Low-E glass, or low-E insulation, is designed to help regulate the home's interior temperatures without blocking daylight. This type of glass still allows most of the visible light spectrum to pass through the window, keeping your home light-filled. However, low-E glass coatings are able to protect your home from ultraviolet rays and infrared radiation that will heat up your home.
What Exactly Is Low-E Glass?
Low-E insulation is a microscopically thin, transparent film cover that reflects the light of the sun, helping to insulate and regulate to the home's interior. While early versions were often mirror-like or tinted, modern low-E glass is designed to allow most visible light to pass through and doesn't appear any different than ordinary glass.
Low-emissivity coatings are built to reflect UV light. Low-E glass reduces the amount of ultraviolet light that enters your home without blocking visible light, minimizing summer air conditioning costs while also insulating the house in winter.
Remaining heat from the sun's light is often further minimized by multi-pane, gas-filled glass that reduce the convection of air between window panes. When combined with other modern energy efficient additions, low-e insulation has the power to protect furniture and regulate interior temperatures, making your home more comfortable.
Windows with low-E glass can help keep your home's interior cool or snug. | © CC BY-SA 2.0 flickr.com / David Reber
Energy Efficient Low-E Insulation
Standard clear glass has an emittance of 0.84 over the long-wave portion of the light spectrum. This means that 84% of the light radiation hitting the glass surface is absorbed by the window, while only 16% is reflected. By contrast, low-E glass can have an emittance as low as 0.04. This low-E coating emits only 4% of its energy, and as a result actually reflects 96% of the long-wave radiation that hits the window. However, not all low-E glass is equal, and it's important that homeowners take their time shopping and comparing products before purchasing low-E insulation.
Some window manufacturers' information might not include the emittance ratings for their low-E glass. Instead, the overall effect of the low-E insulation is included in the calculation of the window's U-factor. A lower U-factor number correlates to less heat transfer and more low-E insulation. Also be sure to check the window's seasonal U-value ratings, as well as its solar heat gain coefficient (SGHC). The lower these values are, the more the window will insulate your home.
Finally, to maximize low-E insulation in warmer regions and climates, low-E coating should be added to the outside of window panes to keep the sun’s heat outside the home. In colder climates, low-E insulation should be applied to the inside of the glass to keep heat from escaping the interior, which will keep your home snug.
Low-E Insulation Glass: Offering Benefits All Around
Windows treated with low-E glass coatings reduce energy consumption, limit sun bleaching for your interior furniture and furnishings, and generally boost the overall comfort of the home. By adding low-E insulation to your windows, you can increase your home's energy efficiency and save on energy bills each month.