How to fix weak air flow from vents in house?

Fixing weak airflow coming out of your home's supply vents requires a systematic troubleshooting approach to identify and eliminate restrictions in your heating and cooling system. First, check and replace your indoor air filter, as a severely clogged filter is the most frequent cause of restricted airflow. Second, ensure all supply registers and return grilles throughout your home are fully open and unobstructed by furniture, carpets, or drapes. Third, inspect your accessible basement or crawlspace ductwork for disconnected joints, crushed flexible runs, or closed balancing dampers. Fourth, consider cleaning your indoor evaporator coil or upgrading your blower motor settings. You can troubleshoot airflow velocity using your hand or an anemometer. You can verify that your corrective actions were successful when powerful, steady air rushes out of every supply vent.