Hey Ed, Does the air contain less moisture, even though the relative humidity goes up after the air moves across the evaporator coil?

In this edition of “Hey Ed,” Ed discusses relative humidity across evaporator coils.

Hey Ed, does the air contain less moisture even though the relative humidity goes up after the air moves across the evaporator coil? This is a very common misconception and the key word in all this is "relative." A better metric would be to use dew point, but people don’t typically do it. So when we look at the relative humidity of the air coming out of a supply vent, the relative humidity is higher than the air going into the return. But the air coming out of the supply is colder. Let’s call it what it is. The boxes, the CFM, are smaller so they can’t hold as much moisture, which equals a higher relative humidity. If you really want to look at moisture content, look at dew point, or another way to do it is determine how many grains of moisture each pound of air holds. And with that, we’ll never ask this question again. We simply know how much moisture a sample of air holds. And that’s the way I see it.