California Title 24 requires mechanical ventilation in all new homes and most major remodels. Modern tight construction doesn’t leak enough air to ventilate naturally, so code mandates an active fresh-air system delivering 7.5 CFM per occupant plus 3 CFM per 100 sqft of conditioned space. ERVs (energy recovery ventilators) and HRVs (heat recovery ventilators) are the two systems that meet this requirement while keeping energy use low. Installed cost runs $1,500-$4,500 depending on system type and existing ductwork.
ERV vs HRV is the most common question. Here’s how it actually applies to San Diego homes.
ERV vs HRV in one paragraph
Both ERVs and HRVs use a heat exchanger to transfer heat between the outgoing stale air and the incoming fresh air, recovering 60-90% of the energy that would otherwise be lost. The difference: an ERV also transfers moisture between the two air streams; an HRV transfers only heat. ERVs are better in humid coastal climates and in dry climates with humidity-control needs. HRVs are better in cold climates where you want to dump moisture outdoors.
For San Diego: ERVs are the default choice for coastal and most inland homes. HRVs only make sense in specific inland scenarios.
What Title 24 actually requires
California’s energy code mandates mechanical ventilation in residential construction certified after 2008 (more restrictive after each three-year code cycle). The current rule (ASHRAE 62.2-2019, adopted by Title 24):
Whole-house ventilation rate: 7.5 CFM per occupant + 3 CFM per 100 sqft of conditioned floor area.
For a typical 2,000 sqft, 4-occupant San Diego home: (4 × 7.5) + (2,000 × 0.03) = 30 + 60 = 90 CFM continuous fresh air.
Acceptable systems:
- Continuous exhaust fan with passive intake (cheapest, $200-$600, but wastes conditioned air)
- Continuous supply fan (rarely used)
- Balanced ventilation with ERV or HRV (best, $1,500-$4,500)
- Central-fan-integrated supply ventilation (CFIS, $600-$1,500)
The exhaust-only approach meets code but throws away heated or cooled air. ERV/HRV captures most of that energy back. CFIS is a middle ground that uses the existing HVAC blower to pull in outdoor air through a controlled damper.
When required: every new construction project. Any addition over 1,000 sqft. Any “major renovation” that touches more than 50% of the conditioned envelope. Many remodels that replace HVAC equipment also trigger ventilation compliance.
Why San Diego usually picks ERV over HRV
The choice depends on climate. The ERV/HRV decision matrix:
| Climate type | Best choice | Reason |
|---|---|---|
| Hot humid (Houston, Miami) | ERV | Block humidity from entering |
| Cold humid (Minneapolis) | HRV | Dump indoor moisture outside |
| Hot dry (Phoenix) | ERV | Retain indoor humidity in summer |
| Mild humid (San Diego coastal) | ERV | Manage marine layer humidity |
| Mild dry (San Diego inland) | ERV | Retain indoor humidity in winter |
San Diego coastal humidity averages 65-75% with regular fog and marine layer days. Inland communities run dry in summer (20-40% RH) and modestly humid in winter (45-65%). An ERV moderates both extremes; an HRV doesn’t help with either.
The single exception: homes with persistent indoor moisture problems (basement-style construction, bathroom-heavy occupancy, indoor pool) sometimes benefit from an HRV’s tendency to dump moisture. Rare in San Diego residential.
Cost ranges in 2026
For typical San Diego single-family home installation:
| System type | Equipment | Installed cost |
|---|---|---|
| Exhaust-only (Panasonic WhisperGreen + intake) | $250-$500 | $600-$1,400 |
| CFIS (smart damper + outdoor sensor) | $400-$900 | $900-$1,800 |
| HRV (Renewaire, Broan, Zehnder) | $850-$1,800 | $1,800-$3,500 |
| ERV (Panasonic Intelli-Balance, Broan AI Series, Zehnder ComfoAir) | $1,000-$2,500 | $2,000-$4,500 |
| Premium ERV with HEPA filtration (Zehnder, IQAir Perfect 16) | $2,500-$5,000 | $4,500-$8,500 |
Installation complexity drives the upper end of each range. New construction during framing is cheapest. Retrofitting into a finished home with no existing ductwork pathways can push costs 40-60% higher than the new-construction equivalent.
When ERV retrofit pays off in San Diego
Title 24 only requires ventilation in new construction and major remodels. Older homes (pre-2008 construction) often have enough natural infiltration to ventilate adequately without mechanical help. That said, three retrofit scenarios make sense:
1. Wildfire smoke filtration. A balanced ERV with high-MERV or HEPA filtration provides clean outdoor air on smoke days. Most homes during fire events face an impossible choice: open windows for fresh air but get smoke, or close everything but suffocate. An ERV with proper filtration solves it. Retrofit cost: $3,000-$6,500. Worth it for asthma sufferers, families with young children, or homes in canyon-adjacent fire-risk zones.
2. Tight new home with comfort issues. Homes built 2015 or later with foam insulation and good air sealing often feel stuffy and have humidity or odor complaints. An ERV solves both. Symptom check: windows fog from inside in winter, persistent cooking smells, occupant complaints of stuffiness. Retrofit cost: $2,500-$5,000.
