Climate ZonesZone 4B

Climate Zone 4B: Mixed - Dry

Mixed climate with low humidity, warm summers and cold winters. Significant heating and cooling needs.

Load Characteristic
Balanced Loads
Moisture Regime
Dry
States Covered
4 States

ASHRAE Design Temperatures

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

Winter Design Temp
3°F

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

Summer Design Temp
92°F

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

Wet Bulb Temp
62°F

Summer wet-bulb for latent cooling load and dehumidification calculations

2021 IECC Insulation Requirements

Minimum insulation and window specifications for Climate Zone 4B 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: Dry

Low humidity climate with minimal moisture concerns

Key Considerations for Dry Climates:

  • Minimal dehumidification needed
  • Focus on proper humidification in winter
  • Lower infiltration moisture loads

Recommended HVAC Equipment

Typical equipment specifications for Climate Zone 4B installations.

Heating Systems

Gas furnace (92%+ AFUE)
Typical AFUE
92-96%

Cooling Systems

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

States in Climate Zone 4B

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

Arizona
Colorado
New Mexico
Utah

Frequently Asked Questions About Climate Zone 4B

Q1What states are in Climate Zone 4B?

Climate Zone 4B includes parts of Arizona, Colorado, New Mexico, and Utah. This zone represents a balanced climate with dry moisture conditions.

Q2What are the design temperatures for Zone 4B?

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

  • Winter 99% Design Temp: 3°F
  • Summer 1% Design Temp: 92°F
  • Summer Wet Bulb: 62°F

Q3What equipment works best in Climate Zone 4B?

For Climate Zone 4B (Mixed - Dry), recommended HVAC equipment includes:

Heating Systems:
  • • Gas furnace (92%+ AFUE)

Typical AFUE: 92-96%

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

Typical SEER: 14-16 SEER

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

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

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

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

Climate Zone 4B 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 4B?

Zone 4B has a dry moisture regime. This means low humidity levels, minimal dehumidification requirements, and focus on proper winter humidification to prevent dry air issues.

Get Accurate Load Calculations for Zone 4B

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