In what situation would the type of asphalt used be critical for performance?

The correct choice highlights the importance of selecting the right type of asphalt for roofs with a slope greater than 1:12. In this scenario, the asphalt's performance is critical due to the increased exposure to water runoff and potential erosion that can occur on steeper slopes.

On steeper roofs, the likelihood of water pooling is significantly reduced, but the impact of wind and precipitation can be more pronounced, which places greater demands on the roofing materials used. The asphalt must possess the necessary properties to withstand these stresses, including flexibility, UV resistance, and the ability to bond effectively with other components to prevent leaks or degradation.

While other roof types—like flat roofs—also require careful material selection due to factors like water ponding or thermal expansion, the performance of asphalt becomes particularly crucial in steeper applications. This is because the additional forces acting on the roofing system may not be as well compensated by materials that are not specifically engineered for these conditions. Therefore, ensuring that the right type of asphalt is used in these situations is key to maintaining the roof's integrity and durability over time.