New windows can be a significant investment in any home, but this is often offset by the reduction in energy bills that may be realized when switching to windows that boast a high energy efficiency.
When it comes to energy-efficient windows, homeowners should consider the benefits of Low-E glass.
What Is Low-E Glass?
Low-E glass, or low-emissivity glass, is a rating for glass that has been coated with a special substance that makes it more energy efficient. Although it was originally designed to help retain infrared light in colder climates, it is now considered the gold standard for energy-efficient homes and can be found in all regions.
Low-E glass features a non-toxic colorless coating that is thinner than a strand of human hair. This coating minimizes the amount of ultraviolet light that can pass through it, thereby improving the lighting of a room while keeping a home’s overall cooling and heating costs down.
Types of Low-E Coatings
Outlined below are the two main types of low-E coatings currently available:
- Passive Low-E Coatings – Also known as hard coat low-E glass, these coatings are made with a pyrolytic process and are applied to glass ribbon during its production on the float line. This allows the coating to fuse to the surface of the hot glass to create a strong and durable bond.
- Solar Control Low-E Coatings – Also known as soft coat low-E glass, these solar control coatings are made using a process known as magnetron sputtering vapor deposition. The coating is applied to precut glass within a vacuum chamber at room temperature. This type of coating is the highest-performing variety as it offers superior solar control performance and lower emissivity.
Those living in very cold climates can consider hard coat low-E glass thanks to its ability to allow some of the sun’s infrared energy to pass through the glass and heat the home in the winter. However, for most homes, soft coat low-E glass is ideal thanks to its superior UV protection and overall better U-value.
How Does A Low-E Rated Glass Window Work?
The application of microscopic layers of the reflective coating on low-E glass enables the windows to keep heat in during the colder winter months while allowing heat to bounce off in the hotter months of summer.
In some ways, it can be likened to the lining inside of a thermos container. When warm items are placed inside the container, heat bounces off the lining and reflects back inside the container itself to ensure its contents remain warm. This is what happens to the heat inside of a home in the cooler months with low-E glass.
The opposite situation occurs when cold items are placed inside a thermos as heat is unable to penetrate through the lining. Likewise, outside heat bounces or reflects off of low-E glass windows in summer, which keeps the home cooler and lowers your overall cooling expenses.
Are Low-E Glass Windows a Good Investment?
Low-E glass windows do carry a slightly higher price tag than regular glass windows. However, depending on where you live, they are often well worth the additional expense.
Not only do they give homeowners the look of new windows, but they come with the additional benefit of lowering energy costs. In some cases, depending on the energy efficiency of the previous windows, the difference in energy bills can be dramatic.
These windows do not usually cost significantly more than regular glass windows, which means they can pay for themselves rather quickly, especially when you consider the fact that Energy.gov reports that 25 to 30% of a home’s heating and cooling use can be attributed to heat gain and loss through windows.
These windows are a particularly good investment for those who live in colder climates thanks to their ability to prevent heat from escaping. However, they are equally useful to those in warm southern climates thanks to their ability to block heat from entering the home. In other words, they are generally a good investment for homes regardless of where they are situated.
Other Factors to Consider With Low-E Rated Glass Windows
Although low-E glass windows are always an energy-efficient choice, there are some other characteristics you may also want to look out for when shopping for energy-efficient windows.
- U-Factor – This is the rate at which the window will transmit non-solar heat flow. Lower figures are better and indicate greater energy efficiency.
Solar Heat Gain Coefficient – This is the fraction of solar radiation that is able to pass through a window either directly or via absorption and released as heat inside the home.
- Air leakage – This refers to the rate of air movement around the windows in the presence of a specific pressure difference; windows with low air leakage ratings are tighter than those with higher leakage ratings.