Climate ZonesZone 1A

Climate Zone 1A: Very Hot - Humid

Cooling-dominated climate with extreme heat and high humidity year-round. Minimal heating requirements.

Load Characteristic
Cooling-Dominated
Moisture Regime
Humid
States Covered
2 States

ASHRAE Design Temperatures

Official design temperatures for Climate Zone 1A per ASHRAE Fundamentals 2021. These values are critical for accurate Manual J load calculations.

Winter Design Temp
44°F

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

Summer Design Temp
94°F

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

Wet Bulb Temp
78°F

Summer wet-bulb for latent cooling load and dehumidification calculations

2021 IECC Insulation Requirements

Minimum insulation and window specifications for Climate Zone 1A per the International Energy Conservation Code (IECC) 2021.

Wall Insulation
R-13

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-13

Minimum floor R-value (over unconditioned space)

Window U-Factor
0.40

Maximum window U-factor (lower is better insulation)

Window SHGC
0.25

Maximum Solar Heat Gain Coefficient

Air Infiltration
0.25

Typical ACH (air changes per hour) for load calculations

Moisture Regime: Humid

High humidity climate requiring significant moisture control

Key Considerations for Humid Climates:

  • High dehumidification loads
  • Mold/mildew prevention critical
  • Proper vapor barriers essential

Recommended HVAC Equipment

Typical equipment specifications for Climate Zone 1A installations.

Heating Systems

Heat pump
Gas furnace (backup)
Electric resistance
Typical AFUE
80-90%

Cooling Systems

High-efficiency AC (16+ SEER)
Heat pump
Typical SEER
15-18 SEER

States in Climate Zone 1A

Climate Zone 1A covers 2 states across the United States. Click a state to see city-specific climate data and Manual J load calculations.

Florida
Hawaii

Frequently Asked Questions About Climate Zone 1A

Q1What states are in Climate Zone 1A?

Climate Zone 1A includes parts of Florida, and Hawaii. This zone represents a cooling-dominated climate with humid moisture conditions.

Q2What are the design temperatures for Zone 1A?

The official ASHRAE design temperatures for Climate Zone 1A are:

  • Winter 99% Design Temp: 44°F
  • Summer 1% Design Temp: 94°F
  • Summer Wet Bulb: 78°F

Q3What equipment works best in Climate Zone 1A?

For Climate Zone 1A (Very Hot - Humid), recommended HVAC equipment includes:

Heating Systems:
  • • Heat pump
  • • Gas furnace (backup)
  • • Electric resistance

Typical AFUE: 80-90%

Cooling Systems:
  • • High-efficiency AC (16+ SEER)
  • • Heat pump

Typical SEER: 15-18 SEER

Q4What R-value insulation is required in Zone 1A?

IECC 2021 requires the following minimum R-values for Climate Zone 1A:

Walls
R-13
Roof
R-30
Floor
R-13
Window U
0.4

Q5Is Zone 1A heating-dominated or cooling-dominated?

Climate Zone 1A is cooling-dominated. This means cooling loads typically exceed heating loads, requiring greater focus on AC capacity, SEER ratings, and moisture control.

Q6What is the moisture regime for Zone 1A?

Zone 1A has a humid moisture regime. This means high humidity levels, significant dehumidification requirements in summer, and careful attention to latent cooling loads in Manual J calculations.

Get Accurate Load Calculations for Zone 1A

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