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A large fraction of UV radiation is blocked even by single pane glass.

If the 'health' benefit or bio signal for this effect, requires UV radiation then there is very little that can substitute being outside for 1 or 2 hours a day depending on the season.



You don't need 100% UVI 11 damage 1-2hr a day. That large fraction removed is functioning well for him and preventing him from sunburn.


If we are talking about humans and the hormones associated with the 24-hour sleep/wake cycle, they are largely influenced by blue light which is in the visible spectrum. It's part of why screens without orange-shifting software will tend to keep you wide awake at night.

Interestingly, red wave (IR) light appears to influence cortisol levels but not melatonin. [1] IR also makes it through windows as any cat can attest.

Getting outside for an hour or two as often as possible, regardless of the season, is probably a good idea, but it doesn't appear to be strictly necessary for modulating circadian rhythms.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2905913/




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