Is This Harvard Prototype the Greenest House in America?

Harvard’s HouseZero. Photo: Michael Grimm

Like a lot of revolutionary command centers — Trotsky’s Mexico City retreat, for instance, or Bill Gates’s Los Altos garage — the two-story house at 20 Sumner Road in Cambridge, Massachusetts, looks a little out of date from the outside. It’s a handsome but unassuming place, built nearly a century ago and freshly shingled in blond wood, with a soon-to-be-weathered front porch and a New England dormer on the roof. A wheelchair ramp zigzags up a landscaped slope to the front door, one of the few signs of contemporary values noticeable from the street. Solar panels line the roof and a protruding metal frame shades each window like the visor on a baseball cap, but you might hardly notice those features as you hurry toward Harvard Yard, a few blocks away.

Nobody lives in Harvard’s HouseZero, unless you count the Ph.D. students who may spend the occasional night at their workstations. This office/lab/walk-in-computer/showcase houses the university’s Center for Green Buildings and Cities, and it would be hard to think of a more apt headquarters for a more urgent mission. Amid all the engineering whiz-bang designed to battle climate change, this wood-frame body freckled with sensors and veined with five miles of cable stands out for its self-evident simplicity and radical potential. Most other environmentally sensitive buildings rely on advanced machinery: hyperefficient air conditioners, motion-activated window shades, and so on. HouseZero dispenses with contraptions that refrigerate the house in summer or blast heat in winter. Maintaining a comfortable indoor temperature depends on an ingredient that most architecture forcibly exclude: fresh air.

On the day I meet the center’s director, Ali Malkawi, the temperature in what must have once been the house’s front parlor, now opened up into a warm, bright lounge, is a good 50 degrees higher than it is outside, the indoor air feels soft and serene, and our conversation is pillowed in quiet. Malkawi hired Snøhetta and the engineering firm Skanska to design the renovation, but in truth he is bored by its beauty. The cottony light and spa-like finishes, the perforated honeycomb enfolding the stairs, even the glass-walled pod tucked up under the eaves — all these are sops to those who judge his headquarters by what it looks like and how it behaves, rather than what it can teach. “Looking at it as a piece of architecture diminishes the building. It’s really an instrument for us to do research,” Malkawi says.

Before moving into the center, Malkawi convinced Harvard to pay to take the place apart and rebuild it with off-the-shelf components, including a geothermal heat pump to take the edge off heat waves and polar vortices. Thicker-than-typical concrete floors absorb and radiate heat, and there’s an extra layer of insulation in the walls. But the real innovation lies in the software, which continuously regulates windows and vents to keep air flowing through the building and achieve ever-finer gradations of comfort. Graduate students keep refining the algorithm, sifting through the 16 million data points that the house’s sensors collect each day and gauging how cloud cover, air temperature, and the foliage on the trees in the yard interact with the staff’s clothing, how closely their warm bodies cluster in each room, and how much carbon dioxide the houseplants vacuum up. Everyone knows that warm air rises, but here, sensors in a chimney can study the nuances of real-time convection flows to see exactly what happens when a flue is nudged or a door swings open three rooms away. The house can respond immediately or over time: A computer calculates how much warmth the concrete floor slab has stored during daylight hours, how much will be released overnight, and how quickly to blow that heat away or trap it inside, depending on the next day’s forecast.

“Understanding building behavior is one goal to the research; the other is to figure out how can we command buildings,” Malkawi says. “The idea is to allow the building to use data, learn, and adjust.”

Homebuilders have known for millennia how to use wind, sunshine, stone, and earth to stay comfortable indoors. Romans directed temperate breezes through a portico and into a courtyard. Greek peasants used whitewash to repel the midday heat. Adobe husbanded the cool of the night. But extreme weather and urban living defeats these ancient techniques, and the future promises much, much more of both. And so modern living has meant sealing ourselves into airtight boxes and fouling the air outside in order to make the indoors invariably temperate. It sounds effortless — it’s hot, so turn on the air conditioner; it’s cold, so turn up the heat — but the machinery of creating millions of indoor environments has become as vast as costly and potentially lethal as war. Europe and United States devote about 40 percent of the energy they consume to heating and cooling buildings — far more than the amount eaten up by transportation.

That number has dropped over the last couple of decades, as mechanical systems have gotten gradually more efficient, especially in new construction. Passive House protocols rely on super insulation, tight joinery, and triple-glazed windows to prevent air from leaking in and out. Still, there is a limit to how virtuous an air-conditioning apparatus can ever be, since even the most advanced machines get old and wheezy and have to be replaced, a process that sucks up even more energy.

Inside the house. Photo: Michael Grimm

“It’s easy to control the thermal environment with zero energy” in temperate areas, Malkawi says. “But people don’t do it! We have like hundreds of millions of buildings, and they don’t even try. It’s amazing. It’s like a crime.”

That’s not quite fair. Some architects have adapted ancient techniques of natural ventilation to desert houses and office buildings, and while some projects have proven their effectiveness over time — Foster and Partners’ pioneering 1997 Commerzbank in Frankfurt remains one of the world’s largest sustainable towers — these one-offs have yet to transform common practice.

HouseZero achieves a standard that few architects and developers hold themselves to, offsetting the energy used to manufacture, transport, and install the materials for its construction. It’s not the first or the only project to whittle down a building’s energy use to almost nothing, or even to pump extra power into the grid. In 2012, the firm Baumschlager Eberle Architekten opened 2226, a new office building in Lustenau, Austria, with no mechanical heating or cooling. Two years later, Snøhetta renovated a 30-year-old office building in the Norwegian city of Sandvika into Powerhouse Kjørbo, which pumps out more energy than it uses and shares the bounty with its neighbors. But years later, these projects remain tantalizing examples of what the world might look like if it suddenly all turned into Northern Europe.

There’s a powerful steampunk appeal to an approach that targets a building’s operating system first and leaves its physical heft more or less alone. To describe HouseZero as a renovation is a half-truth; it might have been cheaper and easier to start from scratch than to strip the structure down to its studs and rebuild it out to Malkawi’s specifications. Even so, the result, a basic body with a high-tech brain, intimates a future in which every tract house, tenement, and landmark could receive a range of possible upgrades, from a radical overhaul to a natural ventilation kit comprised of cables, sensors, and window actuators. Sustainability can’t remain just a pricey feature of second homes and Class A office towers. “It’s important to develop refurbishment strategies that are very efficient but at the same time maintain the architectural character of the building,” says Marius Nygaard, a professor of sustainable design at the Oslo School of Architecture and Design. “It’s about rediscovering the knowledge embedded in traditional architecture and redefining it for the present.”

The Green New Deal calls for buildings all over the country to drastically cut energy consumption, a goal that a group of cities, including New York and Los Angeles, had already pledged to achieve. The most unsustainable way to hit those environmental benchmarks would be a multitrillion-dollar drive to install new lighting and HVAC systems, and reproduce an improved version of the current bell-jar approach to city living. Fortunately, the lessons that emerge from HouseZero could yield software cheap and flexible enough to work in modest houses and gargantuan towers, controlling that technical marvel, a window that opens and shuts. Maybe the future of the great indoors will feel like the past.

A few weeks after my visit, a brutal cold snap whipped in from the Midwest, bringing wind chills in the Boston Area down to minus-20 degrees. Afterwards, I emailed Malkawi to see how theory had fared in the face of real-life extremes. He answered tersely: “Was very comfortable.”

Is This Harvard Prototype the Greenest Building in America?