The third floor of the house had a serious heating and cooling problem. Multiple HVAC contractors looked at it. None had a solution that worked within a reasonable budget. So I designed and tested my own: 12-inch HVAC ducts hung from the ceiling, fed through two 12-inch AC Infinity inline fans, engineered for minimum noise and comfortable temperature without a full system redesign. The prototype validated the approach — pull the hottest air from the top of the three-story space, move it mechanically, and redistribute it. It worked well enough to prove the concept, which was the point. In 2023, the system was replaced with a proper HVAC installation, but only because the prototype had already answered the questions no contractor could: what airflow rate was needed, where the thermal boundaries actually were, and what “comfortable” meant in that space.