Hi, Brains,

Your inquiry is about ductless HVAC. Ductless mini-splits would satisfy the "ductless" requirement, but they don't provide any ventilation (the "V" in HVAC.) And, like any air conditioner, they only dehumidify when running in air conditioning mode. Heating and cooling loads tend to be small in a basement so run time of any system will likely be short. I recommend a dedicated dehumidifier which may be all that's called for most of the year. And you'll need ventilation to bring fresh air into the space (some dehumidifiers have built in fresh air ventilation options.) For basements with conditioned living space, we typically install ducted mini-splits with an integrated dehumidifier and fresh air ventilation. I suggest you consult with a local HVAC design professional before you spend money on a system that's not right for your application.

I have never needed AC in my walkout basement even with huge windows . So not sure if you need it either . I live where summers are hot 35 c is pretty normal where are you and that IMO will make the answer easier.