Philadelphia’s Onion Flats is constructing low-cost buildings that use design, mechanical equipment and residents’ behaviour to slash fossil fuel consumption.
4 min
The shiny, onyx-coloured building appears alien in its drab, postindustrial Philadelphia neighbourhood—the love child of a “D-volt battery and the Death Star,” as one local architecture critic put it, admiringly.
Called Front Flats, the four-story building is wrapped on all sides and roof by 492 translucent, double-sided solar panels. The building is airtight and extraordinarily energy-efficient, its developers say.
By driving down consumption and producing electricity from its solar panels, Front Flats is designed to generate its own power. But this isn’t a corporate headquarters where executives can spend lavishly on a showcase edifice. It is 28 apartments, built on a budget for renters who make below the area’s median income. One-bedroom apartments rent for under $1,400, less than the $1,750 average for the neighbourhood, according to rental-listings website Zumper.
Onion Flats, the Philadelphia-based architecture-and-building firm behind Front Flats, is at the forefront of designing low-cost buildings that use design, mechanical equipment and residents’ behaviour to slash fossil fuel consumption.
“As an architect, if I’m not designing buildings that contribute no carbon to the environment then I’m being totally irresponsible,” says Tim McDonald, 56, a principal in Onion Flats. “I might as well be designing buildings that sit on marshmallows.”
Buildings contribute 38% of global greenhouse-gas emissions, including heating, cooling and construction materials, according to the International Energy Agency. The building industry is growing more interested in low-carbon construction, but few architects or contractors have experience with it. Many believe it significantly raises costs. Onion Flats wants to demonstrate that it can be done affordably and at scale, prodding others to follow and policymakers to enact energy-efficient building codes.
Mark Lyles, a project manager at the New Buildings Institute, a nonprofit based in Portland, Ore., that promotes low-carbon construction, says the work by Onion Flats is noteworthy because it ties together on-site renewable energy generation with “deep efficiency.”
Mr McDonald and his partners, he says, are “always asking where can I reduce energy consumption. A lot of his projects are bellwethers for where things are going.”
Onion Flats is one of several firms trying to build very energy-efficient housing. In Manhattan’s East Harlem neighbourhood, a 709-unit affordable housing development called Sendero Verde is under construction; it is intended to be among the most energy-efficient multifamily buildings in the world. In Portland, Ore., a 10-story, 127-apartment retirement community is slated to start construction this spring, and is expected to use up to 60% less energy than a typical multiunit building.
Onion Flats is a family affair. Two of Mr McDonald’s brothers, Patrick and Johnny, are also principals, as is Howard Steinberg, a friend since seventh grade in suburban Philadelphia.
Front Flats is its most ambitious attempt at a “net zero” building—a structure that throughout a year generates as much energy as it consumes. The solar skin—which is 60cm away from the windows and exterior—generates electricity, keeps the building cool in the summer by blocking the sun, and provides privacy to tenants. “You can’t see into people’s apartments, but they can see you,” Mr McDonald says.
The building, which opened in January 2020, doesn’t have a natural gas line and uses electricity for heat and hot water. From January through June, it generated more electricity than it needed and sold the excess onto the local power grid, Mr McDonald says. In July, August and September, it drew more kilowatt-hours than it generated. Overall, it is still ahead, Mr McDonald says, but since the pandemic slowed leasing and the building wasn’t fully occupied until the fall, the true test of whether the building is net zero will come this year with apartments full of people charging their mobile phones and playing on game consoles.
The firm has built several residential buildings in Philadelphia over the years and plans to keep going. The principals have learned that actual energy consumption is often greater than what the models predict. The culprit is “plug load”; people plug in bigger televisions and more electricity gobbling devices than expected.
About a mile south of Front Flats, Onion Flats built another apartment building called the Battery which attempts to tackle this problem. LEDs on the outside of the Battery are connected to particular apartments, although which light connects to which isn’t obvious to passersby or residents. When an apartment is using less electricity than its share of what is being generated, it glows green; otherwise, it glows red. The system, after encountering a software problem, is expected to go online this year.
