Yes. The part of sunlight most associated with visible aging passes straight through ordinary window glass. Glass absorbs nearly all UVB, the wavelength that burns you, but it is far less effective against UVA, the longer wavelength linked to wrinkling, loss of firmness, and uneven pigment. The hours you spend driving or sitting beside a sunny window still count.
TL;DR: Window glass stops most UVB but lets a meaningful share of UVA through, and UVA is the wavelength tied to how old your skin looks rather than whether it burns. Laminated windshields block almost all of it; side windows are inconsistent and sometimes block less than half. If you commute by car or work near a window, a morning moisturizer with SPF earns its place in November as much as it does in July.
Does UV actually come through window glass?
Some of it does. Standard glass absorbs almost all UVB, which is why you don't get a sunburn through a closed car window. UVA behaves differently. It has a longer wavelength, penetrates deeper into the skin, and passes through glass far more readily. Dermatology divides the two roughly this way: UVB burns, UVA ages.
How much gets through depends on the glass. A 2016 study in JAMA Ophthalmology measured UVA transmission in 29 cars from 15 manufacturers and found that front windshields blocked 95 to 98 percent of UVA, while the driver's side windows blocked about 71 percent on average, with enormous variation between models. One car's side window blocked 95 percent; another blocked 44 percent. Windshields are laminated, with a UVA-absorbing plastic layer between two sheets of glass. Side and rear windows are usually tempered, and tempering does nothing for UVA.
Is the driver's-side face thing real?
There is at least one well-documented case of it. In 2012, The New England Journal of Medicine published a photograph of a 69-year-old man who had driven a delivery truck for 28 years. The left side of his face, the side facing the window, showed markedly deeper wrinkling, thickening, and sagging than the right. His doctors called it unilateral dermatoheliosis — one-sided sun damage.
That's one case after nearly three decades of unusually heavy exposure, not a prediction about your commute. But it shows the mechanism cleanly: UVA damage is cumulative and gradual, it never announces itself with a burn, and over a long enough stretch it surfaces as texture and laxity rather than redness.
Does any of this matter once it's cold out?
More than most guys assume. UVB drops sharply in winter at northern latitudes, which is why nobody burns in November — and why the daily SPF habit tends to quietly disappear around now. UVA declines far less across the seasons and passes through cloud cover readily. The American Academy of Dermatology notes that up to 80 percent of the sun's UV rays penetrate clouds, which is a reasonable argument against treating a gray morning as a day off.
Winter also changes the angle. The sun sits lower, so on a morning or evening commute it comes in through the side window at your face rather than down through the roof. The exposure you'd most want to block is the one most likely to reach you.
What routine actually accounts for this?
Two halves: protect daily, and address what has already accumulated. The protection half is the easier one, because it doesn't require adding a step. AM, Tiege Hanley's morning moisturizer with SPF 20, is the moisturizer you'd be using anyway, with sun protection built in. Worth being straight about the number: the AAD recommends broad-spectrum SPF 30 or higher for real time outdoors, so a dedicated sunscreen still belongs in your bag for a ski day or a long round of golf. For a commute-and-office day, SPF 20 you actually apply every morning does more than SPF 50 sitting in a drawer.
The second half is where cumulative exposure gets handled, and that's the thinking behind Level 3: The Anti-Aging Routine. It's the six-product version of the core system — WASH, SCRUB, AM, PM, EYES, and SUPER SERUM, which combines retinyl palmitate, sodium hyaluronate, and peptides to help soften the appearance of fine lines and support firmness. If your main concern is years of accumulated sun rather than breakouts or basic dryness, Level 3 is the level that matches the problem. We've written separately about what can and can't be undone after a summer of sun, and about why the cooler months are a sensible time to start a retinol product.
Common questions about sun through glass
Can you get sunburned through a car window?
Almost never through a closed window. Burning is driven by UVB, and glass absorbs nearly all of it. That's exactly why the exposure goes unnoticed — the feedback signal that normally tells you you've had too much sun is the thing glass filters out.
Does window tint help?
It can. Many aftermarket films are built to block most UVA, and some do it clear, without darkening the glass. If you drive for a living, ask an installer about a UV-blocking film.
Do you need SPF indoors if you're not near a window?
Not for UV. In an interior room with no daylight, no meaningful UV reaches your face. The practical problem is that most of us move between desks, windows, cars, and errands without recalculating, which is the argument for applying it in the morning and not thinking about it again.
Does a moisturizer with SPF count as sunscreen?
For incidental daily exposure, yes — it's a regulated sunscreen product and it's tested as one. For sustained time outdoors, it isn't a substitute for a dedicated broad-spectrum SPF 30 or higher applied generously and reapplied every two hours.
