It makes sense to close HVAC registers when indoor temperature control becomes an issue.

Keep conditioned air out of rooms where you do not need it to keep the rest of the home comfortable, and save cash by not wasting unwanted heating and cooling.

But, it’s not that easy, as HVAC units and HVAC duct systems are designed to supply a particular volume of air to each room based on its square footage and one or more registers can affect that careful equilibrium. Unintended consequences can occur as your HVAC systems do not know whether all registers are open. As long as the control equipment is set, it produces the same amount of heated or cooled air and consumes the same amount of energy, and each room’s supply air volume is controlled by internal dampers inside the branch ducts. It ensures consistent uneven temperatures regardless of whether a room is near or far from the plan blower. When one or more supply registers are closed, airflow balance and uneven temperatures are disrupted. The rooms near the blower may acquire too much airflow, while rooms far away may not get enough. The supply vents may be closed to stop airflow, but the return registers remain open, and even without supply air the return plan draws air out of the room. This discrepancy depressurizes the room and/or space of the house. A depressurized room draws unfiltered cold or tepid outdoor air into the room through small structural cracks and gaps. This infiltrating air destabilizes room temperature and can degrade indoor air pollen levels. Closing supply vents increases static pressure inside the supply HVAC ducts, which in turn, stresses the plan blower, potentially leading to shorter repair life of that component.

Electric heat pump