MEP Plans in Imperial, CA

Imperial project facts we design around

County	Imperial County
Title 24 climate zone	Climate Zone 15, confirmed by ZIP for every project
Electric utility (most addresses)	Imperial Irrigation District (IID)
Permit review	The City of Imperial building department
ADU permits issued, 2021–2025	110 (#205 of 450 cities)
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Imperial

Imperial issued 110 ADU building permits from 2021 through 2025, the 205th most among the 450 California cities that reported ADU permits. Permits went from 3 in 2021 to 39 in 2025.

2021	2022	2023	2024	2025
3	15	30	23	39

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

Title 24 in Climate Zone 15

• Windows: U-factor 0.30 or lower and solar heat gain coefficient (SHGC) 0.20 or lower, with total window area up to 20% of floor area (west-facing up to 5%).
• Cool roof required: steep-sloped roofs need aged solar reflectance 0.2 or higher and thermal emittance 0.75 or higher; low-sloped roofs 0.63 / 0.75.
• Solar PV sized by the CEC formula kW = (floor area x 1.56) / 1000 + 1.47; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 212 sq ft or smaller.

Climate Zone 15 requirements in full →

HVAC design for Imperial

The California Energy Commission's design-day data for Imperial gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 107°F and a winter design temperature of 29°F.

Summer design (1%)	107°F dry bulb / 72°F wet bulb
Winter design (median of extremes)	29°F
Daily temperature range	31°F
Elevation	-64 ft
Heating degree days	976

Cooling governs equipment size here. At 107°F design conditions, west-facing glass, attic insulation and duct location move the load more than anything else, and the heat pump's electrical load has to be carried into the panel calculation.

Electrical service from Imperial Irrigation District (IID)

If the load calculation shows you need a service upgrade, a second meter or a relocated service, open that request with Imperial Irrigation District (IID) early; utility lead times are often longer than plan check.

Plumbing and sewer

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

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.