Sun & Skin
Can you tan through a window? Glass vs UVA and UVB
What glass blocks — and what slips through
| Glass | UVB (tanning/burning) | UVA (aging) |
|---|---|---|
| Standard window / office glass | ~99% blocked | Large share passes |
| Car windshield (laminated) | Blocked | Mostly blocked |
| Car side windows (tempered) | Blocked | Often 40–80% passes |
| Airplane windows | Blocked | Partially passes — at altitude UV is far stronger |
UVB is what makes melanin production kick off quickly and what burns — and it is exactly the band ordinary glass stops. That is why a whole afternoon in a sunny window leaves you pale. UVA is the sneaky one: it will not tan you meaningfully or burn you, but it drives wrinkles, pigment spots and long-term damage.
The driver’s-arm effect
Dermatologists see it constantly: more sun damage and skin cancers on the window side of the body — the left arm and left side of the face in countries that drive on the right. Windshields are laminated and filter UVA well; side windows usually are not. If you drive for a living, that side of your body is getting a daily UVA dose the other side is not. UV-blocking window film or simply sunscreen on the driving arm closes the gap.
Sunrooms, offices and planes
The same logic scales: no glass room will tan you, but a desk pressed against a sunny window for years is a slow UVA drip — worth a daily SPF on the face if that is your seat. Planes are the extreme case: at cruising altitude UV is roughly twice the ground value and windows pass part of the UVA; studies have measured notably higher melanoma rates in pilots and cabin crew. A window seat on a long-haul day flight is a legitimate reason for sunscreen.
Want the real tan instead? Take it outside, on your terms: a moderate UV index of 3–5 with SPF, per our tanning guide — and if the sky is grey, read what clouds actually do to UV first. The live UV for your city tells you whether right now is the moment.
Frequently asked questions
Can you get vitamin D through a window?
No. Vitamin D synthesis needs UVB, and glass blocks nearly all of it. Sitting by a sunny window feels warm but produces essentially no vitamin D — you need direct outdoor light or dietary sources.
Can you burn through a car window?
A sunburn through glass is very unlikely because UVB is blocked. Long drives still deliver UVA through side windows, which damages skin without the warning sign of a burn.
Do UV-blocking window films work?
Good films block up to 99% of both UVA and UVB and are an effective fix for cars, sunrooms and offices — the one glass upgrade that actually closes the UVA gap.
Does a tan through tinted windows count as safe?
Tint reduces visible light and some UV, but standard tint is not a UV certificate. If you can feel the sun on your skin for hours behind glass, assume UVA is reaching you and act accordingly.