The dry and itchy skin, the deep cracks in your feet, the hangnails that won't go away; all of these are a result of living inside in warm houses when it is cold outside. That's right; the reason our skin dries out in winter is not the cold outside, it's what happens to that cold air when we bring it inside. Typical early winter conditions would be for the temperature to be 20 degrees, the dew point 10 degrees, and the outside relative humidity 65%. When that air is brought inside and heated to 70 degrees, the relative humidity drops to less than 10%.
When the outside air is 10 below and the dew point is 20 below, the relative humidity works out to 60%. Bring that air inside and heat it to 70, and the relative humidity drops to less than 3%. This is why our skin feels so much better when indoor air is humidified during winter weather.
