Diagnose weak airflow and room balance problems
Airflow problems are usually filters, returns, or duct issues. Pick the symptom that fits.
Vent barely blows
Filter, dampers, returns
One room hotter than the rest
Balance and insulation
One room colder than the rest
Damper or duct leak
Return air problem
Undersized returns
Filter choking airflow
MERV too restrictive
Dusty room
Filtration and seal gaps
Frequently asked questions
Why is one room hotter than the rest?
Usually undersized supply or return ducts, a closed damper, or poor insulation/leaky envelope. Check that vents and returns are unobstructed and the damper is open.
Can a high-MERV filter weaken airflow?
Yes. A MERV 13+ filter on a system designed for MERV 8 can starve airflow. Match the filter to the system's static pressure rating.
How do I know if my return air is undersized?
If the filter is sucked tight, the supply registers howl, or static pressure exceeds the equipment spec, the return is likely too small.