The Science of Solar Gain and Glare Control in Window Design: Evaluating Spectrally Selective Coatings, Dynamic Shading Systems, and Prismatic Films

As the world finally moves to more energy efficient windows, some of the main factors of window design that are taken into consideration are “solar gain” and “solar glare.” Improvements in these two areas, specifically, help to make sure that your windows reduce heat transfer and improve visibility, creating windows that won’t affect your home’s comfort level and make it easier to enjoy the outdoor view.

What is Solar Gain?

Solar gain is the measurable amount of heat that enters into a building due to direct and indirect solar radiation. It is, essentially, how much the sun warms your property. Here in the Sacramento region, where the sun is always shining in the summer and temperatures reach over 100 degrees, windows with a high solar gain are more likely to heat up a home. Windows with a low solar gain help protect the home’s internal temperature.

What is Solar Glare?

Solar glare is how much of the sun’s brightness passes through the glass. Now, when we install windows, we want crystal clear clarity. But we do not want the “glare” of the sun – the excessive brightness that can lead to eye pain and discomfort. Many windows now have ways of reducing solar glare, which results in indoor brightness that will not hurt your eyes.

Note: Solar Gain and Glare Are Not All Related to the Windows

Many windows now have a science to them that reduces solar glare and gain. But some of those factors are not entirely controlled by the window itself. The angle of the window, its orientation, etc. can affect solar gain and solar glare. We can discuss this at your estimate.

Introducing: The New Science of Windows

Many people ask why windows are so expensive since glass is cheap. One of the reasons for this is that there is a considerable amount of science that goes into modern windows, and we can see that in the scientific improvements that have helped reduce solar gain and solar glare. Examples of this technology include:

• Spectrally Selective Coatings
• Dynamic Shading Systems
• Prismatic Films

Different windows use different systems to help reduce solar gain and solar glare. We’ll explore some of these options below.

Spectrally Selective Coatings

Windows have glazing on the exterior of the window. Spectrally Selective Coatings are coatings that go into the window glassing that are engineered specifically to reflect, rather than absorb, very specific wavelengths of light. These include “infrared” wavelengths, which are wavelengths that are not as visible to the naked eye but cause a lot of heating of the inside of the property.

Reflecting these wavelengths essentially block them by reflecting them back outdoors. Visible light that our eyes can see still come indoors, which allows us to see outside without that same light heating up our properties. Spectrally selective coatings have been evaluated for factors such as:

• Visible Light Transmittance – How much light passes through the window.
• Solar Heat Gain Coefficient (SHGC) – The measurement of how much solar heat enters a building.
• Shading Coefficient – How much the window prevents heat gain compared to a clear window.

That SHGC rating is the one that you’ll see most often with windows. It is the rating that has the greatest effect on your property’s energy efficiency, improving both your comfort in your property and how often you have to run your AC (and spend money on your energy bills).

Dynamic Shading Systems

Dynamic shading is not yet available for most window manufacturers, and it may be a few years until this is available to consumers, but the science behind it shows that these “Smart Windows” are sound. You may recall “Transitions Lenses,” which are glasses that start to tint when a person is in the sun. Dynamic shading systems work a similar way.

There are different dynamic shading systems currently being studied, but the core idea behind them is the same. Something triggers the window to start to tint when there is too much warmth or light that is trying to get through. What triggers this adjustment may vary – it may be light, it may be heat, and it may be electric voltage (smart glass), but once it is triggered, the window responds by letting in less light and heat.

Dynamic shading is an exciting new science for reducing solar glare and gain. It is not easy to obtain yet, with only a few manufacturers attempting to create it, but it is likely to become a major part of window manufacturing in the future.

Prismatic Films

Prismatic films are another window addition that are not currently added to windows directly from the manufacturer but can be purchased to reduce solar glare and gain. Prismatic films are films that cause light refraction and diffusion. They essentially manipulate light, blocking and scattering light in a way that can be beautiful but does prevent you from seeing the outdoors.

Prismatic films have been popular on TikTok and other social media sites, because they can – depending on the film – create beautiful rainbow effects around a property. They cause a drastic reduction in both glare and solar gain as well. They are useful for windows where you want natural light, but there is no view outside that you’re missing if you block the window, so you instead prefer to switch to something a bit more visually interesting that also offers privacy.

Choosing the Right Solar Gain or Solar Glare Control Systems

Every manufacturer uses different tools to prevent solar gain and solar glare. Spectrally selective coatings are by far the most common by window manufacturers – for example, Andersen, Simonton, and Milgard all use this type of coating to reduce gain and glare – but window scientists continue to evaluate and integrate new ways to block heat and excessively bright light so that you can be more comfortable in your home and reduce your energy consumption, saving money on your energy bills.

Learn more about our windows at Cal Energy by contacting our sales team, today.