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Minisplit choice

soarak | Posted in Energy Efficiency and Durability on

I am finishing the attic in Southern New Hampshire, 800 sq feet, with very good insulation and 4 windows.
I had a few contractors come in and giving me quotes for mini splits. None of them did any heat loss calculations. Most proposed 2 heads totalling 24k BTU. I did Manual J calculations and came with a number around 8.0k, which probably is still overestimated by a touch.

So the system I am after is 9k, single head, either positioned above the window to blow along the longest dimension of the room, about 38 feet, or floor unit positioned in the middle of the room blowing along the short dimension of the room, about 20 feet. I feel the floor unit might be able to distribute the heat a little better, considering it needs to blow shorter distance to reach all places, while the over the window unit will have a long way to blow (38 feet). Not sure which position would provide greater comfort.
It seems the over the window units are a tad more efficient.

My second question deals with brand. I am looking at either Mitsubishi or Fujitsu. My contractor, different than the other equipment pushers, will install the unit I want. I am thinking the Fujitsu might be a bit more efficient in really cold weather. I am predominantly concerned about heating. 
Any data would be appreciated. Andrzej

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  1. Patrick_OSullivan | | #1

    > I am finishing the attic in Southern New Hampshire, 800 sq feet, with very good insulation and 4 windows.

    The lack of quantitative data here makes things difficult. :-)

    Based on personal experience, like you said, 8,000 BTU/h is still probably high if it's truly "very good insulation". Floor unit seems like a good compromise to provide mixing of air. I've thought similarly for a similar install I'm thinking of in my own home.

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