Solar Heat Gain: What Is It and Why Should We Care?

So what exactly is solar heat gain, and why should you care? We already know that the sun emits harmful UV rays, but did you know that the sun’s heat can raise or lower your energy bills?

First, let’s define what solar heat gain is. According to the U.S. Department of Energy (DOE), solar heat gain coefficient (aka Solar Heat Gain or SHGC) refers to the amount of heat that enters a building or space from the sun through windows, doors, or other transparent surfaces.

It is a significant factor in the overall energy efficiency and thermal performance of a building. When sunlight passes through windows or other openings, it brings in solar radiation, which consists of visible light, ultraviolet (UV) rays, and infrared (IR) radiation. The solar heat gain is primarily attributed to infrared radiation, which carries heat energy.

Solar heat gain is measured using the Solar Heat Gain Coefficient (SHGC), which represents the fraction of solar radiation that enters through a window or a surface. It ranges from 0 to 1, with lower SHGC indicating less heat transmission and better heat insulation.

So why is this so important? Let’s think about it this way: your home is like an oven. The more heat it gains, the hotter it gets. The amount of solar heat gain depends on various factors, including the orientation of the building, window size and type, shading devices such as awnings or blinds, and the properties of the glass, such as its solar control coatings or tint. 

Controlling solar heat gain is crucial for maintaining comfortable indoor temperatures and reducing the reliance on air conditioning or cooling systems, especially in hot climates. It can be achieved through several strategies, such as:

• Shading: External shading devices like awnings, shades, or louvers block or redirect sunlight away from windows.
• Window treatments: Utilizing interior shading devices like blinds, curtains, or solar films to limit the amount of sunlight entering the space.
• Low-emissivity (low-e) coatings: Applying special coatings to windows that help reduce the amount of infrared heat radiation while allowing visible light to pass through.
• Window orientation and design: Optimizing the building's design and window placement to maximize or minimize solar heat gain based on the specific climate conditions.

Choosing the suitable fabric is essential if you install a shade structure like an awning. The kind of fabric you use can affect solar heat gain. In fact, according to the DOE, using opaque and tightly woven textiles help reflect more sunlight, reducing solar heat gain.

Herculite Inc.’s shade structure textiles are designed to shade your home and help reduce solar heat gain. The type of specialty fabric used in constructing awnings and patio covers matters. Using something not designed to withstand the elements can cost you in the long run and may not reduce solar heat gain efficiently.

When choosing an awning or other shade structure, ask your manufacturer about the fabric used. Remember, you want to use something like Herculite’s awning fabrics which are:

• Fire Resistant
• Water Proof
• Heat Sealable
• Stain and Mildew Resistant
• Dimensionally Stable
• Scratch Resistant
• Feature a manufacturer's warranty
• American Standard 62" Width
• Engineered in America

According to the DOE, awnings can reduce solar heat gain in the summer by up to 65% on south-facing windows and 77% on west-facing windows. That’s much heat! So remember, to reduce SHGC, you need to be conscientious about the type of windows, shade structures, and skylights you install. If in doubt, look at the label on your ENERGY STAR® certified product; it will tell you the energy performance rating of what you’re about to buy.

Now that you know how awnings can reduce solar heat gain in the summer, download our free guide, "Five Factors to Consider when Determining Awning Quality."