MEP Plans in Catheys Valley, CA

Catheys Valley project facts we design around

County	Mariposa County (unincorporated)
Title 24 climate zone	Climate Zone 12, confirmed by ZIP for every project
Electric utility (most addresses)	Pacific Gas and Electric (PG&E)
Permits issued by	Mariposa County Building Department
ADU permits issued, 2021–2025	5
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Catheys Valley

Mariposa County issued 5 ADU building permits from 2021 through 2025 for addresses in Catheys Valley, based on the county's reports to the state. Permits went from 3 in 2023 to 2 in 2024.

2021	2022	2023	2024	2025
not reported	not reported	3	2	not reported

Source: California Department of Housing and Community Development, Annual Progress Report data (ADU building permits by year).

Title 24 in Climate Zone 12

• Windows: U-factor 0.27 or lower and solar heat gain coefficient (SHGC) 0.23 or lower, with total window area up to 20% of floor area (west-facing up to 5%).
• Whole-house fan required (at least 1.5 cfm per square foot of floor area); units of 500 sq ft or less are exempt.
• Cool roof required: steep-sloped roofs need aged solar reflectance 0.2 or higher and thermal emittance 0.75 or higher.
• Solar PV sized by the CEC formula kW = (floor area x 0.613) / 1000 + 1.4; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 653 sq ft or smaller.

Climate Zone 12 requirements in full →

HVAC design for Catheys Valley

The California Energy Commission's design-day data for Catheys Valley gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 98°F and a winter design temperature of 21°F.

Summer design (1%)	98°F dry bulb / 68°F wet bulb
Winter design (median of extremes)	21°F
Daily temperature range	38°F
Elevation	1,000 ft

Both seasons matter here. The heat pump is usually sized for the 98°F cooling condition and then checked to confirm it still covers the heating load at 21°F.

Electrical service from Pacific Gas and Electric (PG&E)

If the load calculation shows you need a service upgrade, a second meter or a relocated service, Pacific Gas and Electric (PG&E) handles that through its Your Projects portal, separately from the building permit.

ADU electrical service with Pacific Gas and Electric (PG&E) →

Plumbing and sewer

The plumbing plan shows the route, slope and cleanouts of the connection to the existing sewer lateral or septic system.

Pricing is flat statewide: ADU plans from $995, full ADU MEP package from $2,295, Title 24 add-on $240. See what's in a complete ADU MEP set.