We talk about Dew Point on commercial building inspections because it affects how certain systems function. But What id Dew Point?
The dew point temperature is the temperature below which the water vapor contained in the flue gas will turn into a condensate (a liquid). This is often referred to as condensation. For temperatures below the dew point temperature, moisture exists. For temperatures above the dew point temperature, vapor exists. If the chimney or venting material falls below the dew point temperature, condensation in the flue will occur. The dew point temperature can be measured if a technician sees indications of condensation occurring at a non-condensing appliance. The image below is an indication of condensation forming inside the flue pipe of a natural-draft furnace.