3. Bathroom-heavy or kitchen-heavy occupancy. Homes with multiple bathrooms running long showers, or heavy daily cooking, produce more indoor moisture than coastal air infiltration can handle. An ERV moderates without requiring open windows. Less common driver but real.
ERV sizing and CFM math
The Title 24 calculation gives total CFM. Sizing the ERV is straightforward:
| Home size | Occupants | Required CFM | Recommended ERV size |
|---|---|---|---|
| 1,200 sqft | 2 | 51 | 60-90 CFM |
| 1,800 sqft | 3 | 77 | 90-120 CFM |
| 2,400 sqft | 4 | 102 | 110-150 CFM |
| 3,200 sqft | 5 | 134 | 140-200 CFM |
| 4,000 sqft | 6 | 165 | 175-250 CFM |
Oversize 15-25% above minimum so the unit doesn’t run at maximum continuously. Continuous operation at 60-70% of rated capacity uses less energy and lasts longer than burst operation at 100%.
Integration with HVAC equipment
Three integration patterns are common in San Diego:
Standalone ERV (separate ducts, dedicated fresh-air vents and return points). Best performance, most expensive retrofit. The ERV operates independently of the heating/cooling system.
Tied-in ERV (ERV ducts connect to the return side of the air handler). Less expensive, uses existing distribution. The HVAC blower runs more often to circulate ventilation air, raising electric use slightly.
Smart-coupled ERV (ERV with integrated control linked to thermostat). Newer Broan AI Series and Panasonic Intelli-Balance units optimize runtime based on indoor RH, CO2, and outdoor conditions. Most efficient operation, slight cost premium.
For most San Diego retrofits, the tied-in approach is the right balance of cost and performance.
What besides ERV/HRV matters
Mechanical ventilation alone doesn’t solve every indoor air issue. Three things matter as much:
Filtration. MERV 13+ on the supply side blocks particles. See our HVAC filter MERV guide for what your system can actually handle.
Source control. Combustion appliances (gas range, gas furnace, gas water heater), off-gassing materials, and cleaning chemicals add load. A heat pump replacement removing combustion equipment reduces ventilation requirement effectiveness.
Humidity targets. Indoor RH should stay 30-50%. Below 30% causes dry-air symptoms; above 50% promotes mold and dust mites. An ERV moderates but doesn’t actively control humidity. That’s a whole-house dehumidifier or AC sizing question.
Decision framework
Building new in SD County: balanced ERV is the right answer. Spec it during design phase to integrate cleanly with HVAC.
Doing a major remodel that triggers Title 24: balanced ERV or CFIS depending on budget. CFIS is cheaper but uses more HVAC blower energy long-term.
Retrofitting an older home with no compliance pressure: justify the retrofit on wildfire smoke, indoor comfort, or occupancy load grounds. Not just because code says new houses need it.
Old leaky home with no comfort complaints: skip the ventilation upgrade. The infiltration is already ventilating the house. Spend the money on insulation and air sealing first, then revisit.
What to ask a contractor about ERV install
- “What’s my Title 24 required CFM for this house?”
- “Are you sizing the ERV to the calculated load plus 15-25% headroom?”
- “Will you tie into the existing HVAC return or run dedicated ventilation ducts?”
- “What filtration grade does this unit support, and what’s the filter replacement cost?”
- “Will the unit’s controls integrate with my thermostat or smart home system?”
- “What’s the manufacturer’s warranty on the heat exchange core?”
For more on indoor air quality at the home level, see what is indoor air quality in San Diego. For new-construction HVAC planning, see HVAC new construction San Diego Title 24.
FAQs
Is ERV required in California?
Mechanical ventilation is required by Title 24 in new construction and major remodels. ERV is one of four approved compliance paths. The others are HRV, exhaust-only with passive intake, and central-fan-integrated supply (CFIS).
What’s the difference between ERV and HRV?
Both recover heat between outgoing stale air and incoming fresh air. An ERV also transfers moisture between the streams; an HRV transfers only heat. ERV is better for San Diego’s mixed humidity climate.
How much does an ERV cost installed in San Diego?
$2,000-$4,500 for a typical retrofit on a 1,800-2,400 sqft home. New construction integrated during framing is cheaper. Premium HEPA-filtered models run higher.
Can an ERV help with wildfire smoke?
Yes, with proper filtration. A balanced ERV with MERV 13 or HEPA filtration on the supply side delivers filtered fresh air while keeping windows closed. One of the strongest arguments for ERV retrofit in fire-zone-adjacent SD homes.
Does my existing HVAC need to change to add an ERV?
Usually no, but the install method affects cost. Tying the ERV into the existing return ductwork is the most common retrofit approach. Standalone ERV systems (separate ducts) cost more but operate independently of the HVAC blower.
What’s the maintenance on an ERV?
Filter changes every 3-6 months, heat exchange core cleaning annually. Total annual maintenance cost runs $40-$120 in materials. Some premium units have washable cores; others have replaceable cores rated for 10-15 years.
When to call us
If you’re trying to figure out whether ERV makes sense for your San Diego home, what size you need, or how to integrate ventilation with an HVAC replacement, we’ll run through it honestly. Call (442) 777-6440 for a free in-home assessment.