Why it matters to you
A system that can't pull enough air in through its returns can't push enough out through its supplies, and over Houston's long cooling season restricted return air contributes to frozen coils, weak airflow, and rooms that never feel dry. Closing supply registers in unused rooms usually doesn't save energy in a ducted system; it raises duct pressure instead.
Practical guidance
Keep returns clear of furniture, rugs, and drapes, vacuum the grilles when you change the filter, and leave most supply registers open. If some rooms stay hot or a return whistles, ask a licensed technician to measure airflow and static pressure rather than adding or closing vents yourself.