The vent in a high-efficiency furnace should slope in what direction?

The vent in a high-efficiency furnace should slope down toward the furnace. This is crucial for proper drainage of condensate, which is a byproduct of the combustion process in high-efficiency units. These furnaces extract a significant amount of heat from the flue gases, which results in condensation. If the vent were to slope upward or remain horizontal, there would be a risk of improper drainage, leading to moisture buildup in the venting system. Over time, this could cause corrosion, blockage, or even hazardous situations due to venting failures. By sloping the vent down toward the furnace, condensate is directed back to the furnace where it can be properly managed, ensuring safe and effective operation.