"With a band gap of 4eV, glass can't absorb any photons with less energy than UVB light; namely, it is transparent to UVA, visible light, infared, etc; but the higher energy photons can and are highly likely to be absorbed."
So it seems hard to create glass that doesn't block UVB.
Found the answer on Quora: https://www.quora.com/Why-does-glass-block-UV
"With a band gap of 4eV, glass can't absorb any photons with less energy than UVB light; namely, it is transparent to UVA, visible light, infared, etc; but the higher energy photons can and are highly likely to be absorbed."
So it seems hard to create glass that doesn't block UVB.