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What is SHGC?

It is a measurement of how much heat from the sun is allowed through  a window to help compare the efficiency of windows.

Window SHGC Rating

If you have ever been shopping for windows, you may be familiar with something called the “SHGC”. The SHGC stands for solar heat gain coefficient and is numerical value between 0 and 1. This coefficient reflects how much solar radiation or heat is getting inside the home after it reaches the glass of the window. Ultimately, it tells you how well a window is at blocking the heat coming from the sun.

A lower SHGC value means that there is less solar heat transfer, or in other words, less heat from the sun is able to come through the window and into the home. Whereas a higher SHGC value signifies a larger heat transfer and therefore more heat is able to come through the windows.

The rating method by the National Fenestration Rating Council (NFRC) is for the entire window which includes the effects of the frame. On the other hand, the center-of-glass SHGC, which is used on occasion, describes the effect of just the glazing. However, the entire window SHGC is lower than glass-only SHGC, and is typically below 0.8.

SHGC can be best explained where 1 equals the maximum amount of solar heat allowed to pass through a window and 0 equals the least amount allowed to pass through. For example, a SHGC rating of .30 basically just means that 30% of the solar heat can pass through the window. The entire window assembly is usually included in the SHGC rating and is meant to help consumers understand the energy efficiency of the glazing, window frame and any spacers.

SHGC can be measured and calculated in a few different ways. One way it can be measured is through the estimation of different simulation models. It can also be measured by recording the total heat flow through a window with a calorimeter chamber. Either way, the NFRC has standards that outline the approach for the test procedure and calculation of the SHGC.

NFRC Window Label


How Do I Find the SHGC?

Typically, you will see the SHGC ratings printed on a sticker attached to the window. The SHGC ratings on these stickers indicate that they were a part of the NFRC’s certification program, meaning they were tested and verified by professionals. The stickers given by the NFRC are to help guide consumers in buying windows that are appropriate and suited to specific applications and installation needs.

In the winter, that solar heat coming through the windows can actually provide the home with free heat. However, problems start to occur during the summer when that heat coming through the windows leads to overheating. In order to determine what the appropriate SHGC value is for your home so you are able to balance solar heat gain year round, depends mainly on the climate you live in, orientation of windows, shading, and some other factors as well.

For example, people who live in the warmer climates most likely will want a window that can keep most of the heat outside of their house all year. In this case, they would choose windows with a lower SHGC rating. However, people who live in climates that see colder weather may want windows that can let some of that solar heat in during the cooler seasons. Therefore, they would choose windows with a slightly higher SHGC rating. In fact, a higher SHGC can be beneficial if you live in a cooler climate because it can help you to save some money on heating the house during those months.

Energy Star Ratings for Windows Map


Is the SHGC Important?

In terms of the orientation of the windows, some people may be interested in getting lower SHGC windows for any of the ones that are facing west or south, so that they keep out the scorching heat from the sun in the afternoon. Ultimately, SHGC can be crucial when you are buying new windows because it can make all the difference in the world for those who are living inside the home.

There are so many reasons why it is important for a homeowner to know about SHGC and what it means in terms of their current windows and the windows they are potentially replacing.

One reason is because it determines the amount of heat that is being let in which then affects the overall temperature of your house. In addition to that, it also can affect how much power you will use. If you have windows with a lower SHGC, the air conditioner in your home has no issues working toward its desired temperature. Although, if you have windows with a higher SHGC, and more heat is getting into your house, you are forcing your air conditioner to work in double time. It is required to use more power in order to keep your home cool and this eventually leads to an expensive electric bill in the near future.

Another reason why it is important to know what the SHGC is because a lot of times people overlook the serious destruction and harm that UV rays can cause when they come through the windows. When windows have a higher SHGC rating, it not only allows more heat to come into your home, but it also allows more UV rays to flood in as well. When more UV rays are shining through the window and into the home, it can eventually fade and damage the walls, furniture, and floors.

In general, if you are looking for windows that are energy efficient and will lower your air conditioning costs, you will typically want to look for a SHGC rating of .25 or less. However, if you like allowing that natural solar heat from the sun coming into your house, you should look for a SHGC rating of .35 to .60.

Overall, when you are out shopping for replacement windows, you should not only take into account the climate you live in and the orientation of the windows in your house, but also your own personal preferences when it comes to SHGC.

The Window Hound’s Take

Efficiency and comfort are extremely important when it comes to replacement windows for your home.  Luckily, standards exist that allow you to compare windows.  But in the case of SHGC ratings, compromise is the name of the game.

One of the biggest challeneges when it comes to the SHGC rating is in climates that have frigid winters and warm summers.  In the Arizona desert, for example, you want the lowest possible possible SHGC rating.  In Wisconsin, where in the winter you welcome any heat you can get six months a year but need to feel a cool breeze another few months a year, you need to compromise.

In the map of the United States above you can see what the Energy Star requirements are for the SHGC rating for the windows in each climate zone.  Most of them in the north are designed to let more heat through than those in the south. 

What is even more interesting is how the Energy Star requirements for the SHGC ratings in northern climates change in relation to the U-factor.  Basically a less effficent window (higher U-Factor) is required to have a higher (allowing more heat in from the sun) SHGC number.  Keep in mind that the term “northern” in this map includes places as far south as the middle of Arizona.  Check out the blue area for a better idea.

Also note that the opposite is true for the remaining yellow, orange and red areas.  Presumably it is cheaper to air-condition a place than it is to heat a place for these numbers to make energy efficient sense.

But you live in one climate, so this is a guide for you to use.  You don’t need to care about what windows to choose in all of the other places.  It is just interesting to know, right?


The Window Hound

The Window Hound is helping you find the best replacement windows for your home.  Reading through pages of data, researching replacement window companies and bringing you the best information possible so that you can be a better window shopper.  The Window Hound writes for and lets us know which windows are the best for our clients.

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Low-E Coated Glass

Most quality replacement windows have some form of Low-E coating on their glass.  The quality of that coating varies, but in order be anywhere near efficient, it is a must have.

Better SHGC Rating

The amount a solar heating allowed through a window can be adjusted at the time of manufacturing of the window by using different Low-E coatings. 

In some parts of the country, you welcome the sun warming your living space.  In warmer climates, you want the sun’s warm rays to stay outside.


To most people, a window is a window.  when you go to sell your home and you inform would-be buyers of the Low-E coated windows in your home, you have now shown them that you gave your home the best care.

Let the Light In

When glass is coated with inferior Low-E coatings, it can block or blur what you see out the window.  Our Low-E coatings are visibly transparent, allowing you to see out, while preventing damaging rays in.


Our windows have three panes of glass, giving you a better window.  That also gives us more glass area to put our efficent Low-E coatings on, giving you a superior window than possible with a double pane window.

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When we created Easy Order Windows we knew we would need to offer the the best windows possible for our customers.  We would need to offer the best because we would have a hard time explaining how good a mediocre window is.  That is why we only offer superior Low-E coated, triple pane windows, at a double pane window price.

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