MEP Plans in Napa County, CA
Permit-ready mechanical, electrical and plumbing plans for ADUs, garage conversions, additions and single-family homes anywhere in Napa County, in its cities and in unincorporated areas, with Title 24 available in the same order.
Napa County project facts we design around
| County seat | Napa |
|---|---|
| Population | 132,727 (Census 2024 estimate) |
| Incorporated cities | 5 |
| Unincorporated residents | About 20,505 (15% of the county) |
| Permits in unincorporated areas | Napa County Planning, Building & Environmental Services – Building Division |
| Title 24 climate zones | Climate Zone 2. Confirmed by ZIP for every project |
| ADU approval timeline | Approve or deny within 60 days of a complete application (state law) |
HVAC design across Napa County
Climate Zone 2: North Coast inland climate — warm dry summers, cool winters.
Summers are warm and dry while winters are cool and wet, so the heat pump has to cover both seasons well. Many projects here are rebuilds or additions on older lots, so confirming the existing service, panel and sewer before design avoids redesign later.
- Heat pump sized for both heating and cooling seasons
- Existing service and panel capacity confirmed before layout
- Ventilation and moisture control for wet winters
Unincorporated Napa County
Unincorporated communities are permitted by the county, not by a city. County plan check reviews MEP drawings against the same California Mechanical, Electrical and Plumbing Codes and the Title 24 Energy Code as any city, but the submittal checklist, forms and fees are the county's own, so we prepare the set to match. In rural areas, parcels outside a sewer district often rely on a private septic system; adding an ADU can require the county's environmental health division to confirm the system has capacity, and the plumbing plan then shows the connection to the septic tank instead of a sewer lateral.
What's in a Napa County MEP set
- Mechanical: HVAC layout, Manual J load calculation, equipment schedule, exhaust and whole-unit ventilation
- Electrical: power and lighting plan, panel schedule, NEC 220 load calculation, single-line diagram
- Plumbing: supply and DWV layout, fixture units, water heater, gas (if any), sewer or septic connection
- Title 24 (add-on): energy compliance for your address's climate zone, coordinated with the MEP design so the two documents agree
Pricing is flat statewide: ADU plans from $995, full ADU MEP package from $2,295, Title 24 add-on $240. Standard turnaround is 5 business days with two revisions and corrections included.
Napa County cities
| Place | Climate zone | Electric utility |
|---|---|---|
| American Canyon | CZ 2 | Pacific Gas and Electric (PG&E) |
| Calistoga | CZ 2 | Pacific Gas and Electric (PG&E) |
| Napa | CZ 2 | Pacific Gas and Electric (PG&E) |
| St. Helena | CZ 2 | Pacific Gas and Electric (PG&E) |
| Yountville | CZ 2 | Pacific Gas and Electric (PG&E) |
Shown for most addresses in each city. We also serve every unincorporated community in the county.
Napa County ADU MEP questions
Who issues building permits for an ADU in unincorporated Napa County?
In unincorporated areas, home to about 20,505 residents (15% of the county), ADU and residential permits go through Napa County Planning, Building & Environmental Services – Building Division. Inside the county's 5 incorporated cities, that city's own building department reviews the plans instead. We prepare the MEP set for whichever office has jurisdiction over your address.
What Title 24 climate zones are in Napa County?
All of Napa County is in California Climate Zone 2 on the Energy Commission's ZIP-code list. The climate zone drives the Title 24 energy calculation and the HVAC sizing.
Who provides electric service in Napa County?
It depends on the address. In the Napa County places listed on this page, most addresses are served by Pacific Gas and Electric (PG&E). We confirm the serving utility for every project, because service upgrades and new meters are requested from the utility, separately from the building permit.
How much do ADU MEP plans cost in Napa County?
Our pricing is flat across California: single-discipline ADU plans start at $995, a full MEP package for an ADU up to 600 SF is $2,295, and a Title 24 report can be added for $240. Residential (single-family) full MEP packages start at $3,495. Standard turnaround is 5 business days, and corrections are included.
How long does ADU approval take in Napa County?
California law requires local agencies, counties included, to approve or deny a complete ADU permit application within 60 days. Incomplete or inconsistent drawings are the most common reason the clock restarts, which is why MEP plans that match the architectural set, and a Title 24 report that matches the MEP design, matter.
Guides for Napa County projects
Ready for permit-ready MEP plans in Napa County?
Upload your architectural plans, get an instant flat price, and receive PDF plans in about 5 business days.
Start My OrderGeneral guidance, not legal advice. Population figures are Census Bureau 2024 estimates; climate zones are from the California Energy Commission's ZIP-code list, weighted by population. Requirements vary by project: confirm with Napa County Planning, Building & Environmental Services – Building Division or your city's building department.