Climate ZonesZone 4A

Climate Zone 4A: Mixed - Humid

True mixed climate with hot, humid summers and cold winters. Equal emphasis on heating and cooling.

Load Characteristic
Balanced Loads
Moisture Regime
Humid
States Covered
11 States

ASHRAE Design Temperatures

Official design temperatures for Climate Zone 4A per ASHRAE Fundamentals 2021. These values are critical for accurate Manual J load calculations.

Winter Design Temp
13°F

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

Summer Design Temp
91°F

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

Wet Bulb Temp
75°F

Summer wet-bulb for latent cooling load and dehumidification calculations

2021 IECC Insulation Requirements

Minimum insulation and window specifications for Climate Zone 4A 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-49

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: 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 4A installations.

Heating Systems

Gas furnace (90%+ AFUE)
Heat pump
Typical AFUE
92-96%

Cooling Systems

AC (14-16 SEER)
Heat pump
Typical SEER
14-16 SEER

States in Climate Zone 4A

Climate Zone 4A covers 11 states across the United States. Click a state to see city-specific climate data and Manual J load calculations.

Delaware
Kansas
Kentucky
Maryland
Missouri
New Jersey
North Carolina
Oklahoma
Tennessee
Virginia
West Virginia

Frequently Asked Questions About Climate Zone 4A

Q1What states are in Climate Zone 4A?

Climate Zone 4A includes parts of Delaware, Kansas, Kentucky, Maryland, Missouri, New Jersey, North Carolina, Oklahoma, Tennessee, Virginia, and West Virginia. This zone represents a balanced climate with humid moisture conditions.

Q2What are the design temperatures for Zone 4A?

The official ASHRAE design temperatures for Climate Zone 4A are:

  • Winter 99% Design Temp: 13°F
  • Summer 1% Design Temp: 91°F
  • Summer Wet Bulb: 75°F

Q3What equipment works best in Climate Zone 4A?

For Climate Zone 4A (Mixed - Humid), recommended HVAC equipment includes:

Heating Systems:
  • • Gas furnace (90%+ AFUE)
  • • Heat pump

Typical AFUE: 92-96%

Cooling Systems:
  • • AC (14-16 SEER)
  • • Heat pump

Typical SEER: 14-16 SEER

Q4What R-value insulation is required in Zone 4A?

IECC 2021 requires the following minimum R-values for Climate Zone 4A:

Walls
R-20
Roof
R-49
Floor
R-19
Window U
0.32

Q5Is Zone 4A heating-dominated or cooling-dominated?

Climate Zone 4A 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 4A?

Zone 4A 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.

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