Solar Heat Gain Coefficient

What Is Solar Heat Gain Coefficient? (It’s Importance)


In the quest for sustainability, energy efficiency in buildings has grown to be a crucial factor. The solar heat gain coefficient (SHGC) is critical in maximizing energy efficiency.

Is your home hot in the summer but uncomfortably cold during winter? Or do you constantly find yourself dealing with costly energy bills due to excessive heating and air conditioning use? Have you remembered the last time you had replacement vinyl windows? We think it’s about time you need to update your old windows.

In this case, giving in a little effort to understand the solar heat gain coefficient or we can say it SHGC ratings when shopping for new windows may be a total game-changer. In this our short journey, we’ll discuss everything you need to know about SHGC ratings, including:

  • We took overview of the energy of window efficiency
  • SHGC’s applied role in energy efficiency
  • differences between shading coefficient and SHGC
  • When we need to choose a high or low SHGC window rating

We shall examine the idea of SHGC, its significance, its connection to climates, and its comparison to similar words in this article. Let’s start!

How much solar heat gain is there?

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The solar heat gain coefficient (SHGC) governs how much solar radiation gets through a window or glazing system. It shows how much solar heat gain passes through a window and into the structure. The SHGC takes into account both direct and absorbed solar radiation that’s re-emitted as heat inside the building.

An Overview of Energy Efficient Windows

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Before we start talking about solar heat gain coefficient, let’s have a go over what energy efficiency means for modern windows. These windows are designed to safely heat gain or loss. Heat gain and heat loss can happen in a many ways, some of them are as following:

  • In Solar radiation penetrating way
  • Via the window glass,
  • Heat transfer via the window glass,
  • With Air leakage in the windows,
  • In thermal radiation

Solar Heat Gain Coefficient: Why Is It Important?

The SHGC of a window significantly influences the energy efficiency and comfort levels inside a building. Windows with a lower SHGC value send less solar heat, which can reduce the cooling load placed on air conditioners during the sweltering summer. Windows with an optimized SHGC help to reduce energy consumption, raise occupant comfort, and rely less on mechanical cooling by effectively limiting solar heat gain.

The solar heat gain coefficient, it can give homeowners knowledge of how a specific vinyl window replacement will behave in many seasons, climates, and locations. As a result, you can also expect to enjoy the following benefits:

  • A Cozy and Comfortable Home All Year Round: The SHGC can help in making excellent decisions in selecting the most appropriate type of windows for each room of your home, and therefore, prevent overheating during the summer and freezing temperatures in long winter months.
  • Protection From Harmful UV Rays: After the sun’s countless health benefits, there’s no one denying that prolonged exposure to it also comes with negative side effects. Windows that don’t have proper glazing and suboptimal SHGC ratings can put you at risk of sunburn, premature skin aging, and skin cancer. Furthermore, your furniture also fades a lot faster when exposed to harsh, direct sunlight on a daily basis.
  • Lower Energy and Heating Bills: By making the SHGC rating work for your advantages, you are easily able to optimize your home’s overall energy efficiency and cut back your energy consumption as well as your utility bills effectively. This can be a great advantage for you.

Climates and Solar Heat Gain Coefficient:

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Depending on the climate where a building is located, windows should have excellent Solar Heat Gain Coefficient (SHGC) value. In warmer climates, windows with lower Solar Heat Gain Coefficient (SHGC) values are often preferred to minimize the entry of excess heat and reduce cooling requirements. On the other hand, windows with higher SHGC ratings can be advantageous in colder areas since they permit more solar heat gain, which reduces the need for heating during the winter.

The SHGC rating shows the fraction of solar radiation that is transmitted through or is absorbed by the window. This provides you an idea of the window’s performance in terms of how much solar heat and sunlight will be offered inside your home. Basically, lower SHGC glass ratings shows that the window has less solar heat gain as well as better shading capability.

No matter what, it’s best to choose a lower or higher SHGC depending on the climate of where you used to live, as we will discuss further in another section. Every Clear Window comes with the strict technical requirements of ENERGY STAR®, resulting in big energy savings, and in a small ecological footprint.

Is the SHGC the same as the shading coefficient?

In the past, the industry used the shading coefficient (SC) as a measure but has since transitioned from SC to SHGC. Unite the similarity in concept, the two are different. The Solar Heat Gain Coefficient (SHGC) rating shows the capability of the entire window, meaning it shows the capability of glass and frame, to resist the heat and light from solar radiation. On the other hand, the SC rating only calculates the heat gain from the glass portion of the glazing treatment of the window, without the frame.

