In summer, the floor vent blows upward, while the ceiling vent lets out hot air. In winter, the ceiling vent blows downward, and the floor vent lets out cold air.-- galukalock, Jun 13 2003 Smart window fan http://www.halfbake...mart_20window_20fanSame idea for external air. [phoenix, Oct 21 2004] <voice source="everyone"><Hardy>I have nothing to say.</Hardy></voice>-- galukalock, Jul 09 2003 Where does the air come from? Go to?-- phoenix, Jul 09 2003 The HVAC system. This uses the Heating/Air system that most homes already have; the idea is merely to switch the direction of the airflow depending on the temperature of the air being moved, as hot air tends to rise and cold air tends to fall.-- galukalock, Jul 13 2003 random, halfbakery