Low-E glass, or low-emissivity glass, is a type of energy-efficient glass designed to prevent heat escaping through your windows to the cold outdoors. It uses a virtually invisible coating of metal oxide on one of the internal panes of glass – next to the gap filled with inert gas – to keep the heat in.
Here’s how it works:
- Heat Reflection: The thin coating on the Low-E glass reflects back a significant portion of the heat generated inside the room back into the space, keeping it warmer.
- Solar Gain: Low-E glass allows the sun’s energy to pass through the glass from outside and get absorbed into the room, creating what’s known as passive solar heat gain.
- UV and Infrared Blocking: The coating also helps in blocking harmful UV rays and infrared light. UV can cause fading in fabrics and furnishings, while excessive infrared can add unwanted heat to a space.
- Types of Low-E Coatings: There are two main types of Low-E coatings:
- Hard-Coat Low-E (or Pyrolytic coating): This coating is applied while the glass is still in a semi-molten state. It’s more durable and less susceptible to damage, but it is less effective in terms of insulation compared to the soft-coat.
- Soft-Coat Low-E (or Sputtered coating): This involves applying multiple layers of silver between layers of metal oxide in a vacuum chamber. Soft-coat Low-E provides better insulating performance but is more sensitive and prone to damage if exposed, so it is usually used in double-glazed windows.
By improving thermal insulation, Low-E glass can significantly reduce energy costs associated with heating or cooling a space, making it a popular choice for both residential and commercial buildings.
