Gary Thorsen stood on a weathered wooden step stool, the metal tab of his Stanley tape measure biting into the fresh drywall of a room he intended to transform into a home gym. It was a , the kind of quiet hour where a homeowner’s ambitions often outpace their actual engineering requirements, and Gary, who had spent the last bookmarking fourteen different tabs of HVAC forums, felt a surge of quiet superiority over what he considered the “average” buyer.
He had read the cautionary tales about short-cycling and the humidity traps of oversized units, yet as he scribbled “22 by 15” onto the back of a drywall scrap, he was already mentally rounding up his BTU needs, certain that his extra hours of Googling had granted him an immunity to the very mistakes he was currently repeating.
There is a specific kind of psychological safety we feel when we “do our homework.” We believe that data is a shield. If the industry statistic says that a staggering number of ductless systems are sized incorrectly-either by well-meaning DIYers or by contractors looking to upcharge-we assume that statistic is a net woven for the uninformed.
We believe our diligence is the variable that changes the outcome, failing to realize that overconfidence in one’s own research is the very engine that keeps the failure rate high. Gary wasn’t just measuring a room; he was participating in a ritual of self-assurance that almost always ends with a unit that clicks off too soon, leaving the air heavy, still, and stubbornly damp.
I understand this because I have been Gary. Before I became an advocate for elder care and spent my days worrying about the thermal safety of ninety-year-olds, I was a man who believed he could out-math the laws of thermodynamics in my own basement.
The Parched, Vibrating Kiln
I once purchased an industrial-grade dehumidifier for a crawlspace that was, in retrospect, roughly the size of a large closet. I had calculated the cubic footage, factored in the local humidity of a coastal summer, and decided that the “recommended” model was for people who didn’t understand true moisture problems.
I bought the bigger one. I spent $1,140 on a machine that didn’t just dry the air; it turned the basement into a parched, vibrating kiln that shook the floorboards of the kitchen above. I had researched myself right into a mistake that cost me three times the necessary price and double the electricity bill. I thought I was the exception. I was, in fact, the textbook example.
The price of a machine that turned a crawlspace into a kiln-double the electricity, triple the cost.
This “Exception Bias” is particularly dangerous in the world of mini-splits because the technology feels deceptively simple. You find a unit, you match it to a square footage chart you found on a random blog, and you click buy. But a room isn’t just a square on a map. It’s a dynamic envelope of heat gain and loss.
Gary’s gym, for instance, had two south-facing windows and a ceiling that vaulted to eleven feet, a fact he tucked away in a subordinate clause of his mental notes rather than placing it at the center of his calculation. He was using the square-footage shortcut-the very thing he’d read was a “rookie mistake”-but he was doing it with intensity, which he mistook for accuracy.
Earlier that morning, I had finished a task that usually brings me a strange sense of peace: I matched every single one of my socks. There is a profound, if somewhat neurotic, satisfaction in seeing forty-two identical pairs of black cotton socks lined up in a drawer.
It represents a world where everything has its place and every problem has a direct, symmetrical solution. We want our HVAC decisions to feel like matching socks. We want the BTU count to snap into place against the room size with a satisfying click. But home comfort is messier. It’s more like a drawer full of mismatched wool and nylon, where the “correct” pair depends entirely on whether you’re hiking a mountain or sitting at a desk.
When we talk about the wrong-size statistic, we are usually talking about over-sizing. There is a deep-seated American impulse that says “more is better.” If a 9,000 BTU unit will cool the room, an 18,000 BTU unit will cool it faster, right? Wrong.
To do that, the coil needs to stay cold for a sustained period. When Gary installs a unit that is too powerful for his gym, the machine detects the temperature drop within four minutes and shuts off. The air is cold, but the water is still there. He ends up in a “cold clammy” box, wondering why his “carefully researched” system feels like a locker room at a public pool.
From “Thinking” to “Verifying”
The conviction of being the exception is what prevents us from seeking a second opinion. If you believe you’ve already found the truth, why would you ask someone to verify it? This is where the gap between the “Smart Buyer” and the “Successful Homeowner” widens.
The successful homeowner is the one who realizes that their of forum-skimming cannot replace the institutional knowledge of people who see these systems fail every day. The real verification happens when you step away from the forums and consult a curator like
where the goal isn’t just moving boxes, but ensuring the 18,000 BTU unit actually fits the 18,000 BTU need. It’s the transition from “I think I know” to “I have verified.”
In my work with the elderly, the stakes of this bias are significantly higher than a clammy gym. I’ve seen families install massive units in their aging parents’ bedrooms, thinking they are providing the “best” comfort money can buy. They want the room to be a sanctuary.
The family, certain they were being diligent, created a problem that didn’t exist before, all because they refused to believe they could be wrong about “more” being “better.” We often treat the “average buyer” as a fictional character, a straw man who doesn’t read the manual and buys the first thing he sees on an end-cap at a big-box store.
We distance ourselves from him to protect our ego. But the average buyer is just anyone who relies on a shortcut while convinced they are using a secret path. The “Square Footage Shortcut” is the most popular of these paths. It’s easy. It’s clean. It feels like matching socks. But it ignores the R-value of your insulation, the shade of the oak tree in your front yard, and the fact that you live in a climate where the humidity sits at 84% for most of .
The 31% Volume Problem
The irony is that the information required to get it right is usually right in front of us, but we filter it through our desire to be “done” with the task. Gary, standing on his stool, knew that his vaulted ceiling added about 31% more air volume to the room. He knew it.
But his brain, tired from the research and eager for the “win” of the purchase, whispered that the 12,000 BTU unit he liked-the one that was on sale-would “probably be fine” because he was a “diligent researcher.” He was using his expertise as a license to ignore his own data.
You have to accept that your Google-fu is not a substitute for a Load Calculation. You have to be willing to be told that the unit you’ve spent three nights dreaming about is actually the wrong choice for your specific wall. True diligence isn’t about how many tabs you have open; it’s about the willingness to hand those tabs over to someone who knows how to read the fine print between them.
When I finally admitted my dehumidifier mistake, I had to swallow a significant amount of pride. I had to list the unit on a local marketplace for $400, taking a $740 loss just to get the vibration out of my kitchen. It was a tax I paid for my own arrogance.
Now, when I help a family set up a cooling system for a senior, I don’t start with the BTUs. I start with the room’s orientation, the height of the windows, and the specific ways the air moves. I stopped trying to be the exception and started trying to be the person who gets it right.
The Descent
Gary eventually climbed down from his stool. He looked at his drywall scrap, then at his phone, then back at the wall. For a moment, he wavered. He thought about the humidity. He thought about the short-cycling.
Then, he shook his head, convinced that he had accounted for everything that the “average” guy would miss. He pulled the trigger on the oversized unit, unaware that he had just become the most predictable number in the industry’s annual report.
He felt like a winner, right up until the moment the compressor kicked in, the room turned cold, and the air stayed wet.