Duct Sealing in Palo Alto: Tight Ducts for Older Homes, Remodels and Ducted Eichlers

Key Takeaways

1. Why Leaky Ducts Matter in Palo Alto Homes

Palo Alto's climate is mild, with moderately wet winters and warm, dry summers. Hot spells still happen. The city recorded 108°F in September 2022. Many older homes here were built for heating only, and air conditioning or a heat pump was added later using the original ducts.

North of Oregon Expressway, many homes are Craftsman and colonial-style houses built mostly in the first four decades of the 1900s, and Professorville has homes dating to the 1890s. These homes often had their duct systems added, extended or rerouted through remodels. ENERGY STAR estimates a typical home loses 20–30% of the air moving through its ducts, and the far rooms feel it first.

2. Eichlers: Check for Ducts First

Joseph Eichler built almost 3,000 homes in Palo Alto. Many Eichlers were built on concrete slabs with radiant heat: hot water runs through tubing in the floor, and there is no ductwork. If your Eichler still heats only with radiant floors or cools with ductless mini-splits, Aeroseal doesn't apply, and we'll tell you so.

Some Eichler owners have added a ducted system later, often routed through the attic, roofline or garage. Those ducts can leak like any others and can be tested and sealed the same way. A free consultation, often by video, settles whether your home is a fit.

3. Signs Your Ducts Are Leaking

• A back bedroom stays cold in winter or warm on hot days
• A new AC or heat pump doesn't feel as strong as expected
• 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
• A remodel or addition extended the original ducts

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

4. Crawl Space Ducts

Many older raised-floor homes run ducts through the 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'll point out crawl space problems we see. See ducts in crawl spaces.

5. How Aeroseal Seals Without Opening Walls

Most duct leaks hide inside walls, floors and ceilings. Aeroseal reaches them from the inside, so plaster, trim and finished rooms stay intact. We block every register, isolate the furnace and coil, pressurize the ducts and blow in a fine sealant mist. The particles stay airborne until they reach a leak, then build up at its edges until it closes.

Aeroseal seals gaps up to about 5/8 inch, so larger ones get hand-repaired first. A computer tracks leakage falling in real time. Aeroseal describes the sealant as non-toxic and ultra-low VOC. Read 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 talk through the rooms that bother you.
2. Baseline test. A calibrated Retrotec fan measures leakage at 25 Pascals (CFM25 means cubic feet per minute of leakage 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 jobs are done in a few hours.

7. Home Offices, Additions and ADUs

The rooms that matter most during the day are often the ones added last: a home office over the garage, a rear addition or a backyard ADU. They sit at the ends of long runs or on small systems of their own. In our Bay Area data, an ADU system (M-08) went from 320 to 34 CFM25 and gained 24% airflow.

Homes with two systems get each one tested and reported separately, and multi-system discounts apply. See the two-system case study.

8. What Changes After Sealing: Bay Area Data

These are MaxSeal's Bay Area-wide averages from 38 sealed systems. They are not Palo Alto results.

In theory, a 38% airflow gain means about 28% less runtime for the same delivered air. Results vary by home. See how much energy leaky ducts waste.

9. Heat Pumps, Smoke Season and Your Equipment

If you're replacing a furnace with a heat pump, the ducts will carry cooler supply air. Heat lost through leaks makes it feel cool at the register, which people call cold blow. California's Title 24 generally requires duct leakage testing when equipment is replaced, so confirm the target with your contractor or building department. MaxSeal works on ducts only, so we have no equipment to sell.

During wildfire smoke season, sealed returns pull less unfiltered air from the attic or crawl space, so more of your indoor air passes through the filter. See Title 24 duct testing and air quality.

10. Nearby Areas We Serve

MaxSeal also serves the communities around Palo Alto, including Atherton, Menlo Park, Woodside and Portola Valley, Redwood City, Mountain View, Sunnyvale, Los Altos and Los Altos Hills.