Despite their connection, the shading coefficient (SC) and SHGC are not the same. The shading coefficient only calculates the direct solar heat gain, whereas the SHGC assesses the entire solar heat gain through a window. SHGC provides a complete picture of a window’s performance by accounting for direct, absorbed/re-emitted solar heat.

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Which solar heat gain coefficient for windows is the best?

The environment, building orientation, and intended energy efficiency objectives all play a role in determining the appropriate Solar Heat Gain Coefficient (SHGC) for windows. Local building codes, energy rating programmes, or consultation with energy specialists are all options to determine the appropriate SHGC value for a given project. Generally, an SHGC value of 0.40 or lower is advised for energy-efficient designs in hot areas, whereas a value of around 0.55 may be more appropriate in cooler climes.

Generally, Solar Heat Gain Coefficient (SHGC) ratings for windows could be between 0 to 1, with 0.25 to 0.80 this is the most common rating for residential windows. To find out
What you need is for lower or higher SHGC ratings for windows, you have to consider the climate of your region and the window’s placement.

What distinguishes U-Value from SHGC?

While the U-value evaluates a window’s thermal conductivity, Solar Heat Gain Coefficient concentrates on solar heat gain. The U-value is a measure of the rate of heat transmission through a window, taking into account both conduction and air leakage. A lower U-value indicates more excellent insulation and less heat loss. When choosing energy-efficient windows, it’s crucial to consider both SHGC and U-value because they each address a separate component of a window’s performance.

What is the PF value for the solar heat gain coefficient?

There is little knowledge available concerning this particular coefficient as of 2023. However, to maintain accurate information regarding solar heat gain coefficients, staying current with the most recent research and industry standards is crucial.

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When Should You Choose a Window with Low SHGC Rating?

If you used to live in a region that enjoys a warmer climate and wants the use of air-conditioning for the most part of the year, utilizing windows and skylights with Solar Heat Gain Coefficient (SHGC) rating lower than 0.30 are highly recommended. These windows will work best when they are in south-facing and/or west-facing rooms, areas or walls of the house, which have a full blast of the afternoon sun and which can be intense in summer.

When Is a High SHGC Rating a Good Thing?

If you live in a region which has a colder, northern climate, the priority would be to maintain a warm and comfy temperature for your home without relying heavily on heating.

This is where you need to get windows with a high Solar Heat Gain Coefficient rating of 0.40 to 0.60 would work for your benefit. Having them installed in your south-facing windows will provide a great source of passive solar heating. And you are able to enjoy the seasons.


Different standards and estimations are used to compare the insulating properties of different windows and doors. These estimations are needed for designers and building owners to make informed decisions that will directly affect their energy efficiency programs and, ultimately, their bottom line.

One measure of energy that can be transferred through a building component is knowable and often drives decision-making for building design areas such as air conditioning and heating. This ultimate factor is the SHGC.


The U-factor is called the total heat transfer number. It considers radiation, conduction, and convection and that’s why encompasses all modes of heat transfer into or out of a building. U-factor, or U-value, can similarly be the R-Value for insulation when calculating the building’s overall thermal envelope.

Heat can be lost or may be gained through glass by the processes of conduction, convection, and radiation. On the other hand, SHGC is only considering the heat transfer into the building coming from solar radiation. Both U-value and SHGC go behind the model of lower values being better for insulation, with increasing the potential for energy savings, and decreasing the heat loss in a building.


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There are many ways that Solar Heat Gain Coefficient (SHGC) can be reduced, such as outside shading such as pergolas, Venetian blinds, trees, and bushes, etc. The other ways that SHGC can be reduced are Low-e coatings. Virtually invisible, low-emissivity coatings can significantly reduce the amount of solar heat that can pass through the glass. Low-e films are made by a coated polymer and are applied to the inside of a window or a door lite to block or slow incoming solar radiation transmission.

Window react

Windows react thermally by direct and indirect sunlight. Sunlight hits a window, the heat does three things.

Reflection : This is where sunlight hits a window and some of the solar heat is reflected back.

Absorption: In this case Absorption is the process of some heat being absorbed, this can be emitted outside and emitted inside.

Transmittance: This is where the remainder of the heat is transmitted by the window into the building.

A practical example

The graph provided below represents the heating and cooling demand of a home in Perth for different orientations and solar heat gain coefficients.

Different analyses can be receive from this data, here’s some to start with:

We have a heating-dominant climate.

