The atmosphere feels curiously different inside the remodeled Craftsman house in Northwest Washington, D.C., where Vanessa Bertelli and Stefano Negri live with their three children. The heavy humidity outdoors is replaced with a rush of clear, fresh air. The city noise evaporates into silence once the door is closed. In every room, from the basement to the attic, the temperature remains surprisingly consistent. The building, decorated in a Scandinavian minimalist style, has white, uncluttered walls and exposed wooden ceilings and looks like any well-designed home with fine modern touches. But this is no ordinary house.
For the past two years, Bertelli and Negri have worked to retrofit this nearly century-old house to bring it to “net-zero energy” status — meaning an environmentally sustainable dwelling that produces at least as much energy as it uses. Motivated by scientific consensus that the Earth’s temperature is reaching record-high levels because of climate change caused by human activity, the family has designed their home to drastically reduce their energy use. And they employ on-site solar energy production to offset what they do consume.
“I have three children. This is personal to me. I need to make sure that by our everyday actions we are not making this worse than it already is,” Bertelli says of the climate crisis. “It’s not a dream of having a net-zero home. It’s a need.”
American homes devour energy, and most don’t produce any in return. Residential buildings account for more than 20 percent of the nation’s energy consumption, releasing an average of 8.7 tons of carbon dioxide per household every year — around 70 percent more than the average passenger car — according to data compiled by the U.S. Department of Energy. Temperature control, combined with appliances that heat water, chill our food and wash our clothes, account for a majority of that consumption. Meanwhile, the poorly insulated walls and thinly glazed windows that come standard in many American homes allow much of the controlled air to escape, requiring even more energy.
Bertelli and Negri have reinforced their walls and ceilings with thick insulation, sealed the house with an airtight layer, replaced appliances powered by fossil fuels with ones that run on electricity, and installed solar panels.
Yes, these measures reduce your carbon footprint, but they also yield a better quality of life, advocates say. “We can improve comfort and health at the same time that we are lowering operating expenses and improving our environmental impact,” says James Ball, co-coordinator of the National Capital Region chapter of the Net Zero Energy Coalition. “Health and comfort are bigger motivators because they’re personal.”
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It’s typical — and sometimes exhausting — to hear environmental activists rattle off a list of pleasures people should give up to save the planet. Proposals for lowering carbon footprints often demand that people make lifestyle changes to reduce the effects of climate change, whether it’s eating less meat, bearing fewer children or even giving up keeping dogs as pets. Let’s face it: Americans do not always react positively to this messaging. But net-zero homes have the potential to flip that script. They don’t require giving up the joys of modern life; they increase them. The air is filtered and cleaner, the long-term heating and cooling costs are lower, and the comfort level inside is easier to maintain. Americans have only recently caught on to the idea that their homes could be more comfortable using these practices.
In February 2020, after a year of searching unsuccessfully for a net-zero home to buy in the District, Bertelli and Negri turned from 16th Street NW down a quiet side street lined with historical houses. The neighborhood culminated at the entrance to the city’s verdant Rock Creek Park. Along the park’s border stood a brick Craftsman almost hiding beneath the curtain of trees at the end of a stone path.
The old house, uninhabited since the previous owner died more than two years earlier, was desperate for a makeover. Thick mold grew over peeling walls. The roof leaked. Decades of soot caked the stone fireplace in the living room. The attic floor was covered with personal papers, and rooms were scattered with porcelain knickknacks and shoes. Sagging furniture filled the space. A damp unfinished basement housed the home’s primary energy source: a gas-powered furnace connected to rows of ducts lined with asbestos. Rooms contained dehumidifiers or small electrical air-purifier machines, evidence of attempts to maintain air quality.
Bertelli and Negri had toured dozens of homes in the city, but most had been freshly flipped and furnished with new appliances. They passed on all of them. While most net-zero projects involve new construction, Bertelli and Negri wanted to find a house they could refurbish. Building from scratch “felt like a cop-out,” Bertelli says, because of the resources required to construct it. “You’re still not dealing with this issue of our existing residential stock that’s going to have to find its way to net-zero over the next 20 years.”
But working with an existing structure brought extra challenges. “It’s pretty straightforward how to build new energy-efficient buildings,” says Catherine Fowlkes, who co-owns Fowlkes Studio with her husband, VW Fowlkes, and consulted on the architectural designs of Bertelli and Negri’s house. “But renovations are a whole different animal.”
Unlike new builds, which can be oriented to maximize the benefits of the patterns of the sun for energy retention, existing homes may face an undesirable direction. Renovators are stuck working within the form, shape and siding of the buildings. And masonry structures pose a challenge in terms of the physics of adapting passive building techniques — a set of construction concepts that lowers a home’s carbon footprint — to the stone.
