When installing valleys in areas prone to freeze-thaw cycles, which modification is most likely necessary?

When installing valleys in areas prone to freeze-thaw cycles, open valleys are often the modification chosen due to their beneficial properties in managing water flow. Open valleys consist of a channel that allows for better drainage, which is particularly important in regions where melting snow or ice can lead to excess water accumulation. The design of open valleys helps direct water away from the roofing materials, minimizing the risk of ice dam formation and ensuring that any water that does not drain quickly enough does not seep into the roof structure.

Additionally, the open valley design typically incorporates metal flashing, which offers added protection against leaks and enhances the durability of the roofing system in harsher climates. Metal is less susceptible to damage from freeze-thaw cycles compared to shingle valleys, where water can become trapped and potentially freeze.

In contrast, closed valleys, curved valleys, and flat valleys might not provide the same level of water management and drainage, making them less suitable for areas subject to these harsh climatic conditions. Such designs can lead to water pooling and increased susceptibility to damage over time due to ice formation.