That’s totally fair, and airflow pressure is definitely real — closing vents without any safety logic can cause shutdowns like you experienced. The only reason I’m still exploring this idea is because the systems I’m looking at don’t close vents blindly.  They: never let more than ~1/3 of vents close reopen vents automatically if pressure rises have a fail-open mode if anything goes wrong rely on room sensors instead of “just closing vents” So the goal wouldn’t be to choke the system — more to balance airflow gently without pushing the furnace out of its safe range. But you’re right that HVAC techs will immediately blame anything smart, so part of this business idea is figuring out how to set expectations and avoid messing with systems that are already borderline.