Climate ZonesZone 3C

Climate Zone 3C: Warm - Marine

Mild, marine climate with cool summers and mild winters. Moderate heating needs, minimal cooling.

Load Characteristic
Balanced Loads
Moisture Regime
Marine
States Covered
1 State

ASHRAE Design Temperatures

Official design temperatures for Climate Zone 3C per ASHRAE Fundamentals 2021. These values are critical for accurate Manual J load calculations.

Winter Design Temp
41°F

99% design temperature for heating load calculations (coldest expected temperature)

Summer Design Temp
81°F

1% design temperature for cooling load calculations (hottest expected temperature)

Wet Bulb Temp
63°F

Summer wet-bulb for latent cooling load and dehumidification calculations

2021 IECC Insulation Requirements

Minimum insulation and window specifications for Climate Zone 3C per the International Energy Conservation Code (IECC) 2021.

Wall Insulation
R-20

Minimum wall R-value (continuous insulation or cavity + continuous)

Roof/Ceiling Insulation
R-30

Minimum attic/ceiling R-value for energy compliance

Floor Insulation
R-19

Minimum floor R-value (over unconditioned space)

Window U-Factor
0.32

Maximum window U-factor (lower is better insulation)

Window SHGC
0.40

Recommended Solar Heat Gain Coefficient

Air Infiltration
0.15

Typical ACH (air changes per hour) for load calculations

Moisture Regime: Marine

Moderate temperatures with high moisture from ocean influence

Key Considerations for Marine Climates:

  • Year-round moisture management
  • Corrosion-resistant equipment
  • Marine-grade installations

Recommended HVAC Equipment

Typical equipment specifications for Climate Zone 3C installations.

Heating Systems

Gas furnace
Heat pump
Typical AFUE
90-95%

Cooling Systems

AC (often optional)
Heat pump
Typical SEER
14 SEER

States in Climate Zone 3C

Climate Zone 3C covers 1 state across the United States. Click a state to see city-specific climate data and Manual J load calculations.

California

Frequently Asked Questions About Climate Zone 3C

Q1What states are in Climate Zone 3C?

Climate Zone 3C includes the state of California. This zone represents a balanced climate with marine moisture conditions.

Q2What are the design temperatures for Zone 3C?

The official ASHRAE design temperatures for Climate Zone 3C are:

  • Winter 99% Design Temp: 41°F
  • Summer 1% Design Temp: 81°F
  • Summer Wet Bulb: 63°F

Q3What equipment works best in Climate Zone 3C?

For Climate Zone 3C (Warm - Marine), recommended HVAC equipment includes:

Heating Systems:
  • • Gas furnace
  • • Heat pump

Typical AFUE: 90-95%

Cooling Systems:
  • • AC (often optional)
  • • Heat pump

Typical SEER: 14 SEER

Q4What R-value insulation is required in Zone 3C?

IECC 2021 requires the following minimum R-values for Climate Zone 3C:

Walls
R-20
Roof
R-30
Floor
R-19
Window U
0.32

Q5Is Zone 3C heating-dominated or cooling-dominated?

Climate Zone 3C is a balanced climate. This means heating and cooling loads are relatively balanced, requiring careful sizing of both heating and cooling equipment.

Q6What is the moisture regime for Zone 3C?

Zone 3C has a marine moisture regime. This means coastal climate with marine influences, moderate humidity, and potential for condensation issues that require proper vapor barriers.

Get Accurate Load Calculations for Zone 3C

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