I wonder if glass windows would block out the benefits?

Yes it does block [1]. Coincidentally I was discussing this with a co-worker last week.

[1]: http://www.sciencefocus.com/qa/can-you-absorb-vitamin-d-thro...

Ordinary window glass blocks 90% of UV-B which is needed to produce VitD.

I do remember reading years ago about a sanitarium in the late 1800's - early 1900 where the windows in the sun rooms were quartz glass.

Anecdotally, a lot of window products have built in films, coatings, or dopants that reduce UV exposure and possibly other portions of the spectrum.

I would /guess/ that pure (greenhouse?) glass, maybe not even visibly transparent, would be effective.

Both could be worth studying if someone hasn't already.

Glass itself blocks a lot of UV. Even not doped.

There exist optically transparent plastics that do not.