Climate ZonesZone 8

Climate Zone 8: Subarctic

Subarctic climate with extreme cold. Maximum heating requirements, no cooling needed.

Load Characteristic
Heating-Dominated
Moisture Regime
Moist
States Covered
1 State

ASHRAE Design Temperatures

Official design temperatures for Climate Zone 8 per ASHRAE Fundamentals 2021. These values are critical for accurate Manual J load calculations.

Winter Design Temp
-42°F

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

Summer Design Temp
72°F

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

Wet Bulb Temp
60°F

Summer wet-bulb for latent cooling load and dehumidification calculations

2021 IECC Insulation Requirements

Minimum insulation and window specifications for Climate Zone 8 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-60

Minimum attic/ceiling R-value for energy compliance

Floor Insulation
R-38

Minimum floor R-value (over unconditioned space)

Window U-Factor
0.30

Maximum window U-factor (lower is better insulation)

Window SHGC
0.50

Recommended Solar Heat Gain Coefficient

Air Infiltration
0.15

Typical ACH (air changes per hour) for load calculations

Moisture Regime: Moist

Moderate humidity levels throughout the year

Key Considerations for Moist Climates:

  • Moderate dehumidification in summer
  • Balanced moisture control
  • Standard moisture management

Recommended HVAC Equipment

Typical equipment specifications for Climate Zone 8 installations.

Heating Systems

Gas furnace (98%+ AFUE)
Boiler
Oil furnace
Typical AFUE
97-98.5%

Cooling Systems

Not typically needed

States in Climate Zone 8

Climate Zone 8 covers 1 state across the United States. Click a state to see city-specific climate data and Manual J load calculations.

Alaska

Frequently Asked Questions About Climate Zone 8

Q1What states are in Climate Zone 8?

Climate Zone 8 includes the state of Alaska. This zone represents a heating-dominated climate with moist moisture conditions.

Q2What are the design temperatures for Zone 8?

The official ASHRAE design temperatures for Climate Zone 8 are:

  • Winter 99% Design Temp: -42°F
  • Summer 1% Design Temp: 72°F
  • Summer Wet Bulb: 60°F

Q3What equipment works best in Climate Zone 8?

For Climate Zone 8 (Subarctic), recommended HVAC equipment includes:

Heating Systems:
  • • Gas furnace (98%+ AFUE)
  • • Boiler
  • • Oil furnace

Typical AFUE: 97-98.5%

Cooling Systems:
  • • Not typically needed

Typical SEER: N/A

Q4What R-value insulation is required in Zone 8?

IECC 2021 requires the following minimum R-values for Climate Zone 8:

Walls
R-20
Roof
R-60
Floor
R-38
Window U
0.3

Q5Is Zone 8 heating-dominated or cooling-dominated?

Climate Zone 8 is heating-dominated. This means heating loads typically exceed cooling loads, requiring greater focus on furnace capacity and winter insulation values.

Q6What is the moisture regime for Zone 8?

Zone 8 has a moist moisture regime. This means moderate humidity levels, balanced moisture control needs, and standard dehumidification capacity sizing.

Get Accurate Load Calculations for Zone 8

Our AI-powered Manual J calculator uses official Zone 8 design temperatures and IECC requirements for pinpoint accuracy. First report is FREE.

Upload Blueprint → Get Free Manual J