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Energy Star Requirements for Windows

Energy Star Windows

Energy Star Requirements for Windows

While many people think that installing a window is just a simple means of looking outside and preventing rain and dust from coming into your house, technology and innovation have taken installing windows to new levels.

Windows now can actually contribute to energy saving should they meet certain criteria set by Energy Star. 

You may always contact us to learn more about this. In the meantime, let’s understand how Energy Star qualifies a window as energy efficient. 

What Is the Energy Star Program?

Energy Star is a government-backed program that aids businesses and consumers in saving money and protecting the environment through energy efficiency. 

You can find the Energy Star labels on many products. Such products behave almost identically to their regular counterparts. The only difference is that they must meet the energy efficiency criteria to earn that label.

Energy Star products don’t have to be strictly electric. Any product that meets the energy-saving criteria may earn that label, and that’s what we strive to achieve in windows that we offer from Optimal Windows

What Are the Energy Star Requirements for Windows?

Here are the criteria for Energy Star Certified Windows:

1. The U-factor

The U-factor is how effective a window can be at insulating against heat transfer. This U-factor measures the amount of heat that can pass through one square meter of the glass sheet whenever there’s a temperature difference between both sides of the glass (between the inside and outside of your house). 

The lower the U-factor is, the more insulating the glass will be, which translates into better heat retention in winter inside your house, and prevention of heat entry into your house in summer.

There should be a minimum U-factor for the glass depending on the climate zone. Northern zones typically require U-factors of 0.27 or below, while southern zones are okay with 0.40 or less.

2. The Solar Heat Gain Coefficient or (SHGC)

Much like the U-factor, the SHGC controls the heat inside your house. However, it does so through a different approach.

The SHGC quantifies the amount of solar radiation/heat that the windows allow to enter your home. This coefficient has a value between 0-1. The closer we are to 0, the more radiation the window will block.

For example, a window with a 0 SHGC is essentially a completely opaque window, blocking all heat (and light) from entering your home.

Alternatively, a 1 SHGC window will allow all solar heat to pass; a completely transparent window without any shading. 

Such a window would be useful in winter, as it’ll allow radiation heat to warm up your house on those frosty days, which is why windows in the northern states tend to be away from 0.

On the other hand, southern states that are close to the equator should have a good degree of opacity or shading to reduce the incoming heat. In other words, they’re closer to 0.

3. Frame Materials

Window frames can be made from various materials. However, not all of them are considered a standard by Energy Star.

For a window frame material to earn the label, it must be made of  vinyl, or fiberglass, or aluminum.

4. Visible Transmittance 

Visible transmittance, or VT, is a measurement of how much visible light can pass through the glass of your window, and it’s given a range from 0 to 1. 

The closer the value is to 1, the more natural light can enter the building through the window, which is more suitable for homes because it reduces the need for natural light.

Higher values are also more desirable when your windows are looking at a beautiful scene that you don’t want to miss. 

Alternatively, lower values mean that less visible light will pass through the window, which is useful in situations where privacy is a concern or if you need some glare control. However, you will need more artificial lighting to provide indoor illumination. 

It’s worth noting that Energy Star doesn’t have specific VT requirements. To get the Energy Star label, your window must be in the range between 0.2 and 0.8 depending on the area and the light requirements

5. Condensation Resistance

The condensation resistance is how well your window will resist water buildup. It’s indicated by a score that ranges from 0-100. The higher the score, the more your window will resist water buildup.

Regardless of the climate zone you are in, it’s important to have a high condensation resistance value, as water leaking into your house can be extremely damaging, especially if left stagnant for a long time.

Energy Star windows should have a condensation resistance value of at least 50. 

6. Certification

Another requirement to get the Energy Star label is certification.

The windows must be tested and certified by an accredited third party to ensure a bias-free decision that the windows meet the program’s criteria. 

7. Air Leakage

Air leakage is how much indoor air is exchanged with the outside air in an hour when the air pressure is 50 pascals. It’s measured using the units ACH50 or (Air Changes per Hour at 50 pascals).

Windows air leakage is given a value between 1-10. The higher the value, the more air exchange between the inside and the outside of your house.

Much like the U-factor and the (SHGC), the air leakage value requirement will differ depending on the climate zone.

For example, northern states would need ACH50 of 3.0 or less to reduce air exchange and keep the insides of the house warm. Alternatively, southern states need more air exchange to prevent heat build-up at home, which is why the acceptable ACH50 value there could go up to 6.0

8. Label Presence

Last but not least, all Energy Star-certified windows should have the labels somewhere on their frames.

If you’re provided with a window with claims that it’s Energy Star certified but you can’t see the label, you must request labeled windows. 

Optimal Windows: How Do We Fit Here?

All of our windows meet every single one of the requirements mentioned above. So, you can rest assured that you’re getting the best quality Energy Star-certified windows.

Not only do we optimize your home for maximum efficiency, but we also provide the best quality materials and the latest custom designs.

The Verdict

Energy Star-certified windows should meet all the requirements we mentioned in this post, and that’s why our Certified FGIA Master Installer Company stands unique among its competitors.

If you want the sweet spot between modern windows and energy efficiency for your home, don’t hesitate to reach out to us for a free quote

You may also call or text us at 972.768.1999, or mail us at 5760 Legacy Dr b3366, Plano, TX 75024.

Also, send an email to if you have any questions. Learn about the Energy Star program’s requirements for certifying energy-efficient windows and how Optimal Windows meets these criteria. Get the best quality Energy Star-certified windows for your home

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