Does Window Glass Block UV-Rays?

Does Window Glass Block UV-Rays?

You know how important it is to wear sunscreen before spending a day at the pool but are you also at risk for skin damage when sitting by a window? The answer isn’t a simple yes or no. It depends on the type of window (car vs. home, for example) and whether it has coatings to reflect UV rays. Keep reading to learn more about UV rays and their effect on residential windows. 

What Are UV Rays?

Sunlight contains three different types of radiation:

  • infrared radiation,
  • visible light,
  • and ultraviolet (UV) radiation.

We can feel the heat of infrared radiation and see the effects of visible light, but can’t feel or see UV rays. Over time we can see and sometimes feel the damage caused by UV rays:

  • sunburn,
  • tanned skin,
  • and skin cancer. 

Each type of radiation has a particular wavelength (and corresponding frequency and energy) that falls within a range called the electromagnetic (EM) spectrum. UV rays operate at a wavelength between 10 and 400nm, placing its radiation levels between those of visible light and x-rays on the EM spectrum.

Scientist breakdown the range of UV light into three categories including UV-A, UV-B, and UV-C. Thanks the the earth's atmosphere, UV-C light↗ does not reach the ground. However, we are regularly exposed to UV-A and UV-B light during the day, that’s why daily wear of sunscreen is recommended. But what about when we’re inside our homes? Will the UV rays pass through the window glass?

Can UV Rays Enter Through My Windows?

You know that visible light can enter through your windows, but can invisible UV rays enter? Home windows block the majority of UV-B rays↗, which are responsible for sunburns but block only about 25% of UV-A rays, which penetrate deeper into the skin to accelerate aging↗

You won’t get a sunburn from walking around or past your windows but excessive time in front of a sunny could damage your skin over time. Think of the way your arms tan lightly from driving, even with the windows up. Additionally, the sun’s rays can cause the color of your curtains, furniture, or floors to fade just like the color of your house’s siding does on the exterior.

Placing shades or blinds over your windows can help block harmful UV-A rays, but they also block visible light. Shades and blinds are helpful but they aren’t ideal. Too much exposure to UV rays can be damaging but we do need sunlight exposure. The vitamin D we get from the sun makes us feel good and keeps us healthy. If UV-A rays are a concern for you, consider treating your existing windows with a special tint or purchasing new "low-E" windows. 

Learn More: Low-E Glass Types Explained

Can Low-E Windows Protect Against UV Rays?

Low-emissivity (low-E) windows are specially treated with a thin metallic coating↗. This coating allows visible light to pass through but reflects both infrared radiation and UV rays. Low-E windows keep your home cooler in the summer by blocking the heat of infrared radiation while protecting you and the appearance of your home interior by blocking UV-A rays. This coating can also reduce the glare of sunlight, making it easier to see indoors. 

If you don't want to purchase brand-new low-E windows, you can opt to have your current windows treated with a tint or glaze. Not every type of window treatment↗ will block UV-A rays, so be sure to choose a functional rather than decorative tint. A ceramic window film is considered the most effective tint option for blocking most UV rays.

Are You at Risk?

You can make some minor changes to protect yourself from the UV-A rays that penetrate traditional windows. Avoid sitting in a chair directly in front of a sunny window, for example, or pull the blinds when you aren't using a room to prevent the sun from fading items in the room. The best way to enjoy both visible light and protection from UV radiation is to choose windows with low-E glass. If you're currently buying replacement windows for your home, ask your window dealer or contractor about your options before you choose your windows. 


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