My exhaust air is going to the cold outside. How can I tell if condensation will form?
Condensation forms when moist air is cooled below the point where the air can still maintain the amount of moisture in gas form. The point at which humidity hits 100% is known as the “Dew point”. Any excess moisture will revert back to liquid (or solid) form and you will see condensation or fog. Again, RHCalc makes finding this point easy. Assume you have exhaust air that is at 85F and with an RH of 60%. Enter these two values in the first column. Since you don’t care about changing temperatures, just ignore the second column and click ‘Calculate’. You will find that the dew point is 70 degrees. If you are expelling air into an area where the temperature is at or below this value, you will see fog. If you have a wall surface that is at or below this temperature, water droplets will condense on it and you will get runoff. Keeping your exhaust above the dew point keeps it in vapor form and invisible to normal sight.
