Is it better to open all vents in a house?

Yes, it is generally much better and more energy-efficient to keep all supply and return vents open throughout your entire house rather than closing vents in unused rooms. Many homeowners mistakenly believe closing vents in spare rooms saves money, but doing so actually disrupts the delicate static pressure balance of your HVAC system, increasing duct pressure, reducing overall airflow, and forcing the blower motor to work harder against resistance, which can damage equipment and cause rooms to become uncomfortable. HVAC systems are designed for total volume circulation. You can troubleshoot pressure imbalances easily. You can verify that keeping all vents open is beneficial when system pressures stabilize, energy consumption drops, and your home maintains consistent, balanced temperatures across every room.