MEP Plans in Altadena, CA
Permit-ready mechanical, electrical and plumbing plans for ADUs, garage conversions, additions and single-family homes in Altadena (unincorporated Los Angeles County), prepared for plan check at Los Angeles County Public Works – Building and Safety, with Title 24 available in the same order.
Altadena project facts we design around
| County | Los Angeles County (unincorporated) |
|---|---|
| Title 24 climate zone | Climate Zone 9, confirmed by ZIP for every project |
| Electric utility (most addresses) | Southern California Edison (SCE) |
| Permits issued by | Los Angeles County Public Works – Building and Safety |
| ADU permits issued, 2021–2025 | 517 |
| ADU approval timeline | Approve or deny within 60 days of a complete application (state law) |
ADU building activity in Altadena
Los Angeles County issued 517 ADU building permits from 2021 through 2025 for addresses in Altadena, based on the county's reports to the state. Permits went from 53 in 2021 to 271 in 2025.
| 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|
| 53 | 48 | 82 | 63 | 271 |
Source: California Department of Housing and Community Development, Annual Progress Report data (ADU building permits by year).
Title 24 in Climate Zone 9
- Windows: U-factor 0.30 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.
- Solar PV sized by the CEC formula kW = (floor area x 0.613) / 1000 + 1.36; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 718 sq ft or smaller.
Climate Zone 9 requirements in full →
HVAC design for Altadena
The California Energy Commission's design-day data for Altadena gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 92°F and a winter design temperature of 32°F.
| Summer design (1%) | 92°F dry bulb / 67°F wet bulb |
|---|---|
| Winter design (median of extremes) | 32°F |
| Daily temperature range | 31°F |
| Elevation | 1,200 ft |
| Heating degree days | 1,920 |
Both seasons matter here. The heat pump is usually sized for the 92°F cooling condition and then checked to confirm it still covers the heating load at 32°F.
Electrical service from Southern California Edison (SCE)
If the load calculation shows you need a service upgrade, a second meter or a relocated service, Southern California Edison (SCE) handles that through its Building, Renovation, and Project Planning Portal, separately from the building permit.
ADU electrical service with Southern California Edison (SCE) →
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.
Nearby places compared
| Place | Climate zone | Electric utility | ADU permits 2021–25 |
|---|---|---|---|
| Los Angeles | CZ 9, 8, 6, 16 | Los Angeles Department of Water and Power (LADWP) | 52,059 |
| Long Beach | CZ 6, 8 | Southern California Edison (SCE) | 3,015 |
| Glendale | CZ 9 | Glendale Water and Power | 2,945 |
| Burbank | CZ 9 | Burbank Water and Power | 1,376 |
| Torrance | CZ 6, 8 | Southern California Edison (SCE) | 1,051 |
| Downey | CZ 8 | Southern California Edison (SCE) | 1,020 |
Los Angeles County → · All California cities and communities →
Guides for Altadena projects
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Start My OrderGeneral guidance, not legal advice. Climate zone and utility are shown for most addresses in Altadena; requirements vary by project. Confirm with Los Angeles County Public Works – Building and Safety.