Hmm, I think I should put this as its own post.
I own a DEhumidifier! In addition I keep the AC running, never the heater. Ever.
The AC will dehumidify your house, and a dehumidifier does that specifically. Cold air is good for your lungs because it kills bacteria/slows growth. Dry air is good for your lungs because it slows bacteria growth.
If you are lucky enough to live in cold climate, then wear wonderfully comfortable polar fleece and keep your house at a beautiful 40-60 degrees!!!
I live in texas and like to cool my house to 65 for the reasons mentioned above.