Aeroseal Results: What 38 Bay Area Duct Sealing Jobs Actually Delivered (2026 Data)
You want to know whether Aeroseal actually works before you pay for it. Across 38 HVAC systems MaxSeal sealed with Aeroseal in the Bay Area, total system leakage fell from an average of 400 CFM to 54 CFM, an 86% reduction. Measured airflow at the supply registers rose by an average of 47% (median 38%), or about 225 more cubic feet of air per minute per system. If your system starts with more leakage, expect bigger gains: systems starting at 450–650 CFM averaged +64% airflow.
Key Takeaways
| Common Question | Short Answer |
|---|---|
| Does Aeroseal actually work? | In MaxSeal’s data from 38 systems, Aeroseal cut duct leakage by 86% on average and raised airflow at the registers by 47%. Every system improved, with gains from +10% to +182%. See our results |
| How much more airflow will I get after duct sealing? | It depends mostly on your starting leakage. Systems that started with 250–450 CFM of leakage gained a median of 33%, and systems that started with 450–650 CFM gained a median of 47%. How to read a duct leakage test |
| What is a good duct leakage number after sealing? | In this data the median ending leakage was 50 CFM25, and about 1 in 4 systems reached 30 CFM25 or less. MaxSeal’s usual target is under 50 CFM25. Duct leakage test |
| Which systems gain the most from sealing? | Systems that delivered less than 400 CFM to their rooms before sealing gained a median +38%, compared with +22% for systems that already delivered 700 CFM or more. Fix hot and cold rooms |
| Did every system improve? | Yes. The smallest airflow gain was +10% and the largest was +182%. Aeroseal case studies |
| Is this data independently verified? | No. It is MaxSeal’s own field data from calibrated test equipment, and each job’s before and after readings are recorded on site. |
| Should I test my ducts before replacing my furnace or AC? | Yes. A duct leakage test and a register-by-register airflow reading cost far less than new equipment, and a bigger unit pushing air into leaky ducts just leaks more air. Fix ducts before replacing HVAC |
1. Key findings
- 86% average leakage reduction. On the 35 systems with a post-seal leakage reading, leakage dropped from 400 CFM to 54 CFM on average.
- +47% average airflow at the registers (median +38%) across all 38 systems.
- Every system improved. The smallest gain was +10%. The largest was +182%.
- More leakage meant bigger gains. Systems that started at 450–650 CFM of leakage gained +64% on average. Systems that started at 250–450 CFM gained +36%.
- Half the systems got under 50 CFM of leakage. 18 of the 35 measured systems finished at or below 50 CFM, and 8 finished at or below 30 CFM.
- Starved systems gained the most. Systems that delivered less than 400 CFM to their rooms before sealing gained a median +38%, compared with +22% for systems that already delivered 700 CFM or more.
2. Results at a glance
| Metric | 250–450 CFM starting leakage | 450–650 CFM starting leakage | All systems |
|---|---|---|---|
| Systems sealed | 23 | 15 | 38 |
| Average starting leakage (CFM25) | 341 | 513* | 400* |
| Average ending leakage (CFM25) | 49 | 62* | 54* |
| Average leakage reduction | 85% | 88%* | 86%* |
| Average airflow gain at registers | +36% | +64% | +47% |
| Median airflow gain at registers | +33% | +47% | +38% |
| Average extra airflow delivered | +182 CFM | +291 CFM | +225 CFM |
| Smallest / largest gain | +10% / +79% | +20% / +182% | +10% / +182% |
*Based on the systems with a post-seal leakage reading (12 of 15 in the high-leakage group, 35 of 38 overall).
3. How airflow gains were distributed
| Airflow increase | 250–450 CFM group | 450–650 CFM group | All systems |
|---|---|---|---|
| Up to +20% | 4 | 1 | 5 |
| +21% to +35% | 8 | 3 | 11 |
| +36% to +50% | 6 | 4 | 10 |
| +51% to +80% | 5 | 3 | 8 |
| Over +80% | 0 | 4 | 4 |
Nearly 9 in 10 systems (33 of 38) gained more than 20% airflow at the registers, and 1 in 3 (12 of 38) gained more than 50%.
4. Job-level data
Customer names are replaced with job IDs. Leakage is total system leakage at 25 Pa. Airflow is the total flow-hood reading across all supply registers.
