Which of the following is NOT a cause of cracks in foundation walls?

High temperatures do not typically lead to cracks in foundation walls, making this the correct choice. Foundation walls are primarily affected by physical forces and environmental conditions that directly cause stress or movement within the ground or the structure itself.

Shrinkage is a common cause, particularly in concrete foundations that can contract as they cure, leading to cracking. Differential settling occurs when different parts of a building settle at varying rates, often due to soil conditions or changes in moisture content, resulting in stress and cracks. Heaving, which refers to upward movement due to expanding soil (often from freeze-thaw cycles) or other forces, can also cause cracks as the foundation shifts.

In contrast, high temperatures can influence the building materials' expansion but do not directly cause the structural issues related to foundation cracking like the other options do. Therefore, selecting high temperatures as the answer identifies a factor that does not inherently cause foundational cracking.