How North Carolina’s Diverse Climate Shapes Building Material Selection | North Carolina Building Materials Supplier | Best Supply

North Carolina’s climate zones

The Tar Heel State spans three distinct climate zones as defined by the International Energy Conservation Code (IECC):

• Coastal and southeastern regions: Zone 3A, Warm-Humid (Warm-Humid)
• Central Piedmont and parts of the western region: Zone 4A (Mixed-Humid) 
• Higher elevations in the western mountains: Zone 5A (Cool-Humid)

The coastal and Piedmont regions (IECC Zones 3A-4A) experience humid summers with temperatures near 90 degrees (F), and mild winters with average temperatures between 50-60 degrees. In mountainous areas (Zone 5a), summer temperatures are cooler and winter temperatures can drop below zero.

Meanwhile, the state straddles five USDA Plant Hardiness Zones—from 9A in coastal areas to 5B in the mountains. Contractors must adapt to these climate conditions to prevent moisture damage, mold growth, energy loss and structural distress. (For more insight about temperature and moisture management, see related posts:

• Sorting Out Insulation Types and Their Properties
• Decoding the Terms and Materials Used to Manage Moisture.)

To manage these extremes, North Carolina building codes require different insulation R-values depending on the zone, according to insulation manufacturer RMax. The regulations align with IECC and International Residential Code (IRC) standards.

Moisture on the coast

Eastern NC sees an average of 40-56 inches of rain annually, with around 31 tornadoes and frequent thunderstorms, according to Wikipedia. High humidity also accelerates mold growth and wood decay.

In this climate, contractors need moisture-resistant materials such as:

• Weather-resistant barriers (WRBs) and house wraps to block intrusion
• Engineered lumber or naturally rot-resistant species like cedar or pressure-treated pine
• Exterior claddings such as fiber-cement siding or vinyl to inhibit moisture infiltration
• Proper flashing, gutters and grading to prevent water from standing or entering assemblies

In coastal areas, salt-laden air demands corrosion-resistant fasteners (stainless steel or hot-dipped galvanized) and metal trims rated for marine exposure.

Temperature swings in the mountains

In western North Carolina’s elevations, contractors must guard against freeze-thaw cycles and snow loads. That means:

• Masonry, stone veneers, concrete and brick must be rated for freeze-thaw resistance. Using high-quality sealants and air-entrained concrete significantly reduces cracking risk.
• Adequate roof pitch, robust underlayment and effective ice-and-water shields to protect against snowfall and ice dams. 

Hurricanes, storms and wildfires

With tropical storms and hurricanes impacting the eastern coast, especially during summer and fall, materials must meet wind uplift and impact resistance standards, including:

• Impact-rated shingles and siding to withstand hail and debris from storms.
• Reinforced fastening methods for asphalt shingles and metal roofing panels to resist uplift.
• Impact-resistant doors, upgraded header framing and robust anchoring systems for entrance areas.
• Class A fire-rated shingles ensure protection from embers during fire season.

Updated codes

The IECC climate zone map is updated every third year to reflect the evolving climate, according to the blog of Johns Manville, manufacturer of engineered materials including roofing and insulation. As a result, some counties in North Carolina have shifted zones over time. Contractors should always verify local code jurisdictions and check the 2018 North Carolina Residential and Commercial Energy Conservation Code, which specifies R-value thresholds, U-factors for windows/doors and mechanical efficiency criteria. (The 2024 update of this code was postponed and is expected to be made available in the second half of 2025.)

Requirements compared

North Carolina’s climate diversity means one-size-fits-all building approaches don’t work. To build durable structures that perform efficiently and meet project budgets, choose materials that meet the demands of the localized climate. 

The following chart offers an overview of requirements by IECC zone.