When Bobby Johnston and Ruth Mandl found the townhouse they wanted to buy in Bedford-Stuyvesant, Brooklyn, it had just one glaringly obvious problem: It was too nice.
“We were originally looking for something that was pretty dilapidated,” Ms. Mandl said. “And this one looked a lot more pristine than we thought we wanted.”
Mr. Johnston, 39, and Ms. Mandl, 36, are married architects who run the firm CO Adaptive, and they were keen to do a gut renovation that reflected their ideas on design and sustainability, while also making space for children.
On a professional level, “we wanted the opportunity to renovate something of our own,” Ms. Mandl said, noting that they previously lived in a one-bedroom apartment in nearby Bushwick. On a personal level, she added, “we were thinking of starting a family and wanted more space and access to a backyard.”
The handsome 1889 townhouse they found on a charming tree-lined block was not what they envisioned. It had been beautifully preserved over the years and still had its original intricate woodwork and plaster molding intact.
“You could tell that somebody had loved it through its entire life, and taken good care of it,” Ms. Mandl said.
The townhouse was also a single-family home, and they were hoping for a two-family house that could generate income and help them secure a larger mortgage. But after deals on two other houses fell through, they were getting impatient, so they went to see it anyway.
“We completely fell in love with the block, the house and the yard,” Ms. Mandl said. “And we were the only people at the open house.”
Bottom: Emily Gilbert for The New York Times
They moved quickly and struck a creative deal to buy it: They would pay $1.4 million, but only if they were allowed to complete a targeted, temporary renovation to convert the house into a two-family home before the closing.
“We filed with the city to get a Letter of No Objection for it to be a two-family,” Mr. Johnston said. “And we did a quick $4,000 renovation to add a second kitchen and a dividing wall between two units, so we were able to leverage a mortgage for a two-family.”
They closed in July 2016 after selling their Bushwick apartment, which had roughly doubled in value over the previous five years, and split the profit between the new purchase and anticipated renovation costs. Then they got to work.
As proponents of sustainable building, they wanted to design their home according to passive house standards that would radically reduce the building’s energy consumption. And as practitioners of modern architecture, they wanted to make it lighter and brighter, and introduce simple, clean-lined details.
Finding themselves with a bonanza of late 19th-century architectural details, however, they decided to split the difference and blend the new with the old. When demolition began in March 2017, Mr. Johnston and Ms. Mandl instructed their contractor, LB General Contracting, to gingerly pry out and preserve every significant piece of woodwork while stripping the interior down to the studs.
They erected a tent in the backyard to store the material they planned to reinstall and donated the rest to the architectural salvage store Big Reuse. Hoping to keep a few of the plaster elements, but unable to move them for construction, they left a decorative archway and an ornate ceiling medallion in place on the parlor level and crossed their fingers. The archway survived, but vibrations from the construction work eventually sent the medallion crashing to the floor.
With the townhouse cleared out and opened up, they began adding the elements necessary to make it a super-insulated, airtight passive house, an incredibly energy-efficient type of building that is beginning to catch on with homeowners and developers.
Heating and cooling a passive house uses “a fraction of the energy you need for a regular building — like, one-tenth,” said Andreas M. Benzing, the president of New York Passive House, a nonprofit organization.
Bottom: Emily Gilbert for The New York Times
Where passive house projects were relatively rare just a few years ago, there are now 169 across New York State, either completed or in the works, Mr. Benzing said. They include private homes as well as large-scale developments like Sendero Verde, an affordable housing project spanning a full city block in East Harlem, with a target completion date of 2022, that aspires to be one of the largest passive house projects in the world.
To convert their 19th-century townhouse, Mr. Johnston and Ms. Mandl expanded the depth of the front wall by about a foot to add extensive new insulation. They installed triple-glazed tilt-and-turn windows with gaskets. They sealed walls and ceilings with an Intello air barrier. They installed motorized exterior blinds that, unlike curtains, can block sunlight before it enters the house on hot summer days.
With such measures in place, they no longer needed a conventional furnace, so they capped the gas line at the street. An energy-recovery ventilator provides fresh, filtered air from outside, while capturing and recycling heat from exhausted indoor air, and a small electric split heating-and-cooling system provides a boost, when needed.
Those electric components are powered by a photovoltaic system on the roof, which also provides more than enough power for the home’s appliances and lights, as well as an electric-car charging station in the front yard. Once a week or so, they run a cable across the sidewalk to the street, to charge their BMW i3.
“Even with charging the car fully at home, we’re still net positive,” Mr. Johnston said, explaining that they generate more electricity than they use and feed the surplus back to the grid.
While reducing — or reversing — their energy consumption was a priority, Ms. Mandl said, she initially became interested in building a passive house after experiencing the comfort of her parents’ passive house in Vienna. The feeling inside is one of “amazing luxury,” she said, thanks to the fresh air and consistent temperature. “There’s just no temperature jump. You can sit by the window during a blizzard and not feel any draft.”
Another benefit of an airtight house is that it is incredibly quiet. Street noise stays on the street, Mr. Johnston said. “It’s completely soundproof.”
Mr. Johnston and Ms. Mandl also decided to soundproof the rooms inside their home after attending dinner parties at friends’ houses where “everybody has to whisper while the kids are asleep,” Mr. Johnston said.
Ms. Mandl had given birth to their daughter, Lucia, now 2, just weeks before they started construction, and they didn’t want to have to worry about noise once they moved in. They installed acoustic mats beneath floors, a double layer of drywall with sound-deadening Green Glue on the walls, and interior doors with gaskets and drop seals.
“We can have dinner parties downstairs when she’s asleep upstairs,” Ms. Mandl said, “and she would never even know that there’s loud music.”
The primary residence occupies about 1,400 square feet on the top two floors. On the parlor level, the couple installed a large, modern kitchen with Reform cabinet doors over Ikea carcasses in a space that was previously a back parlor, as well as a powder room and laundry area with frosted-glass doors and walls.
Upstairs, they carved out three bedrooms, including a master suite with an en suite bathroom, and a second bathroom split between a toilet room and a shower room, which Ms. Mandl said is typical in her native Austria.
They reinstalled and painted the original woodwork they had saved in the backyard tent, and had an artisan add new plaster crown molding in the living room that is similar to what was there before. After introducing thicker walls and new windows, the original window trim was no longer compatible, so Mr. Johnston and Ms. Mandl decided to play up the difference by giving the openings a simple plywood edge, a detail that they also used for interior doorways. In the kitchen, they designed a custom plywood pegboard wall with adjustable shelves.
On the garden level, they created a 700-square-foot, two-bedroom apartment with similar details. The downstairs unit was completed first, so Mr. Johnston and Ms. Mandl moved into it with their daughter in April 2018, as work continued upstairs. The rest of the project was completed five months later, at a total cost of $720,000, and the family moved upstairs.
Now, they rent out the downstairs apartment on Airbnb when not using it to entertain family and friends. Their hope is that opening their home to visitors will introduce others to the advantages of a passive house.
“I feel that you have to experience it in order to fully appreciate it,” Ms. Mandl said. “We leave a flyer for them, so even if they’ve never heard of it, they get to read about what it is.”
