Double-glazed window

Double-glazed windows were introduced in my apartment room arranged by mine yesterday, intending not the noise filtering but thermal control especially avoiding some dew condensation inside of the window glass surfaces.
I woke up this morning in a different atmospheric air condition, apparently my room temperature was warmer than before and no dew was found on the window glass anywhere!
Effects were enough to overcome the expenses of 300,000 yen per six windows at all?