for years I have used the waste heat,, built a 20 x 20 in box and use a high micron furnace filter,, to trap lint / dust,, have a moisture meter in the base ment, and it never goes above 50 % in the winter,, up it's - 15 C outside now as I write,, has been some debate on the soap used in washing, but the rinse cycle is always used,, Grandkids get skin rash if soap is left in ,, so far so good, up stairs the humidity is 55% and the piano is still in good tune,, in summer I use the solar powered widget.