After building its first government-subsidized, ultra energy-efficient townhouse for low-income residents in 2012, Onion Flats lobbied the Pennsylvania Housing Finance Authority, a state agency that distributes federal low-income tax credits, to consider an energy efficiency standard known as “passive house” construction when determining which builders were awarded the coveted credits. “We said ‘If we can do this, why can’t other developers’?” says Mr McDonald. After one meeting, the state agreed to give developers extra consideration for using a passive house design, beginning in 2015. (Onion Flats didn’t use the credit for Front Flats.)
The passive house projects didn’t cost much more to build than traditional apartment buildings—despite costing considerably less to heat and cool, according to an analysis of construction costs for residential projects over the past five years that the authority performed at the request of The Wall Street Journal.
“Not only is that encouraging, but the end result should be lower utility costs for the life of these passive house apartment buildings,” Robin Wiessmann, executive director of the agency, said in a statement. Tenants at Front Flats pay US$40 a month for utilities. Fifteen states are copying Pennsylvania’s approach and have begun using incentives to encourage more super-efficient apartment buildings.
Mr McDonald says he hopes that buildings that generate their own electricity will become commonplace.
“People don’t say, ‘I want to be known as an architect that has bathrooms in all our buildings.’ No, that’s just a given,” he says. “Being green, being sustainable, being carbon-neutral, should just be what it means to be a good architect.”
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What a quarter-million dollars gets you in the western capital.
Alexandre de Betak and his wife are focusing on their most personal project yet.
Ahead of the Games, a breakdown of the city’s most desirable places to live
7 min
PARIS —Paris has long been a byword for luxurious living. The traditional components of the upscale home, from parquet floors to elaborate mouldings, have their origins here. Yet settling down in just the right address in this low-rise, high-density city may be the greatest luxury of all.
Tradition reigns supreme in Paris real estate, where certain conditions seem set in stone—the western half of the city, on either side of the Seine, has long been more expensive than the east. But in the fashion world’s capital, parts of the housing market are also subject to shifting fads. In the trendy, hilly northeast, a roving cool factor can send prices in this year’s hip neighbourhood rising, while last year’s might seem like a sudden bargain.
This week, with the opening of the Olympic Games and the eyes of the world turned toward Paris, The Wall Street Journal looks at the most expensive and desirable areas in the City of Light.
Known for historic architecture, elegant apartment houses and bohemian street cred, the 6th Arrondissement is Paris’s answer to Manhattan’s West Village. Like its New York counterpart, the 6th’s starving-artist days are long behind it. But the charm that first wooed notable residents like Gertrude Stein and Jean-Paul Sartre is still largely intact, attracting high-minded tourists and deep-pocketed homeowners who can afford its once-edgy, now serene atmosphere.
Le Breton George V Notaires, a Paris notary with an international clientele, says the 6th consistently holds the title of most expensive arrondissement among Paris’s 20 administrative districts, and 2023 was no exception. Last year, average home prices reached $1,428 a square foot—almost 30% higher than the Paris average of $1,100 a square foot.
According to Meilleurs Agents, the Paris real estate appraisal company, the 6th is also home to three of the city’s five most expensive streets. Rue de Furstemberg, a secluded loop between Boulevard Saint-Germain and the Seine, comes in on top, with average prices of $2,454 a square foot as of March 2024.
For more than two decades, Kyle Branum, a 51-year-old attorney, and Kimberly Branum, a 60-year-old retired CEO, have been regular visitors to Paris, opting for apartment rentals and ultimately an ownership interest in an apartment in the city’s 7th Arrondissement, a sedate Left Bank district known for its discreet atmosphere and plutocratic residents.
“The 7th was the only place we stayed,” says Kimberly, “but we spent most of our time in the 6th.”
