The cost of keeping cool

How to choose the right air-conditioning system

ductless air conditioner
A ductless air conditioner head cools Erika Dodge’s upper floor. Submitted photo

Erika Dodge’s tidy 1.5-story Cape Cod-style home in Kenny has been in her family for nearly 70 years. After taking over the title, she redid the garish main-floor bathroom, gut-remodeled the kitchen, installed double-sliding glass doors with views of the spacious backyard and replaced a homemade retaining wall with tasteful landscaping.

Her latest project may have been her most ambitious. Eager to move her bedroom off the main floor, she added a dormer to the cramped half-story above, creating a full-floor master suite.

The only problem: As in so many older homes, the upper half-story was blazing hot in summer. Just one air-conditioning duct served the entire floor, not nearly enough to keep things comfortable on sticky nights.

“The way it was, I wouldn’t have moved the bed up there,” Dodge said.

After determining that there wasn’t enough space to extend the existing ducts, Dodge settled on a solution: a ductless mini-split air-conditioning system. In such a small space, she’d need just one head — the interior unit — connected to a small outdoor condenser by a three-inch-diameter bundle.

The installation took a single afternoon; Dodge had fretted about a destructive, disruptive slog, but she barely noticed the crew at work.

When the crew left, she had reliable summertime cooling and dehumidification, enough heating power to ward off November’s chill and a neutral fan for fresh air circulation on mild days. On moderately warm days, Dodge leaves her home’s main air-conditioning unit off and runs the ductless system — significantly reducing energy usage and cooling expenses. All this for a fraction of the total cost of the dormer project.

A year on, it’s money well spent. “I didn’t want to spend all that money to remodel and skimp on one minor thing,” Dodge said.

Getting to ‘yes’

Dodge’s experience is a common one for Southwest Minneapolis homeowners, said Claire Ferrara, customer experience manager at Standard Heating & Air Conditioning. Many old homes in the area don’t have existing ductwork at all. Even in those with older forced-air heating systems, ducts may barely reach the upper floor — as in Dodge’s case.

Nevertheless, Ferrara said, “the answer to the question, ‘Can I add air conditioning?’ is almost always ‘yes.’” A few years back, Standard installed a custom climate-control system in the 185-year-old Sibley House, Minnesota’s oldest surviving residence.

For homeowners who don’t happen to own a state treasure, the real question is: How much disruption is too much?

“If you want ductwork to serve multiple levels of your home, you have to be willing to take up closet space,” Ferrara said. In a home without enough closet space, a soffit — a duct-hiding drywall bump-out running along the walls or ceiling — may be the only solution.

The only solution involving traditional ductwork, that is. For homeowners not willing to sacrifice floor space in already-cramped older homes, there’s usually a better option: ductless mini-split systems like Dodge’s.

ductless mini-split condenser
The ductless mini-split condenser outside Erika Dodge’s home.

Choices, choices 

Southwest Minneapolis homeowners ready to ditch their window units have two basic options: ductless mini-splits and traditional fan coil systems — what most people think of when they hear “central air conditioning.”

Compared with traditional fan coil systems, ductless mini-splits are minimally invasive and relatively affordable. With exceptions, customers should expect to pay $5,000 and up for a ductless mini-split system, Ferrara said; Standard’s customers typically spend between $6,000 and $13,000, depending on the make, output, head count and system complexity. Ductless mini-splits work best for cooling upper half-stories, additions and remodeled areas, such as over-garage bonus rooms.

Traditional fan coil systems with new ductwork start around $15,000 and run up to $30,000 for the typical Southwest Minneapolis home, Ferrara said. Since these systems run ducts to every room served, their construction very often involves modifying walls or ceilings. An outdoor condenser connects to a basement or attic fan coil unit, which blows cool air through a network of six-inch-diameter ducts. Traditional fan coils are ideal for cooling an entire floor and for “gravity cooling” lower levels — allowing cool air to sink from a ducted second floor down to the ground floor.

In larger, idiosyncratic homes, high-velocity fan coil systems may be cost-effective. High-velocity fan coil units typically live in the attic, so they’re all but infeasible in homes without enough roof clearance (which means most 1.5-story houses in Southwest). Their three- or four-inch ducts and sprinkler-like outlets are less invasive than traditional fan coil systems, and they effectively cool multiple levels. But they’re invariably more expensive than traditional fan coil systems; for many homeowners, the added expense isn’t worth it.

According to Ferrara, Standard rarely installs high-velocity residential systems. Homeowners seeking multi-floor coverage, like Dodge, often combine ductless systems above and traditional fan coils below. Those upgrading from baseboard to forced-air heating may want to spring for a traditional fan coil system at the same time and merge two invasive, costly home-improvement projects into one.

What do you need?

Ask any reputable HVAC professional what type of air-conditioning system you should buy and they’ll ask you to describe your needs and goals.

“It’s all about what you want to accomplish,” said Jim Dudley, the HomeSmart from Xcel Energy sales representative for Southwest Minneapolis.

Investing in a traditional fan coil system makes more sense if you plan to remain in your home for some time, Dudley said. If you’re just looking to cool a smaller portion of your home, or want to be able to turn off your furnace in late March, rather than mid-May, a ductless mini-split makes more sense.

As Dodge learned, ductless systems double as fresh air circulators; they also have dehumidifying properties. Dudley said that makes them ideal for musty quasi-attics and finished basements. In homes with open floor plans and better interior air circulation, their cooling power holds its own against traditional fan coil systems.

Will Tajibnapis cools his entire two-story, circa-1911 Kingfield home with three Mitsubishi ductless heads. The largest unit cools the entire downstairs, spraying cool air from the front wall, through the living room and into the dining room addition — a distance of nearly 40 linear feet, by Tajibnapis’s calculation.

Ductless also speaks to homeowners looking for a “finer touch,” said Mike Moe, another HomeSmart sales rep. In 2016, Moe installed a small Bryant ductless mini-split in the 300-square-foot bonus room above his Nokomis detached garage. A traditional fan coil system would be overkill in such a small space, Moe said, and a window unit without dehumidifying capabilities would make the place feel “cold and clammy.”

Moe also prizes his ductless unit’s near-endless modulation; unlike a traditional fan coil system, there’s no “on-off” binary. “You don’t need full capacity very often in Minnesota,” Moe said. “At 50% capacity, the system is just quietly cooling and dehumidifying.”

Moe’s ductless mini-split is also great for taking the chill off, although performance declines with the outdoor temperature. Below zero, it’s functionally useless.

ductless system’s exterior lines
A gutter-like enclosure conceals a ductless system’s exterior lines. Submitted photos

Checking expectations

Ferrara encourages clients to think about what future homeowners might want, too. Keeping those window units around is still the cheapest option, but these days, that choice comes with a real opportunity cost.

“Air conditioning is more of an expectation today,” said Ferrara. “It’s a ‘need to have,’ not a ‘nice to have.’” Even if your new system doesn’t pay for itself, homes with working, well-maintained air-conditioning systems tend to command a premium over comparable homes without warm-season climate control.

Does that mean you need to snake six-inch ducts through every room of your house, tearing up hardwood floors and raining plaster as you go?

Absolutely not, Ferrara said. She tells overly ambitious homeowners to move past the notion that one must have cooling in every single room of the house.

“You need heating in every room of the house,” she said. “Not cooling.”

This is Minnesota, after all.