What Is Solar Heat Gain Coefficient and Why Does It Matter?

February 3, 2020


Energy Efficiency

Solar Heat Gain Coefficient - Clera Windows + Doors

Does your home get unbearably hot in the summer but uncomfortably cold during winter? Do you constantly find yourself dealing with skyrocketing energy bills due to excessive heating and air conditioning use? When was the last time you had replacement vinyl windows?

We think it’s about time you consider updating your old windows. In this case, putting in a little effort to understand the solar heat gain coefficient or SHGC ratings when shopping for new windows can be a total game-changer.

In this article, we’ll discuss everything you need to know about SHGC ratings, including:

  • An overview of window energy efficiency
  • SHGC’s role in energy efficiency
  • What’s the difference between shading coefficient (SC) and solar heat gain coefficient (SHGC)
  • When to choose a high or low SHGC window rating

Let’s begin!

What Is Solar Heat Gain Coefficient - Clera Windows + Doors

An Overview of Energy Efficient Windows

Before we talk about solar heat gain coefficient, let’s quickly go over what energy efficiency means for modern windows.

Basically, energy-efficient windows are those that are designed to prevent heat gain and heat loss. Heat gain and heat loss can happen in a number of ways, such as:

  • Solar radiation penetrating through the window glass,
  • Heat transfer through the window’s glass,
  • Air leakage around the windows,
  • And thermal radiation.

By preventing heat loss and heat gain, energy-efficient windows will not only allow you to have a more comfortable home but will also allow you to save on heating and cooling costs.

The energy efficiency of a window can be ascertained by looking for the Energy Star Icon which appears on the NFRC or CSA label. The solar heat gain coefficient is one of a number of other energy performance metrics to look out for when buying new windows. Other metrics include:

  • The U-factor
  • Visible transmittance (VT)
  • Air leakage, and
  • Energy rating.

Though not all of these metrics appear on both the NFRC and CSA labels, SHGC appears on both labels, thereby showing how vital this energy-efficiency metric is.

What Is Solar Heat Gain Coefficient?

The SHGC rating represents the fraction of solar radiation that can be transmitted through or is absorbed by the window. This gives you an idea of the window’s performance in terms of how much solar heat and sunlight will be released inside your home.

Basically, lower SHGC glass ratings mean a window has less solar heat gain as well as better shading capability. Whether it’s best to choose a lower or higher SHGC depends on the climate of where you live, as we will discuss further in a later section.

Every Clera Window meets the strict technical requirements of ENERGY STAR®, resulting in big energy savings, and a small ecological footprint.

An infographic detailing the importance of SHGC for windows

Is Shading Coefficient the Same as SHGC?

Previously, the industry used the shading coefficient (SC) as a measure but has since transitioned from SC to SHGC. Despite their similarities in concept, the two are different.

The SHGC rating indicates the capability of the entire window, meaning the glass and frame, to resist the heat and light from solar radiation. Meanwhile, the SC rating only calculates the heat gain from the glass portion of the glazing treatment of the window, excluding the frame.

Why Is SHGC Important?

The solar heat gain coefficient can provide homeowners with the knowledge of how a specific vinyl window replacement will behave in different seasons, climates, and locations. As a result, you can also expect to reap the following benefits.

  • A Cozy and Comfortable Home All Year Round - The SHGC can help you make excellent decisions in selecting the most appropriate type of windows for each room in your home, and therefore, prevent overheating during the summer and freezing temperatures in long winter months.
  • Protection From Harmful UV Rays - Despite the sun’s countless health benefits, there’s no denying that prolonged exposure to it also comes with negative side effects. Windows without proper glazing and suboptimal SHGC ratings can put you at risk of sunburn, premature skin ageing, and skin cancer. In addition, your furniture can also fade 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 advantage, you’ll be able to optimize your home’s overall energy efficiency and cut back your energy consumption as well as your utility bills effectively.
Why Is Shgc Important - Clera Windows + Doors

What Is the Best Solar Heat Gain Coefficient for Windows?

In general, SHGC ratings for windows could be anywhere from 0 to 1, with 0.25 to 0.80 as the most common ratings for residential windows. To find out if you need lower or higher SHGC ratings for your windows, you need to consider the climate of your region and/or the window’s placement.

When You Should Choose a Window with Low SHGC Rating?

If you live in a region that enjoys a warmer climate and requires the use of air-conditioning for the most part of the year, utilizing windows and skylights with SHGC rating lower than 0.30 are highly recommended. These windows will work best when positioned in south-facing and/or west-facing rooms areas or walls of the house, which get a full blast of the afternoon sun and which can get intense in summer.

When Is a High SHGC Rating a Good Thing?

If you live in 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 getting windows with a high SHGC rating of 0.40 to 0.60 would work for your benefit. Having them installed in your south-facing windows can provide a great source of passive solar heating.

Why Choose Clera Windows + Doors

To ensure that you get high-quality windows optimized for energy efficiency, Natural Resources Canada strongly recommends buying ENERGY STAR® windows, which guarantees that the products have been tested and certified for overall efficiency. However, all these product benefits will be in vain if your replacement vinyl windows are poorly installed, causing condensation, cold drafts, and even water leaks.

At Clera Windows + Doors, our team of experts provides a thorough assessment of your home and recommendations for SHGC ratings and energy-efficient windows tailormade to meet your needs and expectations. We have an extensive collection of stylish, ENERGY STAR® windows built to last you a lifetime. Our installation team is also fully Window Wise trained, certified, and bonded.

To know more about our solar heat gain coefficient (SHGC) ratings and our full range of services, don’t hesitate to contact us today!

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