Just a spare room in my shop....8x13, 7' ceiling. Insulated, inside is OSB with a couple coats of aluminum mobile home roof coating to seal moisture inside. An OLD (use R-12, not R-22) window air conditioner on a shelf inside. Heat off the AC raises the room temp to about 130 max, moisture comes off as the temp raises, hits the cold coil and drips in a bucket ( basic dehumidification process).
I air dry my lumber down to about 18-20% moisture (year or more on sticks in dry), then move it into the kiln to take it down to 6-8% for furniture/cabinet projects.