Systems starting at 450–650 CFM of leakage
| Job | Start leakage | End leakage | Airflow before | Airflow after | Gain |
|---|---|---|---|---|---|
| H-01 | 461 | 89 | 360 | 484 | +34% |
| H-02 | 463 | 39 | 435 | 601 | +38% |
| H-03 | 469 | 92 | 495 | 895 | +81% |
| H-04 | 485 | 53 | 238 | 670 | +182% |
| H-05 | 493 | 8 | 433 | 590 | +36% |
| H-06 | 499 | 35 | 703 | 963 | +37% |
| H-07 | 507 | 51 | 559 | 887 | +59% |
| H-08 | 529 | n/m | 359 | 581 | +62% |
| H-09 | 539 | 46 | 475 | 747 | +57% |
| H-10 | 546 | 56 | 259 | 635 | +145% |
| H-11 | 547 | n/m | 460 | 675 | +47% |
| H-12 | 554 | 102 | 667 | 869 | +30% |
| H-13 | 565 | 80 | 876 | 1,752 | +100% |
| H-14 | 579 | 97 | 1,073 | 1,289 | +20% |
| H-15 | 630 | n/m | 472 | 590 | +25% |
Systems starting at 250–450 CFM of leakage
| Job | Start leakage | End leakage | Airflow before | Airflow after | Gain |
|---|---|---|---|---|---|
| M-01 | 253 | 59 | 783 | 898 | +15% |
| M-02 | 283 | 44 | 205 | 242 | +18% |
| M-03 | 289 | 130 | 975 | 1,288 | +32% |
| M-04 | 292 | 30 | 307 | 437 | +42% |
| M-05 | 292 | 30 | 434 | 631 | +45% |
| M-06 | 308 | 42 | 528 | 720 | +36% |
| M-07 | 310 | 60 | 482 | 826 | +71% |
| M-08 | 320 | 34 | 331 | 411 | +24% |
| M-09 | 328 | 50 | 484 | 716 | +48% |
| M-10 | 328 | 94 | 401 | 562 | +40% |
| M-11 | 329 | 28 | 566 | 692 | +22% |
| M-12 | 333 | 88 | 640 | 733 | +15% |
| M-13 | 337 | 52 | 504 | 784 | +56% |
| M-14 | 338 | 43 | 530 | 743 | +40% |
| M-15 | 341 | 23 | 281 | 504 | +79% |
| M-16 | 347 | 34 | 763 | 921 | +21% |
| M-17 | 360 | 18 | 970 | 1,068 | +10% |
| M-18 | 372 | 52 | 981 | 1,194 | +22% |
| M-19 | 399 | 47 | 325 | 400 | +23% |
| M-20 | 409 | 26 | 277 | 368 | +33% |
| M-21 | 414 | 63 | 669 | 1,023 | +53% |
| M-22 | 421 | 65 | 779 | 985 | +26% |
| M-23 | 432 | 24 | 488 | 754 | +55% |
n/m = no post-seal leakage reading was taken on that job.
5. Methodology
- Who: Residential HVAC systems sealed by MaxSeal LLC with the Aeroseal process in the San Francisco Bay Area. Where one home had more than one system sealed, each system is listed separately.
- Leakage: Total system leakage measured in CFM at 25 Pascals (CFM25) with a calibrated Retrotec duct-testing fan, before and after sealing. This is whole-system leakage, not leakage to the outside only.
- Airflow: The total of flow-hood readings at every supply register, measured before and after sealing.
- Selection: Jobs with a starting leakage between 250 and 650 CFM25. Jobs outside that range are not included.
- Limits: This is a contractor’s own job data, not a controlled study. Results depend on duct layout, equipment and the condition of the ducts. Your results will vary.
6. What this means for homeowners
- If some rooms barely get air, leakage is a likely cause. The biggest gains in this data came from systems that were losing most of their air before it reached the rooms.
- Test before you replace equipment. A duct leakage test and a register-by-register airflow reading cost far less than a new furnace or AC. A bigger unit pushing air into leaky ducts just leaks more air.
- Ask for numbers, not adjectives. A good duct sealing contractor gives you before and after CFM25 and airflow readings, like the ones above. See how to read a duct leakage test report.
Conclusion
MaxSeal’s data from 38 Bay Area systems shows what Aeroseal typically delivers: leakage cut by 86% on average and airflow at the registers up 47%. Every system improved, and the leakiest systems gained the most.
This is a contractor’s own job data, so your results will vary. The way to know what your home could gain is to test it first and ask for the numbers in writing.
Get a Free Consultation or call (408) 400-3630.
Related: Leakage reduction by job · Our results · Aeroseal case studies · Recent projects · How Aeroseal works