Duct Sealing in Mountain View: Even Comfort for Mid-Century Homes, Townhomes and ADUs

Key Takeaways

1. Why Leaky Ducts Matter in Mountain View Homes

Mountain View grew fast after World War II. Census counts show the population rising from about 6,600 in 1950 to nearly 31,000 in 1960, so many single-family homes here date from that building boom. Many have since been remodeled, and a lot of them now have air conditioning or a heat pump running through ducts that were laid out decades ago.

The climate is mild, but September is usually the warmest month, and the city's record high is 107°F. On those days, leaks show up first in the rooms at the end of the longest runs. ENERGY STAR estimates a typical home loses 20–30% of the air moving through its ducts to leaks, holes and poor connections.

2. Eichlers and Other Mid-Century Homes

Mountain View's Monta Loma neighborhood is known for mid-century modern homes by Joseph Eichler, John Calder Mackay and the Mardell Building Company. Many Eichlers were built on concrete slabs with radiant heat, where hot water runs through tubing in the floor and there is no ductwork at all. If your home heats only that way, or cools with ductless mini-splits, Aeroseal doesn't apply, and we'll tell you so.

Some owners have added a ducted furnace, AC or heat pump later, often routed through the attic, a soffit or the garage. Those ducts can leak like any others. Other mid-century homes in the city were built with forced-air heat from the start. A free consultation, often by video, settles whether your home is a fit before you spend anything.

3. Townhomes and Condos

Census counts have put detached single-family houses at under a third of Mountain View's housing, so many residents live in townhomes and condos. If your unit has its own furnace, air handler or heat pump with ducts, those ducts can be tested and sealed like any house.

• We test only your unit's system and read airflow at each of your registers.
• Short runs in a townhome can still leak at the equipment, the plenum and the boots.
• Ducts in a shared attic or between floors are hard to reach by hand, which is where Aeroseal helps.
• If anything appears to connect to a shared building system, we stop and tell you before going further.
• Check your HOA's rules on contractor access and scheduling.

For whole-building questions, see condo and HOA duct sealing.

4. Signs Your Ducts Are Leaking

• A bedroom or home office runs warmer than the rest of the house
• Some registers blow hard while others barely move air
• A new AC or heat pump feels weaker than expected
• Dust builds up quickly, even with a good filter
• Ducts run through an attic, crawl space or garage
• A remodel, addition or ADU extended the original ducts

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

5. How Aeroseal Seals Without Opening Walls

Most duct leaks hide inside walls, floors and ceilings. Aeroseal reaches them from the inside, so 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 flex duct 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. Homes with more than one system take longer, and we'll give you a schedule up front.

7. Remodels, Additions and ADUs

Mountain View homes change a lot over time. A kitchen remodel moves a register, an addition hangs a long branch off the original trunk, and a backyard ADU gets a small system of its own. The joints between new and old ducts are a common place for leaks to start.

In our Bay Area data, one 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 Mountain View 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 than before. 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 return ducts 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.