Britta McCarthy’s compact, eco-friendly home in Lexington

In June 2019, Britta McCarthy, newly single, took a 3½-week car trip from Los Angeles, where she had been living for three years, to Lexington, where she would resettle. Along the way, she toured architecturally significant buildings, including Taliesin West, Frank Lloyd Wright’s light-filled winter home and studio in Scottsdale, Arizona, and The Chinati Foundation, Donald Judd’s minimalist museum and installation site in Marfa, Texas.

Six months later, McCarthy closed on a 748-square-foot, architecturally insignificant home in Lexington. Then, that same evening, she headed to Denmark to visit family.

In Denmark, McCarthy soaked in the architecture of Copenhagen, the islands, and the countryside, snapping photos as reference for her redesign. “I’m inspired by the new, small-scale homes being built there, which are highly sustainable and make such efficient use of space,” she says. “I channeled my Danish roots and newly acquired West Coast vibes to create this home.”

McCarthy, a designer herself, was determined to live small and build green. Still, she needed to expand and really wanted a carport. Preexisting, nonconforming setbacks on three sides compelled McCarthy to maintain the home’s footprint and framing. She reinforced the structure, built new, 6-inch-thick walls, and incorporated a variety of insulation methods.

“This is a high-efficiency energy retrofit,” she says. “We went totally fossil-free, used healthy, natural materials, and oriented oversize windows for maximum climate control.” She also saved every scrap of wood, repurposing where possible to minimize what went into the landfill.

To enlarge the home, McCarthy lopped off the gable roof and topped the first floor with a boxy second story, which she rotated 90 degrees so it’s offset from the original structure. The move met setback requirements, added 850 square feet, and allowed for a carport on the east. If she (doubtful) or a future occupant (probable) wanted to expand further, there are three opportunities: finish the newly insulated basement; enclose the carport; or put on a third story.

Before photograph of the house, which had a gabled roof and no carport. — Before the addition: Replacing the gable roof with a second‑story allowed for a generous increase in the first‑floor ceiling height.from Britta Design

The interior layout and window placements make the most of the home’s compact footprint. “I created a lot of alignment in the floor plan so wherever you stand, there are windows with views and sunlight, so spaces never feel tight,” the designer says. “Also, the hallways and stairway are generous; narrowing them makes a house feel small.”

The entryway is also the mudroom, hence the large-format, cement-like porcelain floor tiles — McCarthy bought a whole lot of the discontinued style — and radiant heat. “Consistent floor material helps expand a space,” she says. The dropped maple plywood ceiling infuses warmth, makes the entryway feel more welcoming, and accentuates the higher ceilings beyond it.

The floor tile and wood ceiling carry through the passageway to the main living space, then wrap an unglazed tile-clad wall with a high-efficiency wood-burning fireplace insert. “When I realized it would be crazy not to have a fireplace in New England, I borrowed space from the closet and bath to accommodate it,” McCarthy explains. “It generates enough heat to warm the first-floor bedroom and living area if the power goes out.”

Large expanses of glass grace the main living space. Three tall, fixed windows and a stack of three awning windows face a tangle of trees on the south. Pushing the operable windows to one side allows for ventilation without compromising the height of the other three, which would have interrupted the view. “I was determined to avoid the expense and lead time of custom windows, so all the windows in the house are standard size,” she says.

A wall with a wood stove in a living room. In front of it, there's a chair. To the right, there's a framed TV hanging on the wall. — McCarthy used leftover plywood to frame the wall-hung television next to the wood stove.Joyelle West

An adjacent slider leads to a bluestone patio for dining and lounging. Inside, McCarthy’s collection of 1960s J.L. Møller chairs surrounds a white oak table by Ethnicraft, and oak plywood pendants by Graypants emanate warmth above it. “The Scandinavians, especially the Danes, are so good at designing lighting,” she says. “They understand how to make homes feel cozy.”

A sectional from American Leather — McCarthy gives it high marks on value and workmanship — anchors the seating area, hugging a reclaimed oak and metal coffee table from New England maker Jeff Soderbergh. A maple and leather lounge chair that her parents purchased in the 1960s in Denmark is a well-patinated treasure. “Every time I sell a home, potential buyers ask to buy it, but I plan to pass it down to my kids,” she says.

The Fireclay Tile backsplash — note the pulled-apart horizontal spacing that is both a fun pattern and a sizing strategy employed to avoid cutting the tiles — is the focal point on the opposite wall. A Baltic birch plywood box is as much minimalist Donald Judd-esque art as storage. Like the island base, it was made by Ryan Messier, a woodworker whom McCarthy met in a North Bennet Street School woodworking class. As for appliances, this was McCarthy’s first foray into induction cooking. “A client told me to walk the talk, so I did and have since convinced other clients to do the same,” she says.

In addition to the bedroom and full bath on the first floor, there are two bedrooms and two baths on the second. The hall bath sports pretty, patterned floor tile — the very first item McCarthy picked for the house — and a soaking tub. “Americans don’t typically associate this style tile with a Scandi aesthetic, but it truly speaks to what Scandinavian design is: warm, eclectic, and happy,” she says.

The bathroom window is centered on the bathroom door, which, in turn, is aligned with the door to the primary bedroom, allowing light to penetrate the entire span of the second floor. Both bedrooms have walls of south-facing windows, too. McCarthy loves how light spills in and how her bed floats over the backyard. “I call this home my treehouse,” she says. “It’s my happy place.”