system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does defrosting a windscreen with both hot and cold air work?

Shouldn’t only one work and the other make it worse?
gpt
Blowing plain vent air will work, but it will take a long time.

Blowing air-conditioned vent air will work better, because one of the effects of air conditioning is that it removes moisture from the air.  So you're blowing cool, dry air.

Blowing warmed-up air-conditioned air works best.  The air conditioning dries it out, and the heat warms it up without adding any more moisture, so now you're blowing warm dry air.