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The Lowdown on Low-E

By Gates Dearen

Courtesy of Wikimedia Commons
When it comes to windows, the glass is where the rubber meets the road, but when it comes to window panes, not all glass is equal.  Whether your windows are single-pane, double pane or triple pane, the formula used in the production of the glass and the glass coatings used in their manufacture have a direct bearing on their ability to stand up to the elements.

Caveman Tech

Glass has been around a long, long time.  Archeological evidence indicates that glass has been in existence since the Stone Age.  While cavemen didn’t have windows in their caves, it was quite common for the dead to be buried with glass beads and other glass ornaments as far back as 3,000 BC.  Since glass starts off as sand, it should come as no surprise that the first glass originated in Mesopotamia.  While the Pharaohs in Egypt weren’t able to equip their palaces with glass windows, it is known that by the time of the Roman Empire, windows were in use.

That doesn’t mean that the art of creating window panes was an easy one to master.  Roman windows didn’t look anything like what we have come to know today.  Their window glass was darker and lumpier than that used in modern times.  Still, it kept out the wind and weather.  Glass technology advanced dramatically during the second and third centuries, culminating with the stained glass that was used extensively in cathedrals.  Still, as a whole, the use of windows took a nosedive after the fall of the Roman Empire.
Courtesy of  Wikimedia Commons

It wasn’t until the 17th century that glass windows became the norm in Europe.  Before that, windows were constructed of everything from paper to flattened animal horns.  As late as the 19th century, it was common for settlers in the Wild West to employ greased paper windows to adorn their cabins.   It kept out the elements, but it sure spoiled the view.

Who Put the E in Low-E Glass?

Courtesy HomeRite
Windows and Doors
When it comes to the science of window glass, it took until the middle of the 20th century to address that.  A century before it was known that heat exchange between surfaces was characterized by their emissivity.  In the science of Thermodynamics, emissivity is defined as the ability of a surface to emit radiant energy as opposed to a black body of the same area.  In other words, emissivity is the ability of a surface to radiate energy.  Since a glass pane is nothing but surface area, this principle is key to making a home or office more energy efficient.

The bad news is that while glass is terrific at letting in light, in its base form, it is a terrible insulator.  That’s why glass windows and doors are one of the chief culprits in heat transfer and energy loss.  It wasn’t until the 1950’s that the question of low emissivity (aka Low-E) glass was first tackled by the English window manufacturer BOC Edwards, who showed that panes coated with BiOx and Gold reduced heat reflection.  Soon after that, other glass manufacturers followed suit by patenting their own Low-E window coatings. This technology became particularly important during the energy crisis of 1974 when it was proven that windows were one of the biggest heat sinks in buildings of all kinds.  This finding culminated in a number of new patents being issued in the 1980’s for silver layer coatings on flat glass for low-e application.

Modern Science Meets Modern Windows

Today’s Low-E glass windows have 200 years of scientific research to thank for their ability to reduce emissivity.  Modern Low-E windows are coated with microscopic layers of metal oxides that are invisible to the naked eye.  Their task is to admit natural light while reducing the amount of infrared radiation and UV rays.  As a result, your home stays cooler in the summer, warmer in the winter and your furnishings don’t become faded by the Sun’s rays.
Courtesy of HomeRite
Windows and Doors

While Low-E windows before the turn of the century were only intended to suppress infrared radiation, those of the 21st century are much more robust in their ability to ward off the worst that the elements can throw at them.  That’s due to the fact that coatings have come a long way during the past few years. 

Hard Coats, while less efficient, can stand up better to the elements.  As a result, they are applied to the outside of windows.  Hard coats are also applied between double-pane windows.  Most commonly found as a thin sheet, this layer is a highly efficient insulator designed to minimize heat loss.  This insulation can be further enhanced with the addition of argon gas between the panes.

Soft Coats will erode if exposed to wind and weather.  Therefore, they are relegated to the inside of window panes.  Soft coatings are highly reflective and can reduce the amount of UV radiation entering a home. 

The bottom line is that while you can’t see it with the naked eye, modern Low-E windows are definitely worth the investment.  They not only help make your home more energy efficient, they also reduce the wear and tear that the Sun can take on your furnishings.  If you want to get the lowdown on Low-E glass windows and doors, give us a call at 904-296-2515.

HomeRite is a window and door dealer that specializes in energy efficient, quality windows with warranties and service to match. The company has been in business since 2005. HomeRite has partnered with a manufacturer that has been producing high-quality products and providing excellent customer service for over 60 years. Windows and doors from HomeRite are some of the highest quality, most thermally efficient windows and doors on the market.

HomeRite products add substantial value to their clients’ properties. HomeRite is a member of the United States Green Building Council, a non-profit organization comprised of leaders across the industry working to advance environmentally responsible buildings.

Gates Dearen is the co-owner of HomeRite Windows and Doors in Jacksonville, Florida. He and Richard Walden have been serving the building products industry in Florida for over 25 years. They strive to match homeowners with the right windows and doors for their homes and budgets. They make the home improvement process pleasant with first-rate, energy-efficient products, affordable pricing, and award-winning installers who employ the best practices and who always treat customers and their property with the utmost respect.

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  1. It's amazing how windows have gone hi-tech. Now you can save money and the planet at the same time. Cool!

  2. I purchased some of their windows and it lowered my electric bill by 20 percent the first month. Now if I can get JEA to stop increasing the rate I would be golden.