  • Minimal energy needs are observed for the northern orientation, while for the western facade requires higher energy consumption.
  • The southern façade shows increasing heating demands due to the absence of passive heat gains much specifically on glazing with SHGC 0.2. SHGC 0.6 providing passive heat gains in the south works well to reduce heating demand.
  • When using a low SHGC glass, typically with a rating of 0.2 and likely darker in color, heating demand needs to be high across all orientations like it blocks passive solar heat gain. Furthermore it may prove beneficial on the western façade for the same reason.
  • The High SHGC 0.6, clear glass, will have the most likely result in high solar heat gains, specially on east and west orientation.

Is SHGC the same for all types of windows?

As we discussed, SHGC values serve as a starting point for energy efficiency assessments; they need to be adjusted once specific window types are confirmed. It mainly depends on the ratio of glass area to frame area.

Commonly, awning, casement, or louvre windows exhibit total system SHGC values is lower (10-15%) than fixed or sliding windows because of differences in glass and frame size. This differentiation also applies to different window types, for example single-glazing or double-glazing.

If anything, the framing area influences the total system U-value of a window, contingent on the material selected for the frame as the U-value is the thermal conductivity of the whole assembly including these two glazing and framing. For quick, an awning window equipped with an aluminum frame

, if anything results in a higher U-value due to the enlarged frame area, which can lead to better heat gain or cooling losses. But set windows cannot be put in everywhere, specially in areas that look like natural ventilation. Hence, again a right balance between the different parameters of the windows, user needs and design is necessary.

How Important is SHGC in Different Climates?

The importance of SHGC differs, as we have mentioned before, based on where it is. In a much hotter southern state like Texas or Florida, SHGC is most important, because it can be very hot, and even winters are relatively warm.

In such states like Alaska, if we look on the other side, the solar heat gain coefficient is not more important than the insulation properties such as window or door. SHGC ratings are usually now applied to windows and doors that are sold there, but you can be more interested in their R or U values.

Sunlight Transmittance

The capacity of glazing in a window, door, or skylight to Tremble sunlight into a home can be measured and rated by the following energy performance characteristics:

The fraction on the visible spectrum of sunlight is Visible transmittance (VT) which is (380 to 720 nanometers), and can be weighted by the sensitivity of a human eye, that is transmitted through the glazing of a window, door, or skylight. A product which has a higher VT transmits more visible light.

VT is shown as a number between 0 and 1. The needed VT for your window, door, or skylight should be determined by your home’s daylighting needs and/or whether you want to reduce interior glare in a space.

The LSG is the ratio between these two terms VT and SHGC. It gives a gauge of the relative efficiency of different glass or glazing types in transmitting daylight on the other hand it is blocking heat gains. The higher the number can be affected in more light transmitted without adding excessive amounts of heat. This performance of energy is not always provided.

Pros and Cons


Long-term savings with this you enjoy long term savings

Low-maintenance The maintains of Solar Heat Gain Coefficient is low

Diverse Uses it has Diverse Uses


Environmental impact of manufacturing it has a Environmental impact of manufacturing

Scarcity of materials this is one of those his disadvantages.

(FAQs)-Frequently Asked Questions

There is only one way to calculate the solar heat gain coefficient.

Strict testing following acknowledged standards, such as the National Fenestration Rating Council (NFRC) in the United States, is used to calculate the solar heat gain coefficient. Under controlled circumstances, testing entails monitoring solar radiation transfer and heat gain.

Is it possible to increase the solar heat gain coefficient?

Yes, there are several ways to increase the solar heat gain coefficient of windows, including the use of low-emissivity (Low-E) coatings, spectrally selective glazing, double or triple glazing, and the addition of shading fixtures like blinds or awnings.

Do SHGC-related building codes or regulations exist?

Numerous building regulations and energy rating systems outline the maximum permissible SHGC values for windows in various climate zones. Buildings must adhere to these guidelines to guarantee that they are energy efficient.

Can SHGC parameters change to suit specific requirements?

Depending on the requirements of a particular project, certain window manufacturers provide alternatives for tailoring SHGC values. With these options, builders, and planners can make structures with the good possible power efficiency.


Understanding the solar heat gain coefficient is essential to develop energy-efficient buildings with high-performing windows. The amount of solar heat that enters a building through windows is determined by the SHGC value, which affects both energy use and occupant comfort.

Selecting windows with an adequate SHGC for the local environment and building orientation will result in the greatest energy efficiency.

This will also lessen the need for mechanical cooling systems. To make informed choices about solar heat gain coefficients and window design, stay current on industry advancements, and speak with professionals.

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