I have a fairly large house with 3,300 sq feet on the main floor and a full basement below. The basement is basically completely open. I have a Comfort-Aire HRV070A1C00JRT geothermal unit. My insulation, including the attic, is Iconene open cell spray foam. The house is tight, but I have never done a blower door test. My AC is oversized as is my heat. (I'm going to have to live with it until a replacement becomes necessary). I generally run the fan full time for circulation, however the heat is only required for short periods of time. I also have an HRV. Occupants are myself and my wife with three little girls under 10 years old. My humidity today is 25%. Outside here, near Lafayette, Indiana it is 39 degrees with humidity of 73%. I realize I have a large house (10' ceilings in the basement, 9' upstairs 55,000 cu ft? or so), however it seems really hard to pin down what humidifier to purchase. We have high iron/lime in our water, however it ok after the water softener. I am in a rural area on a well. I am considering the Aprilaire 800 (steam) and the Honeywell TruSteam HM512VPIAQ, along with the Aprilaire 400 hooked to my hot water or the GeneralAire 1137. I know the Honeywell TruSteam is not rated at as high capacity as the Aprilaire 800, but, even though I have a big house, do I really need that large capacity as compared to a house which is not as airtight? I have an oversized geothermal AC primarily because my HVAC installer convinced me the foam wouldn't make such a big difference and simply sized it incorrectly. I point that out because my heat is also oversized and does not run as much as a "normal" unit. I could certain benefit from anyone who has tackled this problem or something similar before. Thank you so much!