Leaky Duct Repair in Santa Clara and the Peninsula: Get More From Every System You Run

Key Takeaways

1. Why Leaky Ducts Matter on the Peninsula

Bay breezes and marine air keep much of the Peninsula milder than the inland valleys, and Santa Clara sits in between. Because summers are gentler, some older homes here were built with a furnace only, and air conditioning or a heat pump was added later using the original ducts.

Those ducts were designed for heating. When you push cooling through them, every leak shows up as a room that never cools. Leaks also matter in winter: a back bedroom over a crawl space can stay chilly even with the heat running. ENERGY STAR estimates a typical home loses 20–30% of the air moving through its ducts, mild climate or not.

2. Signs Your Ducts Are Leaking

• One room stays cold in winter or warm on the few hot days
• Your new AC or heat pump doesn't feel as strong as promised
• Weak airflow at registers far from the equipment
• Dust or a musty smell when the system starts
• Ducts in a crawl space, attic or garage
• You're planning an equipment upgrade or a remodel

A duct leakage and airflow test measures both the leakage and the air reaching each room.

3. A Peninsula Example: Burlingame Job M-09

One documented job is a Burlingame home, listed in our data as M-09. Its starting leakage of 328 CFM25 was below our 400 CFM25 average.

That's 232 more cubic feet of air per minute reaching the rooms from the same equipment. By our runtime math, a 48% gain works out to roughly a third less runtime in theory, though real savings vary. For the full data set, see the Aeroseal results study.

4. Eichlers and Other Special Cases

Palo Alto and nearby cities have many Eichler homes. Many were built with radiant heating in the floor slab and no ducts at all. If your Eichler still heats only with radiant floors or uses ductless units, Aeroseal doesn't apply.

Some Eichler owners have added a ducted system later. Those ducts can leak like any others, and the process is the same. The same goes for additions and ADUs with their own small systems. In our data, an ADU system (M-08) went from 320 to 34 CFM25 and gained 24% airflow. A free consultation will tell you whether your home is a fit.

5. How Aeroseal Fixes Leaks From the Inside

Most duct leaks are hidden inside walls, floors and ceilings. Aeroseal seals them from the inside. We block every register, isolate the furnace and coil, pressurize the system and blow in a fine sealant mist. The particles stay in the air until they reach a leak, then collect at its edges until it closes.

Aeroseal seals gaps up to about 5/8 inch, so larger holes get hand-repaired first. A computer shows the leakage falling in real time. Aeroseal describes the sealant as non-toxic and ultra-low VOC. See how it works.

6. Step-by-Step: What Happens on Your Job

Our Typical Aeroseal Duct Repair Process

1. Free consultation. At your home or by video, we confirm you have ducts worth sealing and discuss your goals.
2. Baseline test. A calibrated Retrotec fan measures leakage at 25 Pascals (CFM25, or cubic feet per minute at that pressure), and a flow hood reads every register.
3. Hand repair. We reconnect separated joints, replace crushed sections and close gaps over 5/8 inch.
4. Aeroseal sealing. We seal with live monitoring. Aeroseal recommends occupants are out during this stage.
5. Final test and report. You get before and after leakage and airflow in writing.

Most single systems take one day.

7. Crawl Space Ducts and Air Quality

Many raised-floor homes in Santa Clara, Palo Alto and San Mateo run ducts through a crawl space. Down there, ducts get crushed, separated and stripped of insulation, and leaky returns can pull damp, dusty crawl space air into your rooms without passing the filter.

We fix the duct side: reconnecting and sealing runs, manual repair from $450 and re-insulation from $750. We don't do foundation or structural crawl space repair. If ducts are too dirty to seal, we clean them first for $500–$800. The EPA doesn't recommend routine cleaning without visible mold, pests or heavy debris. Read about ducts in crawl spaces and air quality.

8. Energy Savings: Bay Area-Wide Data

Searching for energy-efficient HVAC in Santa Clara often leads to new equipment. Tight ducts come first, because even efficient equipment loses air through leaks. These figures are from MaxSeal's 38 sealed systems across the Bay Area, not Peninsula-specific results.

Weaker systems gained the most. Results vary by home. See how much energy leaky ducts waste.

9. Adding AC or Switching to a Heat Pump

If you're replacing a furnace with a heat pump, the ducts will carry cooler supply air than before. Heat lost through leaks makes it feel cool at the register, which people call cold blow. Adding cooling to ducts designed for heating can also leave far rooms short of air.

MaxSeal doesn't install or repair heat pumps or AC. We test and seal the ducts so the new equipment can deliver what it was sized for. California's Title 24 generally requires duct leakage testing when equipment is replaced, so confirm the target with your contractor or building department. A Manual J load calculation (from $495) can also help size new equipment. See heat pump cold blow and Title 24 duct testing.

10. Why Peninsula Homeowners Choose MaxSeal

• Ducts only. No equipment to sell, so our advice follows your test.
• Documented results. Before and after numbers, like M-09 in Burlingame.
• Honest fit check. We tell you if your home, such as a radiant-only Eichler, isn't a candidate.
• Licensed and authorized. CA License #1128398, authorized Aeroseal dealer. Aeroseal lists a 10-year residential warranty that dealers can pass on.
• Better overall performance. Tight ducts help any system run as designed. See system performance.