Office HVAC in San Diego runs $8,000 to $30,000 for a typical tenant improvement and $60,000 to $250,000 for a building-wide retrofit. The reason the spread is wide: most multi-tenant office buildings here use a packaged rooftop unit feeding variable air volume (VAV) boxes for each suite, and the cost depends entirely on whether the existing VAV infrastructure stays or has to be ripped out. Get the zoning wrong and one tenant freezes while the next door tenant sweats.
Here’s how it actually works in Sorrento Valley, UTC, Carmel Mountain Ranch, Mission Valley, and the smaller office parks scattered through Kearny Mesa and Rancho Bernardo.
How multi-tenant office HVAC is built in SD
Most San Diego office buildings under 100,000 sqft use one of two layouts:
Layout 1: Per-suite rooftop unit. Each tenant gets a dedicated 3-10 ton packaged RTU. Simple to bill, easy to control after-hours use, expensive to install (more units, more curbs, more roof penetrations). Common in single-story office parks in Carmel Mountain and Rancho Bernardo.
Layout 2: Central RTU + VAV boxes. One or two larger rooftop units serve the whole floor through a duct trunk, with a VAV box and thermostat per suite. Cheaper to install per square foot, harder to bill fairly, and only works if the original commissioning was done right. Common in mid-rise buildings in UTC and Sorrento Valley.
The Layout 2 buildings are where most of the retrofit pain lives. The VAV boxes were balanced once, ten years ago, by an air-balance contractor who’s long gone. Tenants have been complaining ever since. New build-outs cut into the ducts. Reheat coils corroded. The system technically works but no one is comfortable.
What a tenant improvement HVAC scope actually costs
Real numbers from recent SD tenant improvement bids:
| Scope | Square footage | Typical cost |
|---|---|---|
| Reuse existing VAV, add 1-2 new zones | 1,000-2,500 sqft | $8,000-$14,000 |
| New VAV boxes, full rebalance, new thermostats | 2,500-5,000 sqft | $14,000-$30,000 |
| Add dedicated RTU for a single suite (data room, conference space) | 1,500-3,000 sqft | $18,000-$35,000 |
| Full floor rebuild (new duct, new VAVs, controls) | 8,000-12,000 sqft | $80,000-$180,000 |
| Title 24 economizer + DCV upgrade | per RTU >4.5 tons | $4,500-$9,000 per unit |
The big swing factor: are you keeping the existing controls or going to a new building management system (BMS). A BMS migration on a 30,000 sqft building runs another $40,000 to $120,000 just for controls.
Title 24 requirements you can’t skip
California Title 24 Part 6 applies to almost every office HVAC project in SD that pulls a permit. The pieces that drive cost:
Economizer mandate. Any unit larger than 4.5 tons cooling needs an air-side economizer (free cooling from outside air when conditions allow). Most SD office buildings have these, but a lot of them are broken or stuck closed. A failed economizer is a Title 24 violation when a permit is pulled, and it triples the building’s cooling energy use. Repair: $800 to $2,500 per RTU.
Demand-controlled ventilation (DCV). Spaces with design occupancy of 25+ people need CO2 sensors that modulate outside air. Conference rooms, training rooms, open-plan offices. The retrofit is $1,200 to $3,500 per zone if the BMS supports it.
Fan power limits. New VAV systems can’t exceed the prescriptive fan power budget. Oversized fans or old constant-volume systems get flagged in plan check.
Lighting + HVAC interlock. Occupancy sensors that control lights also have to set back HVAC in unoccupied zones. This is where a lot of older buildings can’t pass without controls work.
If you’re a tenant doing an improvement, the landlord owns the base building Title 24 compliance, but your suite-level changes still need to meet it. Plan for the permit + inspection cycle to add 4-8 weeks to the project.
After-hours zoning and the billing problem
After-hours HVAC is where multi-tenant office buildings either work or fall apart. Most leases say “HVAC is provided 7am-7pm weekdays.” A tenant who needs Saturday hours has to either pay an after-hours fee (typical $35-$85 per hour per zone in SD) or have their suite re-piped onto a dedicated unit.
If you’re a small business signing a 3-5 year lease in an SD office building, ask three specific questions:
- What’s the after-hours HVAC fee per hour, per zone, and how is “zone” defined?
- Is my suite on a dedicated RTU or shared VAV trunk?
- If shared, what’s the rebalance history? When was the last air balance report?
Question 3 separates the buildings that work from the buildings that don’t. A building with a recent (under 3 years) air balance report from a licensed test-and-balance contractor is in a different league than one that hasn’t been balanced since the property changed hands.
