Office Building Duct Sealing in San Jose: Fix Hot and Cold Suites and Wasted Fan Energy

Key Takeaways

1. Where Office Ductwork Leaks

Most Bay Area office buildings deliver air through sheet metal and flexible ducts hidden above suspended ceilings, fed by rooftop units (RTUs) or central air handlers. Leaks build up at joints, takeoffs, VAV (variable air volume) box connections and old patches from past remodels. Every tenant improvement adds more connections and more chances for gaps.

When supply ducts leak into the ceiling plenum (the open space above the ceiling that often serves as the return path), conditioned air short-circuits back to the unit without reaching the room. Leaky returns in shafts or unconditioned areas can pull in dust and unconditioned air.

2. Tenant Hot and Cold Complaints

Comfort complaints are often the first sign of duct trouble. Watch for these patterns:

• The same suites call every summer or every winter
• Zones at the end of long duct runs never reach setpoint
• Thermostats get adjusted, overridden or covered
• Space heaters and desk fans appear under desks
• Diffusers in one area barely move air while nearby ones blow hard

Rebalancing and controls work can help, but neither can deliver air that leaks out upstream. Measuring airflow at diffusers alongside total duct leakage shows whether the ducts are part of the problem. Our air balancing vs. duct sealing page explains why sealing usually comes first.

3. Fan Energy and Static Pressure

Static pressure is the resistance the fan pushes against, measured in inches of water column. When ducts leak, the system often compensates by running fans longer or faster to satisfy the zones that are short of air. That costs electricity every hour the building operates.

A 2023 U.S. General Services Administration (GSA) Green Proving Ground preliminary assessment of aerosol duct sealing cites manufacturer estimates of a 32% decrease in fan energy, a 2–4% cut in HVAC energy and a 2–7 year payback. The same report cites an ASHRAE estimate that about 75% of commercial buildings have duct leakage of 10–25%. Treat these as estimates. Your building's results depend on its systems, hours and starting leakage, which is why we test first.

4. Ventilation and Outdoor Air

Office HVAC systems bring in outside air to keep the indoor air fresh for tenants. If supply ducts leak before air reaches occupied spaces, some of that ventilation air never arrives where people work. Leaky return and exhaust ducts can also pull air from places it shouldn't come from, such as wall cavities or mechanical spaces.

Aeroseal describes its commercial work as improving comfort and indoor air quality while increasing energy efficiency, and says it has sealed ductwork in offices, hotels, hospitals, universities and government buildings. Aeroseal describes its sealant as non-toxic and ultra-low VOC. For more, see our air quality page.

5. TI Projects and Lease Turnover: The Best Times to Seal

Pairing sealing with planned work keeps tenant disruption low and lets your contractor coordinate around the same schedule.

6. Sealing in Sections Around Occupied Floors

Aeroseal's case studies show large systems sealed in sections. In one Aeroseal case study, a large hotel's existing ductwork was divided into six sections with foam blocks and sealed in three days ahead of a new VAV system, with total leakage reported falling from 12,414 to 613 CFM (cubic feet per minute at test pressure). The same sectioning approach suits office buildings, where you can seal one floor or one unit's ductwork at a time.

Our Typical Office Duct Sealing Process

1. Free consultation. We review drawings, tenant complaint history and upcoming TI or lease events with your team.
2. Baseline testing. We measure duct leakage and airflow at representative diffusers and note static pressures.
3. Plan the sequence. We pick systems or floors to seal on evenings, weekends or vacant periods.
4. Prep and hand repair. Diffusers are blocked, equipment is isolated and gaps larger than about 5/8 inch are repaired by hand.
5. Aeroseal sealing. Sealant is injected with live computer monitoring while the spaces served are unoccupied.
6. Final test and report. We retest and give you before and after results for each system.

7. Documenting Results for Ownership and Benchmarking

Asset managers want proof. Every system we seal gets a before and after leakage reading and airflow readings, delivered in a written report. That report supports capital planning, tenant communication and energy records.

If your building is covered by San Jose's Energy and Water Building Performance Ordinance, which the City says applies to privately owned commercial and multifamily buildings of 20,000 square feet or more, a measured efficiency improvement can be part of how you respond to the ordinance's Beyond Benchmarking requirements. Our explainer on building performance standards and duct sealing covers what the rules ask for. Rules change, so confirm current requirements with the City.