Low-E Coatings, What Are They?

In this article, I want to discuss Low-e coatings and some common questions about windows that are designed for high-efficiency and energy savings. Not all double pane windows fall into the category of being energy efficient. Just because you have two panes of glass does not automatically ensure an energy-efficient window or door.

There are two main ingredients that a double-pane window or door will include if it is going to maximize its performance for energy savings and creating a comfortable home. These two ingredients are Low-e coatings and Argon gas. This will stay focused on Low-E, we’ll cover Argon gas in another article.

Please continue to read this article so you can learn what Low-e is and whether or not you should include it in your window or door options.

The Dirty Little Secret About Window Glass

I will let you in on a secret that will truly help you better understand your options for purchasing the right glass for your windows and doors. In the USA there are about 1,800 window companies in existence. However, there are only four main glass manufacturers in the USA. All 1,800 window companies are buying their glass from one of the big four. Just like car makers do not make tires, they buy them, window companies do not make glass, they buy it.

Of the big four glass companies, the best of the bunch for residential products is Cardinal glass. Cardinal makes the best-looking glass with the best energy performing coatings in the industry. Cardinal glass is featured in the most top of the line products like Andersen, Pella, Windsor, Marvin, Milgard, Fleetwood, Amsco, etc. In fact, we sell 20 brands of windows and doors and all of these brands use Cardinal glass in their products.

Different window companies call the Cardinal glass different names so that you are led to believe that their glass is the best and when you do a search for their glass package all you can find on a search is their brand name. When Andersen tells you that they have the best glass in the USA they are not lying. They are just not telling you that so does Pella, Marvin, Windsor, etc.

Just like I mentioned about cars buying their tires, you can get a Pirelli tire on a Chevy Impala or a Rolls Royce. The same is true with glass. You can get Cardinal glass on a $500 window or a $5,000 window. So the secret to getting a great window is to make sure it is made using Cardinal glass. If you do that, half of the work of selecting a window is done.

Low-e Coatings reject heat and keep your home cool.

What exactly are Low-e Coatings and do I need them?

Low-e stands for Low-emissivity. Here is the definition of emissivity:

The relative power of a surface to emit heat by radiation: the ratio of the radiant energy emitted by a surface to that emitted by a blackbody at the same temperature.

In other words, how well does a surface reject heat? (In simple terms). In the world of windows and doors, the question we want to ask is “How well will this window or door work in rejecting the heat from the sun from entering my home?”

In an effort to make windows and doors more efficient, scientists have developed a coating that can be applied to the surface of glass that helps it reject heat from the outside of your home and thereby keep your home cooler in the summer. This coating is called Low-E because it rejects the heat from the sun.

Low-e coatings are actually a very thin layer of silver that is “sputtered” onto the glass during the manufacturing process. Cardinal glass offers Low-e coatings in two options for most applications. They offer two layers of Low-E for most of the country or three layers for really hot climates. In Houston, the gold standard for Low-E is the three-coat option from Cardinal glass. (Cardinal Low-E 366).

The compromise when using Low-E coatings is that every layer of Low-E also reduces the amount of light that can pass through the window. In other words, the more efficient the window is the less light can pass through into your home. It is important to choose a balance of energy efficiency and still maximize the amount of light that enters the home. This can be tricky; which is why you should talk to a window expert.

Low-E Coatings By The Numbers

When you see an energy sticker on your window, it will tell you what the SHGC of that particular window is. SHGC stands for Solar Heat Gain Coefficient. The lower the number the better performing the window is against the penetration of heat. A window in the .25 or lower range is an outstanding window when it comes to heat rejection. In fact, the SHGC number actually represents what percentage of heat is allowed to pass through; .25 SHGC equals 25% of heat pass through.

When it comes to Cardinal Glass options, they offer two main products:

Low-E 366
Low-E 270

The first number (3) tells you how many coats of Low-E are on the glass, the second two numbers (66) tell you the percentage of light that is allowed to pass through the glass. With Cardinal Low-E 366, you will get 3 layers of Low-E and 66% of the light will still make its way into your home.

With the Cardinal Low-E 270, you will get 2 coats of Low-E and 70% of the light will pass through into your home. See how this works? The more efficient the window, the less amount of light will pass through the window or door.

Cardinal Glass Low-e Coatings. 366 270

Which Low-E Coating Is Best For My Windows?

So based on my experience, I would suggest you ALWAYS use Cardinal glass for its clarity, efficiency and good looks. If you live in a southern area of the country where you get a lot of direct sunlight then I would suggest the Cardinal Low-E 366. However, even if you live in a southern climate, if you have a lot of shade then I would suggest you consider the Cardinal Low-E 270 instead because you do not have direct exposure to the sun in this case. For instance, there have been times where we used Low-E 270 on most of the home but Low-E 366 on the west wall where they got a lot more sun exposure. As long as you do not mix both types on the same wall you should be ok. I would suggest you watch the video I made on this subject because it will help you see how the two options perform in direct sunlight and it will also allow you to see how the glass compares between the Low-E options.

Get Free Expert Advice

Since buying windows and selecting the best glass option for your home can be a complicated matter, we suggest that you take a few minutes to consult with a product specialist regarding your options. You are welcome to drop by our beautiful showroom at 467

W 38th Street in Houston, TX or you can call us and we can set up a time to have one of our Product Specialists come to your home for a free evaluation of the best options for your needs.

With 20 brands to choose from, we have solutions for nearly every project and budget. Please call us or complete the contact form on this page to learn more about our products and services.

We are the Houston Window Experts! Contact us today for a Free Consultation on how we can help with your window needs. You may also call us directly by dialing 832-900-7024.

Our Services include: Replacement Windows Houston, TX metro area. Houston Window Experts is a privately owned and operated company in Houston TX. For more information about us, please write to info [at] or call our Houston office at (832)900-7024. All material is copyright of Houston Window Experts. Houston, TX.