How high should exterior supply and exhaust termination hoods typically be installed?

The requirement for exterior supply and exhaust termination hoods to be installed at least 18 inches above grade or snow accumulation is essential for ensuring that these hoods function effectively and safely. This height helps prevent potential obstructions caused by snow, debris, or rainfall, which could impede airflow and potentially lead to backdrafting or pollutants entering the building.

Installing the hoods at this height also serves to minimize the risk of exhaust fumes being reintroduced into the building's intake air supply, which is especially important for maintaining indoor air quality. Additionally, it helps mitigate concerns regarding pests and animals that might find lower installations to be inviting.

While other options suggest different heights, they do not account for specific factors such as snow accumulation, which is crucial in many climates. Therefore, the choice of at least 18 inches is a widely accepted standard in the field of insulation and ventilation that promotes both efficiency and safety in the system's operation.