There’s also the mystery of what lies beneath. “A lot of times you don’t know what the building is made of until you start opening it up. You can have all the best plans in the world, but you have to be ready to adapt to the actual condition when you open up a wall and realize that it’s crumbling or needs to be significantly improved,” says Ed May, a passive house specialist with the consulting company Bldgtyp.
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But for those looking to retrofit an existing structure, old homes can be more suitable for net-zero overhauls than those built in the past 50 years, says Lindsay Baker, CEO of the International Living Future Institute, which vets and certifies net-zero buildings. “Old buildings are the best,” Baker says. “Buildings from 100 years ago were built before modern air conditioning and lighting. They were built to be naturally ventilated, naturally cooled and naturally lit. It is great for people to invest in those older buildings because they have the bones for it.”
The techniques behind passive construction have been known and applied since the days of skyrocketing energy prices in the 1970s, but American homeowners have been slow to adopt them. Energy costs have been lower in the United States, generally, than elsewhere. That, combined with a divisive political debate over climate change, has kept the U.S. residential home sector from embracing the technology on a widespread level.
“We are almost inconceivably far behind,” May says, emphasizing the benefits in comfort and health that new building techniques provide.
The principles that drive passive home construction and retrofitting are simpler than you might think. They require thorough insulation, closing thermal bridges that allow air to escape, high-quality windows and doors, and a robust ventilation system to control temperature. “It’s really the basic tool kit on all buildings,” May says. Once the house is as efficient as possible, the addition of renewable energy to offset what the home uses makes it “net-zero.”
Bertelli and Negri closed on the house purchase in April 2020, just as the covid-19 pandemic took hold across the country. The organization where Bertelli worked closed down. Unemployed, she threw herself full time into retrofitting the house. She studied online architecture forums that discussed the process, but she was dismayed at how little information was available for those not versed in construction jargon. “They discussed things in words that I didn’t know,” she says. She found a few blog posts, but they mostly focused on new construction instead of retrofits. When she contacted architects and contractors, they advised her that her dream would not be possible. “We couldn’t find anyone. Every person we spoke to said, ‘No, you cannot retrofit a 100-year-old Craftsman to net-zero,’ ” she says. “It was outside the scope of their imagination.”
Bertelli’s frustration is common. “There just aren’t enough general contractors out there specializing in this yet,” says Nicole Tysvaer, CEO and co-founder of Symbi Homes, which builds sustainable housing in the Washington area. “We have the technology. What we’re lacking is the human resources to market, educate and install this new tech. That’s the thing we struggle with every day.”
Over time, Bertelli and Negri found people with expertise who were willing to help. The Brooklyn-based firm 475 High Performance Building Supply provided advice and products, and connected Bertelli with May, who helped guide them through the steps over video conference calls.
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Before they could add anything new, they had to remove all appliances that ran on fossil fuels. They ripped out the gas furnace in the basement, the old water heater and the clothes dryer. The 50-year-old gas cooking range went next, replaced with an induction stove.
Switching everything to electric is a crucial step. “It’s really simple. If you are burning fossil fuels in your home, you have machinery that will never be able to be converted to electricity, which can be sourced by renewable sources” such as solar energy, Bertelli says.
Although grids are currently powered through a variety of energy sources — including nonrenewable coal — many are shifting toward renewables over time. D.C., for instance, has set a target of running the city’s grid on 100 percent renewable energy by 2032.
In 2019, Mayor Muriel Bowser signed a bill mandating a list of energy-reduction goals, establishing the nation’s capital as an aggressive leader in advancing clean-energy construction. The law requires new commercial buildings to meet high-efficiency standards. It promotes net-zero retrofit projects and accelerated solar programs. In July, D.C. became the second East Coast city — after New York — to ban the installation of fossil fuel heating systems in new commercial buildings. New construction projects are required to be net-zero. As part of its Solar for All program, the city provides no-cost solar panel installation to income-qualified residents, including new roofing technology made of solar shingles. All of this is part of the city’s goal to reach carbon neutrality by 2050 and cut its greenhouse gas emissions in half by 2032.
“D.C. is the shining star right now,” says Mark Kresowik, who manages policy for the carbon-free buildings program at RMI, an energy-focused think tank. “That’s probably the best example around the country.”
The city offers financial assistance to people who are retrofitting their homes. Bertelli and Negri were eligible for up to $10,000 in incentives to make the improvements through the Net-Zero Energy Program, which also assisted with permits.
Bertelli’s full-fledged “deep” net-zero retrofit — doing it all at once — is not feasible for every homeowner. While the local government’s financial incentives help, they pay for only a small part of the retrofit. The family spent about $35,000 on replacing windows; two Minotair heat pumps cost $6,000 each, and they bought a Mitsubishi backup for $5,000. Replacing the range and water heater and installing solar panels were additional costs.
