Sunlight Barriers: Does Glass Block the Health Benefits of Sunlight? What Windows and Windshields Let Through and What They Filter Out
Voice of the Audience
"How do windshields affect this? If you have someone that drives several hours each day, does the windshield allow the good light in? I had glasses for a while that darkened when I when outside, but it didn’t work in the car while driving because the windshield blocked the light that triggered the transition. Does it block the light you are talking about here?"
YouTube comment
"I'm in Toronto Canada. I sit by the window (with sunblock on) in the am to get some 'sunlight' while I work facing the sun... had no idea I was getting so little from it. I'm going to try to get outside in the morning."
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"Does sunlight coming through a window glass, help my body receive the benefits of the sunlight"
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Behind the Answer
Sunlight is composed of various wavelengths, including Ultraviolet (UV), visible light, and Infrared (IR), with IR making up approximately 54% of solar energy. The crucial finding is that modern barriers like windows, windshields, and common eyeglasses filter out or block key beneficial wavelengths, severely limiting the physiological effects of sunlight.
Specifically, common windows and windshields often block beneficial infrared (IR) light, which is essential for stimulating mitochondrial function and producing cellular melatonin during the day. Modern energy-efficient Low-E glass is explicitly noted for filtering out beneficial infrared light. Similarly, prescription eyeglasses often automatically include features that block UV rays and sometimes blue light, which can interfere with the body's natural signaling mechanisms that require full-spectrum exposure.
This article is part of our Light Optimization series and explores how glass and modern barriers impact sunlight’s biological effects and what you can do to restore full-spectrum exposure.
Read the main Light Optimization articleThe Concern
The primary confusion and worry stem from the belief that indoor sun exposure through a window or car glass provides the full range of health benefits, especially during cold weather or long commutes. The audience is concerned that if glass blocks therapeutic wavelengths like IR and UVB, then their daily routines—such as sitting by a sunny window for morning light, working in glass-enclosed offices, or driving—are ineffective for health outcomes like Vitamin D production and circadian rhythm regulation. There is also specific concern that eyeglasses automatically block UV light, impacting critical bodily responses signaled through the optical system.
The Tip
To maximize the health benefits of light, ensure there is no glass barrier between your body and the natural light source, especially in the morning. If driving during sunrise, roll down the window to receive the critical light spectrum needed to anchor your circadian rhythm. Recognize that if your prescription eyeglasses block UV rays or blue light, they may also be interfering with important light signals to your mitochondria and pineal gland.
Creators Addressed
- Emphasized the importance of getting morning light exposure without glass between the eyes and the sun.
- Explained that the filtering properties of windows (including windshields) inhibit the entry of crucial wavelengths, thus undermining the light's ability to set the circadian clock.
- Mentioned that photochromic (darkening) glasses often fail to transition inside cars because the windshield blocks UV light—showing how auto glass prevents critical light exposure.
- Highlighted that people spend 93% of their time indoors, sealed off from vital wavelengths.
- Explained that Low-E glass filters out beneficial infrared light critical for mitochondrial health.
- Noted that the body needs UVB rays for Vitamin D, and these are mostly present when the sun is higher—and easily blocked by filters like glass.
Quick Summary (Do This Tonight)
Make a plan to step outside tomorrow morning, ensuring your eyes and skin receive light directly from the sky, bypassing all windows, screens, or regular eyeglasses.
How to Do It (Step-by-Step Breakdown)
- Avoid Glass: Never rely on light coming through a closed window (home or car) for your morning light exposure or Vitamin D synthesis.
- Open Barriers During Travel: If commuting during sunrise or sunset, and it is safe, roll down the car window to allow the unfiltered morning light to reach your eyes and skin.
- Check Eyewear: Be aware that standard prescription eyeglasses often contain UV and blue light filters that block beneficial signals your body needs to reset its circadian rhythm.
Common Mistakes & Fixes
Mistake: Assuming a sunny spot inside by a window is sufficient for biological light benefits.
Fix: Windows block critical spectrums like UVB and IR. You must be outdoors and exposed directly to the sky.
Mistake: Wearing photochromic or UV-blocking glasses during morning light exposure.
Fix: Remove all glasses or sunglasses during your brief morning sun viewing session.
Mistake: Assuming near-infrared light penetrates clothing or windows effectively.
Fix: Ensure light hits bare skin as much as possible to maximize mitochondrial effects.
Quick Answers (FAQ)
Does car glass block the good light?
Yes, windshields and car windows block the beneficial wavelengths, especially those needed for circadian alignment and Vitamin D synthesis.
Can older windows let in the benefits that newer Low-E windows block?
Older windows might allow more light through than modern Low-E glass, which is designed to filter infrared light. However, sitting by any window is generally ineffective for benefits like Vitamin D or melatonin production.
How do blue light blocking glasses affect the system?
Eyeglasses, especially those with built-in UV blockers, can prevent the full light spectrum from reaching the eyes, interfering with critical light signaling pathways.
Bottom Line
Glass separates us from the biological power of sunlight. To reclaim it, step outside—even for a few minutes each morning—to let the unfiltered spectrum reset your circadian rhythm, energize mitochondria, and support overall health.
How this was generated: This article compiles verified creator insights and audience commentary for structured comprehension.
Medical & Legal Disclaimer: This content is for educational purposes only. It is not medical or legal advice. Always consult a qualified professional before making decisions regarding health, medication, or substance use.
