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5 questions to ask about replacement window glass

December 2nd, 2021 | 16 min. read

5 questions to ask about replacement window glass

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The side of a house with white stucco and a large double casement window that is black.

If you look at a window, what’s the first thing you see? There’s a high probability that you said glass.

When shopping for replacement windows, a lot of attention is put on the frame. What material do you want the window frame to be made out of? What do you want it to look like? How strong do you want the window to be? 

Even though glass makes up 95% of a window, it can easily be neglected. 

While the frame of your window determines its durability and longevity, the window glass makes up how energy efficient your window will be. 

Southwest Exteriors has been a window replacement contractor for over 30 years in San Antonio. Because of the climate we live in, we’ve always strived to provide homeowners with highly durable and energy-efficient windows to beat the Texas heat. 

We know that you need a window that will stand up against sunlight, heavy rain, hail, and snow as well. Of course, you want your window frame to protect your home, but you also need the glass to insulate your home and maintain your interior temperature. 

As you shop for replacement windows, there are some specifics you need to know to determine if your window glass will perform the way you need it to. 

This article will outline the five questions you need to get answered about replacement window glass. 

After reading, you will be equipped with the right questions to get the information you need about your replacement window glass. Then, you can choose the best window with the right glass that will perform how you need it to. 

Whether you are researching a certain window online or talking face to face with a window contractor, it is vital to get this information. 

Question #1. Who manufactures the glass? 

The first question you must answer is who manufactures the glass of the window you are looking at. With most window manufacturers, the glass is made from a separate manufacturer. 

Like with window frames and windows as a whole, there is high-quality and low-quality glass out there. 

For example, Cardinal Glass Industries is one of the leading glass manufacturers for windows. They partner with many window manufacturers to provide them with highly durable, energy-efficient glass for replacement windows. 

This is just one example of a high-quality glass that you can trust to last. Some window manufacturers also manufacture their window glass, and this can be a gamble. 

If you choose a replacement window that does not specify who makes the glass, do some digging in real homeowner reviews and how the window is rated. If you ask a contractor what windows are made of and they either do not know the answer or deter you from believing it isn’t important, this can be a red flag indicating that glass is not a high performer. 

Why is it important to ask about the glass manufacturer? 

If you’re working with a professional window replacement contractor, you always want to ask who manufactures the window and the glass. This will be the first key indicator of the quality of the glass and allow you to do your own research into the glass manufacturer and how it performs. 

Be wary if you choose a contractor that manufactures their windows and glass. Though not always the case, this type of window glass may not be as high-quality as a glass made by a specific glass manufacturer. 

Question #2. What is the Low-E coating on the glass, and how many layers are there? 

Low-E means low emissivity. This essentially means how much UV and infrared rays will pass through the window. The amount of UV and infrared rays will determine how much heat can pass through the glass and into your home. 

Now, you want your windows to have a Low-E coating on them. This is one of the most important factors that determine how energy efficient the window will be. 

Depending on your goals for your replacement windows, you want to know what Low-E coating is on the glass, the energy ratings it provides, and how many layers of the Low-E coating there are. Many windows provide the option to customize your windows with added Low-E coatings for improved energy efficiency.

Why is it important to ask about Low-E coatings? 

This is an important question to consider because the Low-E coatings are one of the first things you need to consider when outlining your goals for your new windows. 

If you want your windows to have maximum energy efficiency and block most of the UV and infrared rays that penetrate the window, you will want a window with multiple Low-E coatings. 

If you aren’t as concerned with the amount of heat that will come through your windows, you still want to know how your window glass will perform and protect your home from harmful rays. 

Question #3. Is the window gas-filled, and what is the gas in between the glass panes? 

Most multi-pane windows have a gas fill in between the panes. Argon and krypton gas are the most common types of gas used. Both types of gases have similar properties in how well they insulate. 

Gas-filled windows increase the insulating properties of the window. Compare it to when you layer up when it’s cold outside. The more layers you have, the more you are protected from the cold. 

The gas between the panes of windows is an added barrier against exterior heat and cold. This means it will keep the internal temperature of your home regulated. 

Why is asking about gas-filled panes important? 

Like Low-E coatings, knowing whether or not your windows are gas-filled will determine how energy efficient they are. 

If you want your windows to be more energy-efficient, you will want a gas-filled window and sealed properly. 

Question #4. What is the guaranteed fill rate of the glass?

Gas-filled windows have a guaranteed fill rate. This percentage measures how much gas is in the window panes. 

For example, Cardinal glass has a guaranteed fill rate of 95%. This means that 95% of the space between the window panes is filled with insulating gas. 

Why is asking about the guaranteed fill rate important? 

The higher the guaranteed fill rate of a window, the more insulating it is. If you are looking for a window with high energy-efficient properties, you will want a window with a higher guaranteed fill rate. 

It is also important to know the fill rate because some gas will leak over time. This is inevitable and something that you should factor in when considering the energy efficiency of your replacement windows and the fill of the panes. 

Question #5. How is the quality of the seal around the glass?

The last question you want to answer about the glass on replacement windows is the quality of the seal around the glass. Now, this sounds like a vague concept, so we’ll explain further what to look for in a quality window. 

The sealant used around the window glass is the first thing you want to know. Like other materials used to finish a window, like caulk and paint, you want a high-quality sealant that will last. Silicon is a popular material used for sealants, and some glass manufacturers have a two-step sealing process for added durability. 

The next thing you want to know about the seal around the glass is if a spacer bar is used around the glass. Spacer bars are usually made of aluminum or stainless steel. Steel is less conductive than aluminum, so if you are concerned about the conductivity of your window and how it will trap heat, you will want a window with a stainless steel spacer bar.  

Why is asking about the quality of the seal around the window glass important? 

The quality of the seal around the window glass must be inspected, just like the quality of the window overall. 

The seal around the glass protects the interior of your home just as the seal around the window frame does. If the glass is not sealed properly, air and water can seep around the edges. 

If the seal around the glass is not high-quality and your window is gas-filled, the gas will also leak much faster than it should. This is why you want to ensure you know how the glass around the window is sealed and what materials are used to seal it to ensure its quality. 

How to find the right window glass for your replacement windows

Now that you know five questions you should ask about replacement window glass, you can get the right information from your window contractor to ensure your replacement window will perform the way you need it to. 

If you are looking for a window with the highest performing energy efficient ratings, then you will want a gas-filled window with multiple Low-E coatings and a high-quality sealant around the glass that is made from a glass manufacturer with a reputable history of successful window glass. 

Considering the glass quality in your replacement windows should be included when considering your goals for your windows as a whole. 

If you want a high-quality window that is energy efficient and will protect your home from harmful rays, you are going to have to pay more for a window to perform how you want it. 

On the other hand, if you are looking for the least expensive window and aren’t concerned about the longevity or performance of the window, then you probably aren’t putting much thought into the glass, and that’s okay. 

It all depends on your ultimate goals for your replacement windows and how you want them to perform. 

With Southwest Exteriors, we want to help guide you to the right window solution to fit your goals. While we do offer high-performing windows with some of the best energy ratings, we know that a window with added bells and whistles is not right for everyone. 

Ultimately, we want you to be educated on what to look for to find the right replacement window for you with the glass qualities and performance ratings that will match your goals. 

After learning about what to consider to find the right glass for your replacement windows and talking around added costs, you probably wonder how much a window replacement costs in total. 

This article and video will outline the top five factors that influence the cost of a window replacement project, like window material, size, and customizations