A lot of talk is about the exterior walls and roofs of superinsulated homes. Also R value is addressed for basements and below slabs. Conditioning of the main floor or above grade is often discussed and minisplits are recommended. However I cannot seem to find too much talk on conditioning a finished basement level for superinsulated homes.

I was contemplating what the temperature swings might be in the lower space. My original plan was to put a single head mini on the main level (1,600 sq ft) and a single in the basement. Now I am debating if I even need the single in the basement. Simply install some electric baseboards in the bedrooms and run a dehumidifier in the summer?

I was sitting in my current basement last night which gave me the idea. Its an old, cinder block basement that actually is open to the crawl space under a small addition added. There are old, single -ane top hinged wood windows at the rim board area. The ductwork runs across the exposed ceiling. There is 1 vent in the basement, but I have it closed off. It stays very comfortable in there year round. Because of this, I was thinking a new basement (ICF) would be even better.

The home is in zone 6, 7200 HDD with a main floor loss of around 16,000 BTU. My programs seem to be having a hard time on the basement heat loss. It’s giving me everything from 2,000 btu to 7,000 btu. I planned on using the new 21,000 Mitsubishi Hyper Heat head with a 2′ baseboard in each bedroom. The living/kitchen/foyer/dining is all open to each other. A natural gas fireplace would be the backup for this area.

I was thinking I would install the 9,000 BTU H2h head in the basement. Do you think this is needed? The basement does not have a door on it, but its also not an open staircase (walls around it, not railings).

The other option on the table is geothermal. I know most think it is way overkill for a superinsulated home with low heat loss, however a 2-ton system in my area, with local credits and tax credits, is only a couple thousand more then 2 minisplits and a couple baseboards installed. (total installed net cost is $10,500).