a window with low-e coating

Learn the Differences in Low-E Coatings

Low-emissivity (Low-E) coatings on windows may not be visible to the eye, but their impact on a home’s comfort and energy efficiency is profound. Applied to glass, these microscopic coatings play a pivotal role in controlling the temperature within buildings, thereby enhancing the living environment. By reflecting interior temperatures back inside during the winter and blocking excessive heat from entering during the summer, Low-E coatings make significant strides in energy conservation. Additionally, these coatings also help filter out harmful UV rays, protecting both the health of the occupants and the longevity of the interior furnishings.

What is Low-E Coating?

Low-E, or low-emissivity, coating is a thin metallic layer applied to glass that improves the window’s insulation properties. In simpler terms, it acts much like a thermos—a barrier between outside temperatures and indoor conditions, reflecting heat back to its source. This technology hinges on the use of metals like silver or tin oxide, which are capable of reflecting heat while still allowing light to pass through. The effectiveness of Low-E coatings in reducing energy consumption is significant; they reduce the heat flow through the glass, thereby cutting down on heating and cooling costs and creating a more energy-efficient building.

Types of Low-E Coatings

Hard-Coat (Pyrolytic)

Hard-coat Low-E coatings, also known as Low-E 180, are manufactured through a process called pyrolytic coating. This involves applying the metallic oxide layer to the glass surface during the glass manufacturing process while the glass is still hot. The coating fuses to the glass, creating a strong bond that is very durable and resistant to wear. This type of coating is typically used in applications where the windows may be exposed to harsh weather conditions or where cleaning and maintenance could be abrasive. The robust nature of hard-coat Low-E glass makes it ideal for use in commercial buildings and in residential settings where more resilience is required.

Soft-Coat (Sputtered)

Soft-coat Low-E coatings, known in the industry as Low-E 270 and Low-E 366, are applied in a different manner. This type of coating is applied to the glass in a vacuum chamber, a process known as sputtering. Multiple layers of silver are deposited onto the glass, allowing for greater control over the coating’s properties. The result is a coating that has superior thermal and optical performance compared to hard-coat Low-E glasses. Because of their high efficiency in controlling heat flow and blocking UV rays while maintaining high levels of natural light, soft-coat Low-E coatings are preferred for residential applications. They are particularly effective in climates where both heating and cooling costs are a concern, providing excellent insulation against both heat loss and heat gain through windows.

Performance Differences

Thermal Insulation

Both types of Low-E coatings excel in thermal insulation but in slightly different ways. Hard-coat Low-E 180 coatings are generally more effective at retaining heat within a room, making them ideal for colder climates where interior warmth is a priority. They reflect the indoor heat back inside, reducing the need for additional heating. On the other hand, soft-coat Low-E 270 and 366 provide superior performance in minimizing heat gain from outside, which is crucial in warmer climates to keep interiors cool without overworking the air conditioning systems.

UV Protection

When it comes to UV protection, soft-coat Low-E coatings typically outperform their hard-coat counterparts. The multiple layers of silver in soft-coat Low-E 270 and 366 coatings are more efficient at blocking harmful UV rays, thereby preventing fading and damage to furniture, carpets, and draperies. Hard-coat Low-E 180 coatings also block UV rays but to a lesser extent, making them more suitable for areas where intense sunlight is less of a concern.

Visibility and Light Transmittance

Visibility and light transmittance are crucial factors for window glass. Soft-coat Low-E coatings (Low-E 270 and 366) are designed to maximize light penetration while reducing glare, offering clearer views and brighter spaces. This makes them preferred in residential settings where natural light is desired without the accompanying heat. Hard-coat Low-E 180, while still allowing significant light transmission, may slightly tint the glass, which can alter the natural color perception from the inside.

Factors Influencing Coating Choice


The choice of Low-E coating is significantly influenced by the local climate. In colder regions, a hard-coat Low-E 180 is advantageous for its heat retention properties, while in warmer regions, a soft-coat Low-E 270 or 366 is beneficial for its ability to reject solar heat.

Window Orientation

The orientation of a building’s windows also affects the choice of Low-E coating. South-facing windows, for instance, might benefit more from soft-coat Low-E coatings to prevent heat gain in sunny climates, whereas north-facing windows in cooler climates could use hard-coat Low-E to maximize heat retention.

Aesthetic Considerations

Finally, the aesthetic impact of Low-E coatings cannot be overlooked. Soft-coat Low-E glass typically offers a clearer, more neutral appearance, making it suitable for homes where aesthetics are as important as performance. Hard-coat Low-E glass can have a slight coloration, which might be considered if it complements the architectural style of the building.


Throughout this discussion on Low-E coatings, we’ve explored the differences between hard-coat and soft-coat technologies—each serving distinct purposes based on their thermal insulation capabilities, UV protection, and light transmittance qualities. Whether it’s enhancing heat retention in cooler climates with hard-coat Low-E 180, or reducing heat gain and protecting against UV rays in warmer regions with soft-coat Low-E 270 and 366, selecting the right type of Low-E coating is crucial for maximizing energy efficiency and comfort. We encourage homeowners and project managers alike to consider how these advanced technologies can be integrated into their properties to reap long-term benefits in energy savings and interior comfort.

About Vinyltek

Vinyltek has been at the forefront of window technology, providing high-quality solutions tailored to the unique needs of our clients. With our advanced Low-E coating options, Vinyltek windows not only enhance the aesthetic appeal of your home but also contribute significantly to its energy efficiency and protection against environmental elements. We invite you to explore our diverse range of products and discover how Vinyltek can transform your living or work spaces. For more personalized advice and to find the perfect window solutions for your needs, don’t hesitate to contact us. Our team of experts is ready to assist you in making informed decisions that align with your goals.