Harvard University’s on-campus council for all things green building is creating the most energy-efficient retrofit attempted so far. The Harvard Center for Green Buildings and Cities (CGBC) is collaborating with Snøhetta to convert its headquarters, a 1924 stick-built house in Cambridge, into HouseZero, a sustainable system that is expected to set a precedent for the future of green reconstruction around the world.
Image via Snøhetta
The center’s current home, a three-story building clad in cedar paneling, was purchased by the Graduate School of Design in 2011. The retrofit aims to showcase a level of efficiency usually achieved only in new construction. “We want to demonstrate what’s possible,” said Ali Malkawi, professor of technology and founder of the CGBC. “[We want to] show how this can be replicated almost anywhere and solve one of the world’s biggest energy problems: inefficient existing buildings.”
HouseZero will require almost zero energy for heating and cooling, include 100-percent-natural ventilation and daylight autonomy as well as achieve zero carbon emissions — even in the embodied energy of its materials. It will be the epitome of a healthy indoor environment where students and researchers will tackle questions related to the long-term benefits of building greener architecture and greener cities.
The project is predicated on the building’s future ability, once fully retrofitted, to predict and adapt to changing weather patterns and generate new levels of proficiency. Though it may seem like a simple concept — the greening of an existing structure — what makes this particular project so challenging is the use of multiple advanced sustainable technologies combined to predict the maximum energy-efficiency of a single building.
Image via Snøhetta
More than a passive house with an overtly insulated envelope, HouseZero will be defined by its ability to push the limits of sustainable design using the best green systems under the sun. It will include a glazed solar vent or chimney that will harness thermal updraft, moving air from the basement to higher levels of the building. Next to the house, a parking lot will be transformed into a rain garden using excavated soil. This will reduce landfill and aid in rainwater retention while an elevated green roof will mitigate storm-water runoff and diminish solar gain in the space below.
The building will feature massive windows covered in sculptured shrouds that will shade and cool the interior from direct sun in the summer months and allow the sun to generously heat the spaces during winter months. Interior ventilation will be controlled by a window actuation system — smart technology that will automatically open and close windows to maintain a comfortable indoor environment.
The building’s roof and walls will be further insulated with a focus on creating an airtight waterproof space that increases efficiency. Photovoltaic shingles on the roof will power the house and be stored in a battery for use on cloudy days. Extra energy will go back into the city’s power grid. The project will also feature an underfloor radiant system and geothermal heat pump adopted from Nordic technology. Additional solar thermal panels on the roof will supply hot water inside the house.
Image via Snøhetta/Plompmozes
The interior itself will be designed in an open plan with glass partitions and exposed wooden beams. The space features a palette of locally sourced natural clay and birchwood along with new flooring made of a concrete mixed with sustainable slag cement. A new staircase will also be added to the interior and feature faceted wall paneling meant to decrease circulation noise.
Not only will HouseZero include all of these radical changes, it will entirely switch typologies from a small residential piece of architecture to an institutional construction, meaning it must be compliant with a new set of energy codes.
To hit never-before-seen energy targets in one structure, the CBGC and Snøhetta conducted five months of workshops and computational simulations testing out the building physics, thermal responses, CFD analytics and solar gain as well as daylight and acoustical properties.
Image via Snøhetta/Plompmozes
“We’re trying to see what we can push in terms of efficiency ratings,” said Malkawi, “because houses can be beyond just caulking and changing the windows. We’re developing algorithms to figure out problems in existing buildings that core retrofits, when done correctly, can solve naturally.”
Snøhetta’s senior architect Kristian Edwards echoed Malkawi’s idea. “What’s most interesting about HouseZero is how much can be done with relatively little,” he said. “At least in terms of retrofit, a reductive rather than additive approach means that the combination of both the overview and the eyes of the architect or designer remain imperative to a successful outcome.”
The design team sees HouseZero as the recipe that existing homes and other structures need to achieve major energy- and carbon-use improvements. Even implementing one or more components of the project’s rigorous and radical standards would positively impact building operating costs, the health of its occupants and the impact on the environment.
Once HouseZero is complete — it is now under construction and expected to take seven to eight months — the CGBC hopes to construct a similar project in a different country, this time centered on a new local context and climate.