If you've traveled out of country, you've definitely seen those funky air conditioners/heaters mounted on the walls of apartments in, say, France, or somewhere in Asia. Those with a curious mind may also wonder how they work. I know I did when I first encountered one in a vacation rental in Provence. It wasn't a window unit, so there was seemingly nowhere for any air to draw from.
But HVAC systems not exactly being my primary concern while eating my way across France, I didn't give it much thought.
First, My Own Experience
Fast forward a few years to our purchase of a big old Victorian home with no central air. My husband and I live in Kentucky, near the Ohio River where the combined heat and humidity in the dead of August is the equivalent, I've once read, of wrapping yourself in a hot, damp wool blanket. Stretches of murderously hot triple-digit temperature days aren't uncommon. A/C was Priority Number One, and I was intrigued enough by those so-called split systems, a.k.a. mini-splits, a.k.a. ductless systems, that we got a quote: For one floor alone of the three-story house it was nine grand. Um, nope. We went with traditional central air for the main house (first two floors) and still supplement with the ugly-but-effective window units the previous owner permanently built into a couple of second floor windows.
But when it came time to choose a heating and cooling system for the third floor—an apartment we planned to rent out through Airbnb—we looked at mini-splits again. Because it meant we wouldn't have a furnace closet eating up limited floor space, and since I'd heard so much about how energy efficient they were, we ponied up $6,000 for a Daikin system the local contractor recommended.
I. Hate. It.
Words cannot express my loathing of this thing. It first died on a zero-degree Christmas Eve, leaving our Airbnb guests without heat for days on end. And when you live and die by reviews, if you can't get your space as cool as a cucumber when it's 99 degrees outside, or warm enough to overcome frigid temps, you won't be in the vacation rental business very long. Since the beginning, I've been mired in fallout related to system defects and sub-par installation. I massively regret the decision.
Mind you, that doesn't mean mini-splits are wrong for you. Prior to getting ours, I'd heard only rave reviews, and, even though this was the most expensive part of the project, I admittedly didn't do due diligence before pulling the trigger. Plus, I picked the only contractor that knew how to do them (to my knowledge)—a guy who came recommended by someone I didn't think would steer me wrong. I thought wrong.
So I'm here to share everything I wish I'd known when I made this decision, and hope you can make the right call for your space. Francis J. Dietz, the vice president of public affairs for the Air-Conditioning, Heating, and Refrigeration Institute, or AHRI, answered my every last question, and sent me to a helpful website. (If only I'd called him a year ago!)
What is a Mini Split System?
Ductless mini-splits are a two-part system that can heat or cool individual rooms or areas of your home. One, there's an outdoor unit with a compressor (that's the part of an air conditioner or heat pump that compresses and pumps refrigerant into the home), and a condenser coil (that's the part that either releases or collects heat, depending on the time of the year.)
Inside you have one or more units mounted on walls that blow out heated or cooled air. (If you want the technical explanation: the refrigerant is drawn across an evaporator coil which removes humidity and cools the air, or heats the air, and then a built-in fan pushes that air into the room.)
What you typically don't see is a tube running between the indoor and outdoor units. That tube snakes its way inside your walls. (Unfortunately in my case I learned too late that the tube wouldn't fit, so it was exposed in some parts.)
Mini Split Myths
So I'd heard over and over that mini-splits are more efficient, a big reason being that there's no loss of air as it travels through ductwork. I was never able to track down an original source for those numbers (I heard they were 30 percent more efficient), but it sounded good.
According to Francis, though, that's not true at all. "For a typical sized American house in, say, the mid Atlantic or southern states," he said, "[I don't think] that it's any less efficient to have a central unit where the air comes out of register." He hadn't heard that 30 percent number, and said he doesn't hear people in the industry talking about them being more efficient either.
Zoning is the other big advantage. And it sounds great–why heat or cool anything other than the room you're in (especially in a monster like ours!)? According to Francis, though, you don't need mini-splits for that. (He sent me to Zonefirst, a system you can retrofit to existing central air and furnace systems, which I plan to look into for our first two floors.) So far, two strikes against mini-splits.
Then Why Buy One?
Maybe the question is more 'Why don't most people need them?' Most homes in the United States, with the exception of in the North/North-East, were built with forced air furnaces, Francis explained. When it comes time to add cooling to homes with such systems, the options are central air that uses the existing ductwork, less expensive but unsightly window units, or mini-splits. "Since I have ducts it wouldn't make sense for me to put in mini-splits," he said. "Why would I put things on my walls?"
But for anyone without ducted heat, it's going to be a more popular option. They are more efficient than a window unit, Francis said, and in places like Vermont or upstate New York, "It's a huge benefit because they now get to have A/C without one in each window." They're also popular for freestanding spaces like sheds, backyard studios, and garages.
I felt a little less bad about my buyer's remorse when Francis acknowledged it's difficult for a consumer to do this research. The first thing, he said, is "Start out with the right contractor."
Specifically, he added, "Look for one that has certified technicians." They're going to be much more proficient in sizing (or determining how much oomph your system needs). At minimum, he said, use someone recognized by the Air Conditioning Contractors of America (ACCA) or the Plumbing Heating Cooling Contractors Association (PHCC). Sadly, my (now former) contractor is not recognized by either.
Once you've gotten multiple quotes, "Have a good conversation with the contractor, and have them compare different technologies," he said. They're the experts after all. I failed there too, not asking nearly enough questions before I signed the dotted line.
A Few Final Thoughts if You Decide to Install One
- Make sure the tubing will fit in your wall or you'll end up scouring Pinterest for ways to cover it. I went with copper conduit to (hopefully) jive with an industrial/rustic look we have going on.
- Be prepared to use a remote control for each wall unit that was apparently designed by the person who designed original VCR remote. There are about 99 buttons that I don't even know what they do, and guaranteed somebody is going to lose or accidentally leave with one. I learned too late that the cost of an actual thermostat was a huge extra cost, let alone one that would be WiFi compatible. So I'm unable to help guests with climate control without physically intervening, and if they check out in the winter with the heat full blast (as many do) it continues ratcheting up our utility bill until one of us can get up there to turn it down. Because of all the trouble I've had with mine the manufacturer is giving me WiFi adapters which will let me control the system with an app which I think (hope!) will be a big help.
- Yes it's zoned in the sense that you can have different temperatures in different rooms but you can't have one on heat and one on cool if they're running on the same outdoor compressor. (Why would you even want to do that? Move into a house where it gets 10 degrees warmer with every floor you climb and you'll know!)
- You'll also need a thermometer if you get a system like ours. The remote control doesn't display the room temperature(!?!).
- In my experience (and that of two friends with the systems), they don't deal well with extreme temperatures. Our neighbor's mini-split (the same brand as ours, inherited with their home purchase) went out at the same time ours did over this past arctic winter… and her pipes burst from the cold. She promptly had a traditional furnace installed. Another friend who uses a mini split at her retail shop also lost heat. These are three situations I just happen to know about, so I can't say it's a trend. But it's certainly some coincidence.
So should you get a mini split system? Based on my personal experience, I steer friends away from it. But if you live in a region where you don't have a lot of other options, and if you do your research, and if you hire a proficient and trustworthy contractor, well, maybe you'll have a better experience than we did.