My home is a 1400 sq ft 1953 ranch, Zone 5a CT, on the low end of a hill, and always humid.  Currently, I have portable dehumidifiers in each “zone” – kitchen, living room, and bedroom hallway.  We have encapsulated the crawlspace in plastic sheeting – floor and cinder block walls – and have a SantaFe Compact 70 dehumidifier running full time.  The humidity is around 40% all year in the basement.  [We also excavated and installed a french drain around the crawlspace exterior, with a bitumous coating on the cinder block, Rockwool Comfortboard 80 over that.  The crawlspace has been dry since then, but we did have mold before all of that.] 

My HERS rater indicated that an ERV is recommended; research has led me to the Ultra-Aire Ventilating Dehumidifier, which I can modify (as recommended by the company) to include a fresh air intake.  See page 3:  https://www.santa-fe-products.com/wp-content/uploads/sites/4/2021/05/Santa-Fe-Ultra70-Alternative-Install-Guide.pdf

Also, I removed my ancient, non-working oil furnace and tanks (along with their ductwork; I kept the registers in each room), and am in the process of installing the MRCOOL DIY 27k BTU multi zone ductless mini split with air handlers in the living room (12k), kitchen (9k) and one bedroom (9k) (that directly faces the hall – the bedroom door will remain open most of the time).  The living room and entry/mudroom are open to one another, but closed to the rest of the house by doors leading to the hallway (that contains the bedrooms) and the kitchen. 

My questions:

The SantaFe Compact 70 that we have in the basement can be converted to a ducted dehumidifier.  Should I keep it where it is, as it is, since it is doing the job?  Or should I convert it into a ducted dehumidifier?  Will it then be a “ventilating dehumidifier”?

Since the Ultra-Aire Ventilating Dehumidifier allows for a No Existing Ductwork Installation and allows for fresh air intake, is this the way to go?  And accept that I’ll have TWO “whole house” dehumidifiers in my 1400 sq ft home?  Or do I purchase this one and sell the other? 

Once I do either of the above (or some other option that I am sure you have for me!), am I correct that the indoor air return should be in the living room, and the supplies should be in the bedroom hallway and kitchen (and, maybe, the entry/mudroom, adjacent to and open to the living room)?  I have a Panasonic WhisperGreen in the one bathroom [which will eventually be replaced with the WhisperWarm – the WhisperGreen will then be moved to the entry/mudroom that now houses a Miele Heat Pump W/D] and a range hood in the kitchen.

Possibly related – two of my north-facing windows (under the gable of the roof) smell strongly of mold, as does the HVAC register under one of them.  There was water intrusion on one window that I thought I had repaired.  The smell is very strong on the interior sill of one – could this be due to interior humidity?  Or am I dealing with mold that is most likely still in the wall and window frame (which wouldn’t be helped much by the ventilating dehumidifier)?   

Thanks!