Most San Diego homes can lose a large share of conditioned air through duct leaks, especially with original ductwork from 1970-1995. ENERGY STAR says that in a typical house, about 20% to 30% of the air that moves through the duct system is lost because of leaks, holes, and poorly connected ducts. That is a national typical-house statement, not a measured CFM for your attic. Climate Pros SD does not publish a sealing or replacement dollar menu. The matched company quotes after a leakage test.
The fast answer
| Service | What the bid should name |
|---|---|
| Duct leakage test (blower door / duct blaster) | Test method, CFM25 result, pass/fail against the stated threshold |
| Light duct sealing | Accessible attic, named joints |
| Moderate duct sealing | Attic plus crawl space, several leaks |
| Major duct sealing | Tight access, many leaks |
| Full duct replacement | When sealing cannot restore airflow. Separate construction job, not a Climate Pros SD band. |
| Energy savings | Your kWh and SDG&E TOU plan. Not a published annual dollar range. |
For homes with significant leakage, sealing is often one of the highest-ROI HVAC jobs because it restores capacity you already paid for. Payback depends on how leaky the ducts actually are.
How duct leaks happen
Three primary failure modes in San Diego homes:
1. Seam separation over time. Sheet metal ducts have crimped seams that can loosen as the system heats and cools. Original ductwork installations rarely sealed seams beyond basic mechanical connection; sealant degrades or was never applied.
2. Flex duct deterioration. Flexible ducts (the silver foil-wrapped tubes) used in many newer installations can develop tears, holes from pest activity, or compression from being run over by HVAC techs or stored attic items.
3. Air handler cabinet leaks. The cabinet itself (where the indoor coil and blower live) often has poor sealing at seams, electrical wire passages, and the panel that opens for service. This single source can account for 15-25% of total system air loss.
In San Diego specifically, attic-mounted systems (common in older construction) see worse leakage rates than basement or closet-mounted systems because attic temperatures of 130-150F accelerate sealant degradation.
What duct leakage actually costs you
Real-world impact of 25% duct leakage:
| What | Impact |
|---|---|
| Cooling capacity loss | Matches the leakage fraction if supply ducts dump into the attic |
| SDG&E summer bill | Higher kWh than a tight system at the same setpoint |
| Uneven cooling between rooms | Significant (some rooms hot, some cold) |
| AC runtime hours | Higher |
| System wear | Extra runtime |
| Indoor air quality | Worse (leaks pull attic dust into the system) |
For an inland San Diego home, leakage shows up as extra summer kWh, not as a Climate Pros dollar table. Look at your SDG&E TOU bill and the test result. Over a 15-year system life, wasted runtime also wears the equipment.
How testing works
Two methods used in San Diego:
1. Duct Blaster test. A calibrated fan attached to the duct system pressurizes the entire duct network. Pressure decay over a set time period measures total leakage. Result: a specific leakage rate (in cubic feet per minute at 25 Pascals, or CFM25). Industry benchmark: under 6% of system airflow is acceptable; over 15% needs intervention.
2. Blower door + IR camera. A blower door pressurizes the whole house; an infrared camera reveals leaks at duct joints as temperature differentials. More qualitative than the duct blaster but useful for finding specific leak locations.
Test cost is a line on the quote. Climate Pros SD does not publish a test fee. Some companies fold the test into a larger efficiency visit. Ask which it is before they arrive.
If you’ve never had your ducts tested, you don’t know what your leakage rate is. Most homeowners are surprised, older homes routinely test at 30-45% leakage, sometimes higher.
How sealing actually works
Three sealing methods, used in combination:
1. Mastic sealant applied to all seams, joints, and connections. Mastic is a flexible, paint-like sealant specifically designed for ductwork. Cures to a permanent seal that handles thermal cycling.
2. Foil-backed tape (not regular duct tape, that’s actually a bad name for the wrong product). UL 181 listed foil tape for specific joint types where mastic isn’t appropriate.
3. Aeroseal injection. A spray sealant is injected into pressurized ductwork; it seeks out and seals leaks from the inside. More labor and material than mastic on open joints. Useful when ducts run through inaccessible spaces (between floors, behind walls). Ask for that as its own line. Climate Pros SD does not publish an Aeroseal band.
For most San Diego homes, mastic + foil tape on accessible ductwork is the right approach. Aeroseal makes sense when ducts run through inaccessible spaces (between floors, behind walls).