But you don’t have to do everything at once. Most people work energy-efficient designs into home renovations gradually to spread out the cost. “We all have to look at transitioning to net-zero energy within our own finances and what we can accomplish in each of our homes,” says Ball, who is slowly bringing his house in Maryland toward net-zero by replacing fossil fuel appliances when they wear out. “As long as we’re using this as part of our decision-making process and aligning toward this outcome, we will find those ways to cost-effectively do it.”
At the same time that governments are supporting environmentally friendly building practices, Bertelli and Negri faced a roadblock from the federal government. Because their house borders Rock Creek Park, Bertelli had to submit plans for exterior changes to the U.S. Commission of Fine Arts, which has the authority to reject building or alteration proposals based on appearance and effect on public land. The commission works to maintain the aesthetic integrity of buildings adjacent to certain federal land in the District, including the National Mall, the White House, Pennsylvania Avenue and several parks. “The environmental agenda and the historical agenda were in conflict,” says VW Fowlkes, a consulting architect on the Bertelli-Negri project.
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The commission pushed back against their request to install solar panels on the roof that would be visible from street level, Bertelli says — an important component to achieving their net-zero goals — and limited them to a small space above the house’s slanted dormers that couldn’t be seen from below. That allowed for only 15 panels, not nearly enough to power the house. To make up for it, she is planning to install more panels on a detached garage nearby, which the commission approved.
Installing new windows set the stage for another issue with the commission. Sealed, multipaned, high-performance windows are essential to maintaining a low-energy building, but the style of these newer models often conflicts with traditional aesthetic preferences.
About 30 to 40 percent of heating energy is lost through windows, says Craig Maierhofer, vice president of business development at Alpen High Performance Products, which manufactures windows that meet passive house standards.
No matter how thick your windows — which typically make up one-fifth of a structure’s facade — are, they will never hold in as much energy as insulated walls. Mitigating energy loss is best achieved with higher performing windows, in which the glass is tightly gasketed together and sealed. The U-Factor of a typical window — the standard measurement of its insulation value — is around 0.30. Bertelli’s triple-glazed high-efficiency windows, by contrast, have a U-Factor of just 0.14 to 0.17, an improvement of nearly 50 percent.
“It’s very important for everyone to be flexible on this so you can hit as many values successfully as possible,” says commission spokesman Thomas Luebke, who adds that the commission would consider future applicants for solar panels, especially as the use of the technology grows. “I think this is probably a pretty good example where everybody got what they were looking for in the end. You have a very high-performance house, and the character of the neighborhood and context was honored. There was no undue impact on the park.”
In the end, the family was able to secure permits for much of the project’s exterior work.
Meanwhile, Bertelli continued work inside, gutting and sealing the house. Passive home builders add several inches of insulation, as well as an extra layer of material to ensure airtightness and vapor control. She added a product called Intello Plus to create a membrane that stretched along the perimeter of the house, wrapping it beneath the drywall from the basement to the roof. “Once your home is airtight, that is the magic,” Bertelli says. “Then you control which air comes in from where, and you can more easily heat it or cool it.”
Buildings can measure energy efficiency by calculating what is called air changes per hour, which is how often all of the air inside the home escapes to the outside, mostly through leaky windows, crevices, roofs, doors, joists or poorly insulated ducts. A typical house of that size and vintage has 15 to 20 air changes per hour. “You are consuming an enormous amount of energy to heat air that gets dispersed to the outside, and you don’t have any control over where it comes from and where it goes,” she says. “Cold air comes in during the winter; the air you’ve heated seeps out to the outside. It’s just incredibly inefficient.”
After installing the airtight seal around the house, adding new windows and insulation, and closing off any other exposure to the outside, it tested at only 0.6 air changes per hour. Fresh outdoor air is brought in and filtered using the heat pumps, which also extract stale indoor air. “I promise you, you want that air to come out of my teenagers’ bathrooms,” Bertelli says.
She replaced the furnace and air conditioning system with two electric heat pumps, which fit in a small closet. Heat pumps pull in hot air from outside and disperse it in the house through ducts. When a home needs cooling, the heat pumps pull hot air from indoors and pump it outside. Heat pumps use about half the electricity that a traditional furnace consumes, according to the Energy Department, but only 14 percent of American homes use them for heating. In June, President Biden invoked the Defense Production Act to speed the manufacture of heat pumps. The Inflation Reduction Act, passed last month, provides rebates and credits for buying them, as well as other financial incentives toward green energy purchases that can reduce a home’s carbon footprint.
The family moved into the house in May 2021 and continued to work on it. Having laid the groundwork, Bertelli and Negri are eager to find out how close they’ve come to achieving net-zero. Once the systems have been in place for a calendar year, they will calculate their electricity use and compare it with what they’ve generated from their solar panels. If needed, they’ll add more panels.
Despite the steep learning curve, Bertelli was surprised by how simple the process was once she understood the basic principles behind greening her house. Not every family has the time, money and tenacity for a massive project like this, but she hopes that as awareness and financial incentives grow, Americans will be able to enjoy the benefits for their own lives.