How does insulation behavior affect roof performance?

• A. Insulation has no effect on roof performance.
• B. Only thermal conductivity matters.
• C. Thermal drift and compressive strength matter under foot traffic.
• D. Insulation should be avoided in roofs.

Answer: (C)

Insulation affects roof performance through more than just heat flow. Temperature changes cause the insulation to expand and contract, which can create stresses, shift components, or open gaps in the roof assembly if the insulation moves relative to fasteners, seams, or the membrane. It also must resist compression from foot traffic and equipment; if it lacks adequate compressive strength, it can be crushed, reducing its thickness and R-value and potentially damaging the waterproofing layer. Because these mechanical and thermal responses influence energy performance, durability, and service life, considering both thermal drift and compressive strength is essential for a roof system. The other ideas miss this broader role: insulation does affect performance; focusing only on thermal conductivity ignores mechanical and dimensional effects; and insulation should not be avoided on roofs.