Can I make mini splits more efficient at extreme temperatures?
I renovated a home in northern New Hampshire with meaningful air sealing and additional insulation. I installed Mitsubishi hyper heat mini splits upstairs and down, but have baseboard and wood stove backups for when the temperatures drop below 20f and the mini splits need help. Overall, I am happy.
My question is about the outdoor units. Below a certain outdoor temperature the mini splits lose some energy efficiency.
Would a passive solar box, insulated on sides and with a black concrete slab on top of rigid foam, south facing, containing the outdoor units preheat the outside air when temps get really cold? Would such an arrangement keep the mini splits at more efficient operating levels such that I would need less frequent use of my backup heat during December-march?
I suspect such a passive solar box would require some attention and I would have to open the glass in warmer months. Humidity inside the box and its impact on the unit would have to be considered. Cost would have to be considered, but building such a box does not seem technically difficult. But is this idea viable? If the outside air inside the passive solar box could be kept above 20f for a meaningful amount of time it seems like it could be helpful. A metaphorical turbo for the mini split?
Appreciate any thoughts!
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