Duct Leakage & Airflow Testing in the Bay Area: Know Exactly Where Your Air Is Going
If one room is always too warm, another never cools down, or your bills keep climbing, the problem is often in ducts you can't see. A duct leakage and airflow test measures how much conditioned air escapes your ducts and how much actually reaches each room, so you can fix the real cause instead of guessing. At MaxSeal, testing starts at $295 and takes about an hour per system, and you get the numbers in writing.
Key Takeaways
| Common Question | Short Answer |
|---|---|
| What does a duct leakage test measure? | How many cubic feet of air per minute (CFM) leak from your ducts when they're held at 25 Pascals of pressure, reported as CFM25. How to read the report |
| How much does a duct leakage test cost? | MaxSeal's duct leakage and air volume test starts at $295. Consultations are free. See our price list |
| How long does it take? | About 30–60 minutes per HVAC system, plus a few minutes per register for airflow readings. |
| What is a good result? | Under 50 CFM25 is well sealed for a single home system, and under 30 is excellent. Over 400 usually means several rooms are starved for air. |
| Is the test different from a duct inspection? | Yes. An inspection looks at ducts you can see. A test measures the whole system, including ducts inside walls and floors. |
| What happens if my ducts leak a lot? | We show you which rooms are losing out and what sealing would likely recover. In our data, sealing raised airflow at the vents by 47% on average. See the results |
| Do I need a test when I replace my HVAC system in California? | Usually yes. Title 24 generally requires duct leakage testing when equipment or ducts are changed. Title 24 explained |
1. Why a Duct Test Beats Guessing
Most comfort complaints get treated with equipment: a bigger AC, a new furnace, a booster fan. If the ducts leak, new equipment pushes more air into the same holes. ENERGY STAR estimates that a typical home loses 20–30% of the air moving through its ducts. A test tells you whether that's happening in your home, and how badly, before you spend money on a fix.
2. What We Measure
| Measurement | Tool | What it tells you |
|---|---|---|
| Total duct leakage (CFM25) | Calibrated Retrotec duct-testing fan | How much air escapes the whole system |
| Leakage as % of system air | Calculated from the two readings | The share of conditioned air you're paying for and losing |
| Airflow at every supply register (CFM) | Flow hood | Which rooms get enough air and which are starved |
| Visual check of reachable ducts | Flashlight and camera | Disconnected, crushed or torn sections that need hand repair |
3. Signs You Should Get Your Ducts Tested
- One or more rooms are always hotter or colder than the rest
- Weak airflow from some vents, strong from others
- High heating and cooling bills in both summer and winter
- A dusty house, even after cleaning
- Ducts run through an attic, crawl space or garage
- You're about to replace your furnace, AC or heat pump
4. Step-by-Step: What to Expect During Your Test
Our Typical Duct Testing Process
- Walk-through. We talk about which rooms bother you and look at the equipment, filter and accessible ducts.
- Airflow readings. We measure airflow at every supply register with a flow hood.
- Leakage test. We temporarily seal the registers, connect the calibrated fan and measure leakage at 25 Pa.
- Report. You get a written summary with your leakage, room-by-room airflow and our recommendation.
The whole visit usually takes about an hour per system. Nothing is cut open and nothing is left sealed when we leave.
5. What a Real Report Looks Like
In a two-system home we tested in October 2026, the downstairs system was losing 561 CFM25, about 56% of its conditioned air. The kitchen register delivered only 10 CFM while the playroom got 68. Upstairs was losing 371 CFM25 (49%), and the master bathroom registers delivered just 17–18 CFM. With numbers like these, the homeowner could see why the kitchen and master suite never felt right.
6. How to Read Your Numbers
| Total leakage (CFM25) | What it typically means |
|---|---|
| Under 30 | Excellent, near-airtight |
| 30–50 | Well sealed (MaxSeal's standard target) |
| 50–150 | Moderate leakage, some rooms affected |
| 150–400 | Leaky, with noticeable comfort and efficiency loss |
| 400+ | Severe. Many rooms are likely starved |
These bands are MaxSeal's working guide for single residential systems, not a code standard. For a full walk-through, see how to read a duct leakage test report.
7. Test vs. Inspection vs. Full Diagnostic
| Duct leakage & airflow test | Visual duct inspection | Manual J & full diagnostic | |
|---|---|---|---|
| Price at MaxSeal | From $295 | Included in the test | From $495 |
| Measures hidden ducts | Yes | No | Yes |
| Room-by-room airflow | Yes | No | Yes |
| Static pressure and load per room | No | No | Yes |
| Best for | Leaks, uneven rooms, high bills | Obvious damage | Persistent problems, sizing questions, before replacing equipment |
If the test points to sizing or design problems, the Manual J load calculation and full diagnostic goes further.
8. What Happens After the Test
If your ducts are tight, you've ruled out a common cause and can look elsewhere. If they leak, we'll explain your options: hand repair for large gaps (from $450), Aeroseal sealing ($3,000–$3,500 per system), or both. Across 38 Bay Area systems MaxSeal sealed, leakage dropped by 86% on average and every system gained airflow.
Conclusion
A duct leakage and airflow test is the cheapest way to find out why your home feels uneven or costs so much to heat and cool. It measures the whole system, including the ducts you can't see, and gives you numbers you can act on.
Whether you end up sealing, repairing or doing nothing at all, you'll know exactly where your air is going.
Get a Free Consultation or call (408) 400-3630.
Related: How to read a duct leakage test report · Aeroseal results study · Price list · What to expect on seal day