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Community and Q&A

Conditioning a basement in a superinsulated home?

Jesse Lizer | Posted in Mechanicals on

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).

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  1. Jerry Liebler | | #1

    What are you planning for ventilation? If you are using a ducted ERV or HRV it will distribute the heat quite effectively. Look closely at the Mitsubshi specs for the various capacity units and you'll find that the largest 'throtles' to the same minimum capacity as the smallest. The largest is only about $200 more than the smallest. To me this means that if you choose to use 2 they may as well both be the biggest.

  2. Jesse Lizer | | #2

    ducted HRV.

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