Why are steel roofs and aluminum vents considered a bad match?

Steel roofs and aluminum vents are regarded as a bad match primarily due to the potential for a galvanic reaction. When two different metals are in contact with each other in the presence of an electrolyte, such as moisture, an electrochemical reaction can occur. This reaction can lead to accelerated corrosion of one of the metals involved. In this case, aluminum is more likely to corrode when paired with steel, particularly if the steel is galvanized, further increasing the potential for corrosion due to the differing electrical potentials of the two metals.

Understanding this interaction is crucial for home inspectors because it can significantly impact the longevity and performance of the roofing system. Inspectors should be aware of the materials used together in roofing assemblies to prevent future structural issues related to corrosion that could compromise the integrity of the roof and its components.