E glass is compatible with double and triple glazed windows, with specific types like double Low-E and triple Low-E designed for such applications. However, compatibility can vary, and it’s essential to choose the right type based on project requirements.

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