In 2022, inspired by the strength of the dollar, the Branums decided to fulfil a longstanding dream of buying in Paris. Working with Paris Property Group, they opted for a 1,465-square-foot, three-bedroom in a building dating to the 17th century on a side street in the 6th Arrondissement. They paid $2.7 million for the unit and then spent just over $1 million on the renovation, working with Franco-American visual artist Monte Laster, who also does interiors.
The couple, who live in Santa Barbara, Calif., plan to spend about three months a year in Paris, hosting children and grandchildren, and cooking after forays to local food markets. Their new kitchen, which includes a French stove from luxury appliance brand Lacanche, is Kimberly’s favourite room, she says.
Another American, investor Ashley Maddox, 49, is also considering relocating.
In 2012, the longtime Paris resident bought a dingy, overstuffed 1,765-square-foot apartment in the 6th and started from scratch. She paid $2.5 million and undertook a gut renovation and building improvements for about $800,000. A centrepiece of the home now is the one-time salon, which was turned into an open-plan kitchen and dining area where Maddox and her three children tend to hang out, American-style. Just outside her door are some of the city’s best-known bakeries and cheesemongers, and she is a short walk from the Jardin du Luxembourg, the Left Bank’s premier green space.
“A lot of the majesty of the city is accessible from here,” she says. “It’s so central, it’s bananas.” Now that two of her children are going away to school, she has listed the four-bedroom apartment with Varenne for $5 million.
Garrow Kedigian is moving up in the world of Parisian real estate by heading south of the Seine.
During the pandemic, the Canada-born, New York-based interior designer reassessed his life, he says, and decided “I’m not going to wait any longer to have a pied-à-terre in Paris.”
He originally selected a 1,130-square-foot one-bedroom in the trendy 9th Arrondissement, an up-and-coming Right Bank district just below Montmartre. But he soon realised it was too small for his extended stays, not to mention hosting guests from out of town.
After paying about $1.6 million in 2022 and then investing about $55,000 in new decor, he put the unit up for sale in early 2024 and went house-shopping a second time. He ended up in the Invalides quarter of the 7th Arrondissement in the shadow of one Paris’s signature monuments, the golden-domed Hôtel des Invalides, which dates to the 17th century and is fronted by a grand esplanade.
His new neighbourhood vies for Paris’s most expensive with the Notre-Dame quarter in the 4th Arrondissement, centred on a few islands in the Seine behind its namesake cathedral. According to Le Breton, home prices in the Notre-Dame neighbourhood were $1,818 a square foot in 2023, followed by $1,568 a square foot in Invalides.
After breaking even on his Right Bank one-bedroom, Kedigian paid $2.4 million for his new 1,450-square-foot two-bedroom in a late 19th-century building. It has southern exposures, rounded living-room windows and “gorgeous floors,” he says. Kedigian, who bought the new flat through Junot Fine Properties/Knight Frank, plans to spend up to $435,000 on a renovation that will involve restoring the original 12-foot ceiling height in many of the rooms, as well as rescuing the ceilings’ elaborate stucco detailing. He expects to finish in 2025.
Over in the Notre-Dame neighbourhood, Belles demeures de France/Christie’s recently sold a 2,370-square-foot, four-bedroom home for close to the asking price of about $8.6 million, or about $3,630 a square foot. Listing agent Marie-Hélène Lundgreen says this places the unit near the very top of Paris luxury real estate, where prime homes typically sell between $2,530 and $4,040 a square foot.
The Boulevard Périphérique, the 22-mile ring road that surrounds Paris and its 20 arrondissements, was once a line in the sand for Parisians, who regarded the French capital’s numerous suburbs as something to drive through on their way to and from vacation. The past few decades have seen waves of gentrification beyond the city’s borders, upgrading humble or industrial districts to the north and east into prime residential areas. And it has turned Neuilly-sur-Seine, just northwest of the city, into a luxury compound of first resort.