What sealing costs and what it saves
Climate Pros SD does not publish a sealing menu or a 2-to-4-year payback table. Ask for:
| Home situation | What to compare on the bid |
|---|---|
| Newer home with minor leaks | Accessible joints, mastic and foil tape |
| Older home with moderate leaks | Attic plus crawl space |
| Major leakage (older system, attic ducts) | Tight access, many joints, maybe partial replacement |
Non-dollar benefits still matter: more even room-to-room temperatures, less runtime (which can extend equipment life), and better indoor air quality.
When duct sealing isn’t enough
Three situations push toward full duct replacement:
1. Major flex duct deterioration. Tears, holes, or compressed sections that can’t be patched effectively.
2. Severely undersized ducts for the system. If the AC system is properly sized but the ducts can’t move enough air, sealing doesn’t help. Need bigger ducts.
3. Asbestos-wrapped ducts in older homes. Some pre-1980 San Diego homes have asbestos duct wrap. Repair work requires abatement, often making full replacement more cost-effective.
Full duct replacement is a construction job, not a Climate Pros SD published band. For homes with chronically bad ductwork that’s been patched repeatedly, it’s often the right answer when the next big repair comes due. Ask for replacement versus another round of sealing as two written scopes.
SDG&E incentives
SDG&E offers rebates for duct sealing through energy efficiency programs when a contractor program is actually open. Confirm current availability at sdge.com/rebates. Climate Pros SD does not publish a rebate dollar range.
Heat pump installs often include duct sealing as part of the project scope. If you’re considering both, doing them simultaneously captures more rebate dollar value than separate jobs.
San Diego-specific patterns
Three patterns we see most:
1. Tract homes from 1980-2000 with attic ducts. Builder-grade installations with minimal sealing. Leakage rates of 25-40% are typical. Highest-ROI sealing candidates in our service area.
2. Coastal homes with crawl space ducts. Marine humidity accelerates seam degradation. Often need both sealing and partial replacement. Carlsbad, Oceanside, Encinitas see this pattern.
3. Inland older homes with proper sealing. Some inland tract construction did use proper mastic at install. Leakage rates of 5-12% are common. Lower-priority for sealing intervention.
FAQs
How do I know if my ducts are leaking?
Signs: rooms farther from the air handler are hotter/colder than rooms close by, your SDG&E bill is higher than similar-sized homes, the air handler closet or attic feels conditioned, or dust accumulates on supply registers more than expected. Definitive answer: a duct leakage test. Climate Pros SD does not publish a test fee.
How much does duct sealing cost in San Diego?
Ask the matched company after they see access. Newer homes with minor leaks land at the low-labor end. Older homes with attic and crawl-space leaks take more time. Climate Pros SD does not publish a $300 to $1,200 sealing menu.
Is duct sealing worth it?
For homes with significant leakage (20%+ on a real test, or the ENERGY STAR typical-house 20% to 30% as a starting suspicion), yes. Comfort and runtime usually improve. Do not treat a blog payback table as a quote.
Can I seal ducts myself?
Some accessible leaks at the air handler cabinet and exposed joints can be sealed with mastic by a careful DIYer. Most attic and crawl space work, and any work requiring testing/verification, is better done by a pro.
What’s the difference between duct cleaning and duct sealing?
Cleaning removes dust and debris from inside the ducts. Sealing closes leaks at seams and joints. Different services for different purposes. Sealing is more impactful for energy and comfort.
Will duct sealing improve my indoor air quality?
Yes, often significantly. Sealed ducts can’t pull attic dust, fiberglass insulation, or pest debris into your indoor air. For homes with allergies or respiratory issues, this is a meaningful benefit beyond the energy savings.
Are there rebates for duct sealing in San Diego?
Sometimes, when a program is funded. SDG&E has offered rebates for verified leakage reduction through certified contractor programs. Ask at sdge.com/rebates. Climate Pros SD does not publish a $200 to $500 rebate.
How long does duct sealing last?
Mastic and foil tape sealing should last the life of the duct system (20-40 years). Aeroseal sealing also has long durability. Touch-up may be needed after major system service that disturbs the seals.
Related service: AC repair.
Not sure this is your symptom? Our HVAC symptom finder matches what the system is actually doing to the likely cause.
When to call us
If you suspect duct leakage is hurting your comfort and energy bills, we’ll run a duct leakage test as part of a comprehensive efficiency assessment. Call (442) 777-6440. For broader cooling cost reduction tactics, see our lower your AC bill guide.