What is the minimum height above a flat roof for a vent that is 8 feet away from a building that is 4 feet taller?

To determine the minimum height of a vent located on a building that is 4 feet taller than the flat roof it is venting away from, you need to consider the regulations regarding vent height in relation to building features to ensure proper venting.

In scenarios like this, the relevant code typically requires that the vent must extend vertically above the roofline. Specifically, the vent should be a minimum height above the flat roof equal to the distance from the vent to the nearest building plus a defined vertical clearance. In this case, since the vent is 8 feet away from a building that is 4 feet taller than the flat roof, the vent must extend above the roof by at least that difference in height.

The calculation would imply that the vent should be at least 4 feet (the height difference) plus an additional height requirement to ensure efficient air flow and prevent backdrafts, which is generally accepted as a total of at least 6 feet above the flat roof surface.

Therefore, the choice indicating that the minimum height should be 6 feet above the flat roof properly addresses both the height difference and the additional clearance needed for safe vent operation.