In 2023, Neuilly’s average home price of $1,092 a square foot made the leafy, stately community Paris’s most expensive suburb.
Longtime residents, Alain and Michèle Bigio, decided this year is the right time to list their 7,730-square-foot, four-bedroom townhouse on a gated Neuilly street.
The couple, now in their mid 70s, completed the home in 1990, two years after they purchased a small parcel of garden from the owners next door for an undisclosed amount. Having relocated from a white-marble château outside Paris, the couple echoed their previous home by using white- and cream-coloured stone in the new four-story build. The Bigios, who will relocate just back over the border in the 16th Arrondissement, have listed the property with Emile Garcin Propriétés for $14.7 million.
The couple raised two adult children here and undertook upgrades in their empty-nester years—most recently, an indoor pool in the basement and a new elevator.
The cool, pale interiors give way to dark and sardonic images in the former staff’s quarters in the basement where Alain works on his hobby—surreal and satirical paintings, whose risqué content means that his wife prefers they stay downstairs. “I’m not a painter,” he says. “But I paint.”
French interior designer Julie Hamon is theatre royalty. Her grandfather was playwright Jean Anouilh, a giant of 20th-century French literature, and her sister is actress Gwendoline Hamon. The 52-year-old, who divides her time between Paris and the U.K., still remembers when the city’s 9th Arrondissement, where she and her husband bought their 1,885-square-foot duplex in 2017, was a place to have fun rather than put down roots. Now, the 9th is the place to do both.
The 9th, a largely 19th-century district, is Paris at its most urban. But what it lacks in parks and other green spaces, it makes up with nightlife and a bustling street life. Among Paris’s gentrifying districts, which have been transformed since 2000 from near-slums to the brink of luxury, the 9th has emerged as the clear winner. According to Le Breton, average 2023 home prices here were $1,062 a square foot, while its nearest competitors for the cool crown, the 10th and the 11th, have yet to break $1,011 a square foot.
A co-principal in the Bobo Design Studio, Hamon—whose gut renovation includes a dramatic skylight, a home cinema and air conditioning—still seems surprised at how far her arrondissement has come. “The 9th used to be well known for all the theatres, nightclubs and strip clubs,” she says. “But it was never a place where you wanted to live—now it’s the place to be.”
With their youngest child about to go to college, she and her husband, 52-year-old entrepreneur Guillaume Clignet, decided to list their Paris home for $3.45 million and live in London full-time. Propriétés Parisiennes/Sotheby’s is handling the listing, which has just gone into contract after about six months on the market.
The 9th’s music venues were a draw for 44-year-old American musician and piano dealer, Ronen Segev, who divides his time between Miami and a 1,725-square-foot, two-bedroom in the lower reaches of the arrondissement. Aided by Paris Property Group, Segev purchased the apartment at auction during the pandemic, sight unseen, for $1.69 million. He spent $270,000 on a renovation, knocking down a wall to make a larger salon suitable for home concerts.
During the Olympics, Segev is renting out the space for about $22,850 a week to attendees of the Games. Otherwise, he prefers longer-term sublets to visiting musicians for $32,700 a month.
Hidden in the hilly expanses of the 18th Arrondissement lies a legendary street that, for those in the know, is the city’s most exclusive address. Avenue Junot, a bucolic tree-lined lane, is a fairy-tale version of the city, separate from the gritty bustle that surrounds it.
Homes here rarely come up for sale, and, when they do, they tend to be off-market, or sold before they can be listed. Martine Kuperfis—whose Paris-based Junot Group real-estate company is named for the street—says the most expensive units here are penthouses with views over the whole of the city.
In 2021, her agency sold a 3,230-square-foot triplex apartment, with a 1,400-square-foot terrace, for $8.5 million. At about $2,630 a square foot, that is three times the current average price in the whole of the 18th.
Among its current Junot listings is a 1930s 1,220-square-foot townhouse on the avenue’s cobblestone extension, with an asking price of $2.8 million.
