Side Effects of Overheated Attics

Gus Koedding • June 8, 2025

Attic Temperature with Dark Composition Shingle Roof

When it's 90°F (32°C) outside and the home has a dark composition shingle roof, attic temperatures can skyrocket due to heat absorption and poor ventilation.

🔥 Expected Attic Temperatures:

  • Average attic temp under dark shingles: 130°F to 150°F (54°C to 66°C)
  • In some cases (poor ventilation or no radiant barrier): it can reach up to 160°F (71°C)

⚠️ Why It Gets So Hot:

  • Dark shingles absorb more UV radiation.
  • Heat radiates into attic space and gets trapped, especially if ventilation is poor.
  • Radiant heat gain continues into the evening even after the air temperature drops.

🚨 Side Effects of Overheated Attics:

  • Degraded insulation performance
  • Warped roofing materials
  • Increased cooling load on HVAC system
  • Higher risk of attic mold growth due to trapped moisture and condensation at night

🛠️ Pro Tip:

Installing attic ventilation upgrades, air sealing, radiant barriers, or blown-in cellulose insulation with proper R-value can help bring those attic temps down by 20–40°F.


https://www.insulationspokane.com/faq

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