RE: Low temp, high humidity?

Can someone please explain the correlation between low temperatures inside a residential home and high humidity. I was told to lower the temperature inside the higher humidity, Which seems to be true. But I don’t know how to explain that to homeowners. Example today tstat set for 64, temp inside 66 humidity inside 92%.

Add Comment
4 Answers

To add to OnPoint, yes the colder temperature cannot hold as much moisture so running the tstat lower forces that moisture to condense out which does lower the grains of moisture in the air. In this particular example, with a indoor dry bulb of 66 F and 92 % humidity the dew point is 64 F which is exactly what your tstat is set for. Meaning, the supply air will condense out water vapor at the coil and through the ducts as long as it is below 64 F which ultimately reduces the humidity in the conditioned space.

HVACRamjet is also correct that dry bulb tstat set-points are pretty meaningless in humid environments. Really, a persons comfort level is dependent on the enthalpy (fancy word for energy in BTU/lb) content of the air more than it is just the dry bulb temperature and the enthalpy content is a function of temperature and humidity. As a general rule, a dew point of 60 F is comfortable for most people and once it gets above 65 F things start getting “muggy” and uncomfortable (probably another reason why the set-point of 64 is comfortable here because you’re 100% RH at the set-point and the dry bulb temp = wet bulb = dew temp). I hope that makes sense.


Rookie Answered on August 21, 2018.
Add Comment

Your Answer

By posting your answer, you agree to the privacy policy and terms of service.