Common areas: who pays for what
Lobbies, corridors, restrooms, and shared conference areas typically run on a separate RTU billed to the landlord through CAM (common area maintenance). When the common area unit fails, every tenant feels it but no one tenant has the authority to fix it. This is a frequent source of complaint calls.
If you’re an owner-operator with one or two tenants, the cleanest approach is to put common areas on their own dedicated unit and bill it as a fixed line item rather than blending it into a shared trunk. Cleaner accounting, fewer fights.
Sorrento Valley vs UTC vs Carmel Mountain: what changes
Sorrento Valley. Lots of 1980s and 1990s office buildings with original Trane or Carrier RTUs that are now 25-35 years old. Most need full replacement, not repair. Marine layer corrosion on rooftop coils is real here, even four miles inland.
UTC. Newer high-rises with central plant chilled water systems, fan coil units per floor. Different equipment, different cost model. A tenant improvement here is mostly about VAV boxes and air balance, because the central plant is the landlord’s problem.
Carmel Mountain Ranch / Rancho Bernardo. Suburban office parks, mostly single-story, mostly Layout 1 (per-suite RTUs). Easier to scope, easier to bill, but each unit is older and the rooftop access can be a fall-hazard nightmare without OSHA-compliant railings.
Mission Valley. Mix of mid-century office buildings (challenging, undersized chases, asbestos in ceiling tiles) and newer construction near the trolley line. Plan extra contingency for unknowns in older Mission Valley stock.
When repair makes sense vs full replacement
A 15-year-old commercial RTU isn’t automatically toast. The decision tree we use:
- Under 12 years old, good service history, single failed component: repair.
- 12-18 years old, multiple recent failures, R-22 refrigerant: replace. R-22 phase-out makes leaks expensive to fix.
- Over 18 years old, any major component failure: replace. New units are 30-50% more efficient and qualify for SDG&E rebates.
SDG&E offers $300 to $1,200 per ton in commercial HVAC rebates depending on the unit’s efficiency rating, with bigger incentives for high-efficiency variable-speed units. The rebate paperwork has to be filed before the install, not after. Most contractors handle this, but verify it’s in the proposal.
FAQ
How much does it cost to replace HVAC in a 5,000 sqft San Diego office? A single 12.5-ton rooftop unit replacement runs $22,000 to $40,000 installed in SD, including crane rental and curb adapter. If you also need new VAV boxes and a rebalance, add $10,000 to $25,000.
Do I need a permit for office HVAC work in San Diego? Yes, for almost everything beyond filter changes. Equipment replacement, ductwork changes, new thermostats wired to building controls, and any refrigerant work all require a mechanical permit from the City of San Diego or the applicable city (San Diego, Carlsbad, Chula Vista, etc.). Plan 2-6 weeks for permit + inspection.
Can my landlord force me to pay for HVAC repairs in my leased office? Depends on your lease. Triple net (NNN) leases typically pass HVAC repair and replacement to the tenant. Modified gross leases usually keep major system repairs with the landlord. Read your lease’s HVAC repair clause before signing, this is one of the most-litigated lease provisions.
How long does an office HVAC tenant improvement take? 4 to 10 weeks typical, end to end. Two weeks for design and permit, 1-3 weeks for equipment lead time (longer for higher-efficiency units), 1-2 weeks of install work, 1 week for balance and final inspection.
What’s the difference between VAV and constant volume? Constant volume systems blow the same airflow all the time and adjust temperature by heating or cooling that fixed flow. VAV systems modulate airflow per zone based on demand. VAV is more efficient and more comfortable but more expensive to install and maintain. Almost all new SD office construction is VAV.
Why is my office freezing in one room and hot in the next? Three usual suspects. First, the VAV boxes are out of balance and one zone is starving for air. Second, the thermostat is sensing a hot or cold spot that’s not representative of the room. Third, an interior zone (no exterior walls) needs reheat that’s not working. All three are fixable but require a service tech to diagnose, not a tenant to guess.
Where to start
If you’re a tenant signing a new SD office lease, get the HVAC history before you sign. If you’re an owner with a building that’s getting complaints, start with a current air balance report from a licensed test-and-balance contractor (not your regular HVAC service company). That report tells you whether the system is broken or just out of tune.
For broader commercial HVAC context, see our commercial HVAC small business guide. For restaurant-specific HVAC, see restaurant HVAC in San Diego.
Call (442) 777-6440 for a free estimate. The technician we dispatch will walk your suite or building, review the existing equipment and any recent balance reports, and give you a written scope before any work starts.