[LeRoySmith]

Originally Posted by ehonour

Ton80 has it mostly right. His definition of dewpoint is correct.

However, a dewpoint number makes no sense at all unless you also know the actual temperature, because what matters is the difference between temperature and dew point. If the difference is zero, as in his example (i.e temp=60 deg and dp=60 deg), then you have water condensing on surfaces. In that condition, the relative humidity is 100%; the air is holding all the water it can possibly hold.

You can have temperature of 105 deg and dewpoint of 80 deg and still feel very dry, with the sweat rapidly evaporating from your skin. (RH of 46%) Or temp of 40 deg and dewpoint of 40 deg and feel oppressively humid. (RH of 100%)

What matters for comfort is relative humidity, not dewpoint.

Concerning the OP question, an indoor RH of over 70% is pretty high. It's not yet mold territory, but something's not right.

I believe you are correct. Most of my education in this area was to keep machines happy but your explanation lines up with everything I learned.