Dunno about the 50% RH being "ideal." IME, it's whatever's sufficient
to avoid respiratory problems, without notable condensation on windows
of cooler parts of house.
In the case I'm familiar with, those windows are low-e, with original
el-cheapo storms, and the humidistat is set to around 25% RH.
If moisture is condensing on glass, consider what's happening inside
wall cavities and above the ceiling too.