Ductless mini-split air-conditioners have risen in popularity dramatically in recent years. One study now pegs their domestic market share at more than 40 percent compared to larger-scale HVAC units—and the smaller systems are even more popular in Asia and Europe than in the US. Mini-splits make a compelling climate control solution for a number of reasons. They are much smaller and easier to install than HVAC systems, they’re far less expensive, and they’re quiet. Many are sold at big-box stores and online, and enterprising DIYers can certainly install one without professional help, provided they have the required electrical connections. (Some mini-splits operate on 115 volts, but others require 220-volt wiring, which will likely mean a call to an electrician.) They’re also increasingly outfitted with smart features like mobile app support, tricks that you can’t do on HVAC units without a fancy thermostat.…