My question is this. For a super energy efficient home, can I size the mini splits for the entire house size- ie TWO 12K BTU units and just put one in the hallway upstairs and one in the basement hallway and assume the heat/ac flow will migrate naturally into the bedrooms/bathrooms. Or do I need one unit in each bedroom/bathroom???? Or perhaps put them in one bd upstairs and one bedrm downstairs and leave the doors open???
BACKGROUND: I am building a home in Historic Baltimore (only the front brick wall stayed--even the foundation was redug--so its new construction). I need to make decisions regarding the heating and air conditioning system but have run into difficulties determining the best system because of the unusual aspects of my home. I'm hoping someone here can shed some light on this. Basically i'm wondering how many and where i have to put minisplits if i go that route.
-3 levels (including finished basement with bedroom and bath in basement)
-10' wide ( yes you read correctly-my entire house is only TEN feet wide) by 38' deep (basement only 10' wide by 27'deep)
-sq footage approx 1000
-2bd 1 bath upstairs
"open" first floor
-party walls are "conditioned"- ie people live in the houses next door and heat/cool them so i'm assuming almost no heat loss or gain from 38' walls.-
-front and back walls 10' by 18' are R-19. Roof is R-38
-heat gain/loss (3) front triple pane low e argon EE windows 30”x48” in the front and two same in the back (plus French doors)
Everything I can find for minisplits says you need one per room—but my rooms are only 100-130 square feet that putting the smallest mini splits in each bedroom and one on the open main floor ((3) 9K BTU- bd rooms, 12BTU main floor) would still be completely oversized for my house size –especially considering it will be approx 50-70% more efficient than most homes due to size, high insulation, and little heat loss/gain from majority of exterior walls (party walls).
The alternative is a heat pump for heat/ac ducted to all the rooms but I have low (7’) ceilings in many parts of the home and its only 10’ wide so I really don’t want to waste the space to ductwork. I also read mini splits were 20-30% more efficient then a similarly efficient heat pump due to no losses in ductwork—and with Electricity rates at 14 cents/kwhr I definitely want to put the MOST efficient system in!
Thank you so much for any insights on this.