Ductwork & Airflow 101
Your HVAC system can only perform as well as the air that moves through it. Proper airflow keeps rooms comfortable, protects your equipment, and ensures your system runs efficiently.
What Is Airflow?
Airflow in an HVAC system refers to how air travels through your ducts, vents, and filters. The system moves air from the return vents, through the furnace or air handler, and back into your living spaces through supply vents.
Think of it like your system’s bloodstream — when airflow is restricted, your HVAC system has to work harder to deliver the same comfort.
Understanding CFM (Cubic Feet per Minute)
CFM measures how much air your HVAC system moves in one minute. For example, a system designed for 1,200 CFM moves 1,200 cubic feet of air per minute through your ducts.
- Too little airflow → poor heating/cooling, frozen coils, and reduced efficiency.
- Too much airflow → noise, drafts, and uneven temperatures.
Static Pressure Explained
Static pressure is the resistance air faces as it moves through the system — like water pressure in a pipe. High static pressure means the blower motor has to work harder, reducing efficiency and comfort.
- Causes of high static pressure include dirty filters, undersized ducts, or blocked vents.
- Balanced systems have low static pressure and smooth airflow throughout the home.
Parts of the Duct System
- Supply ducts: Carry conditioned air from your HVAC system into rooms.
- Return ducts: Bring air back to be heated or cooled again.
- Registers & grilles: Cover the duct openings and direct airflow.
- Dampers: Control how much air flows to specific zones.
Common Airflow Problems
- Dirty or clogged air filters.
- Closed or blocked supply vents.
- Leaky or crushed ductwork.
- Improper duct sizing or layout.
- Undersized return air pathways.
How to Improve Airflow
- Replace filters every 60–90 days.
- Keep vents and returns open and unobstructed.
- Seal duct leaks with mastic or foil tape (not duct tape!).
- Have a pro measure static pressure and balance your system.
- Upgrade duct design if airflow problems persist.
Why Good Airflow Matters
Proper airflow reduces wear and tear, keeps temperatures even, and helps your HVAC system reach its rated efficiency. Even the best SEER2 or HSPF2 equipment can’t perform well without balanced airflow.
FAQ
How do I know if my HVAC has airflow problems?
Uneven room temperatures, weak airflow from vents, excessive noise, or longer run times are signs of restricted airflow.
Can I fix airflow issues myself?
Yes — start with simple fixes like replacing filters, cleaning vents, and checking for blocked ducts. Persistent issues may require a technician to measure static pressure and rebalance the system.
Related reads:
HVAC Components Explained · Manual J & Load Calculations
Shop the basics:
Filters · Ducting & Accessories · Thermostats