Loving My Minisplits
Comfort is relative — so you can use your ductless minisplits a little or a lot
Last year, still living in my little cottage due to delays and problems attempting to build a new house in my historic district, I finally got tired of the old gravity floor furnace and window air conditioners and decided to spring for a new HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. system. I looked briefly at installing a central ducted system, but I realized that I had really enjoyed the zone control that the window units had afforded me.
My cottage is moderately well insulated and air sealed for an almost 100-year-old house. At only about 750 square feet, the house has a total load of only about 1.5 ton. I looked at high-performance ducted heat pumps, standard gas furnaces, and both ducted and ductless minisplits.
I ultimately selected Mitsubishi ductless models because they would give me the same zone control I had with my window units, and they were the most efficient equipment available (rated at 26 SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. and 10 HSPF). I installed three separate units, each with its own outside condenser, instead of a single large condenser for all three interior units.
Interestingly, there was almost no cost difference between the single and multi-head systems, and the one-to-one models have a higher rated efficiency.
Making good use of high-performance equipment
Although it may not seem so compared to some of the world-class energy geeks who inhabit this site, I get pretty deep into the weeds when it comes to managing my HVAC systems. Even here in the sunny South, I don’t use my air conditioning very much, preferring to open windows and doors when the temperature and humidity are manageable, then closing the house up as the day heats up.
I often don't turn on the AC until late in the afternoon, and then usually turn it off again and open things up as the outside temperature goes back down. This has worked well through most of the year, although there are some days in July and August when the house stays closed up most or all of the day.
I have the luxury of working at home most of the time, so I can track the temperature, turn things on and off, and open windows as necessary, and I can dress as lightly as I want in order to stay comfortable. Even my only moderately well air sealed house tends to hold the temperature and humidity fairly constant when closed up. This wouldn’t be the case if I lived in Minnesota or some other insanely cold place, but it’s pretty moderate most of the time down here in Georgia.
You keep it how warm?
Some people, especially Southerners who have become accustomed to full-time air conditioning, can’t believe that I keep my house at about 80° to 82°F (and, occasionally, even higher) for most of the summer. I work and sleep under a ceiling fan, and I now find that I feel almost cold when the air conditioning is running full-time.
I feel particularly smug (not a challenge for me) when my windows are open on a beautiful day or night, and can hear my neighbor’s heat pump running – in both the winter and the summer. I can’t imagine what they are spending on their energy bills.
When I have guests, I usually set the temperature to a more socially acceptable level, and if I didn’t live by myself, I would probably have to make some changes. But, for now, at least, I have the “luxury” of being an energy curmudgeon and keeping the house warmer and colder than most people would accept.
- Carl Seville
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