Again I say in a properly built (Tight) house there should be no need to add moisture to the inside air. The problem should be getting the humidity down to a working level. If one need to add moisture to maintain a proper level (In the wintertime in cold climates, that is probably 30% to 35% RH, any more and your windows are dripping), ones money is best spent sealing the house. This also involves the health on the people in the house as the moisture exiting through the leaks is probably condensing in the structure giving molds and such a place to grow. When the wind changes, all those nasty things are entering your house the same way the moisture first left.