I ducted a small stream of warmish air from the TEC output fan and radiator across the face of the window. Piece of soft rubber tubing jammed into the fins and trapped in a convenient slot in the tube extender worked extemely well.
You would build some really flash option with valves etc I'd guess knowing your build doctrine, I just use some rubber tube ...
But yes, hard to put a value on a DIY project of that nature.