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20 Sumner Road, Cambridge, Massachusetts

Touring the construction site of HouseZero, an experimental sustainable retrofit project and the future home of the Harvard Center for Green Buildings and Cities (CGBC), I was struck by the incongruence between the project’s lofty goals and the entirely ordinary appearance of the building during demolition. This is a typical early-20th-century wood-framed house: rough-sawn lumber with striped plaster stains on the studs, brick fire blocking, diagonal corner braces, and a central chimney buried within the walls.

Working with Snøhetta, the CGBC is retrofitting this unassuming building with a web of data-collecting sensors and actuators, high-mass concrete floors, ground-source heat pumps, a solar chimney, and other features. According to extensive energy modeling, HouseZero — with its photovoltaic shingled roof — will be energy positive and will achieve zero carbon during its 60-year life cycle, offsetting the embodied energy of its materials and construction.

These are laudable goals, particularly for a renovation project conducted almost entirely within the shell of an existing building. Yet Ali Malkawi, founding director of the center, talks about net-zero carbon as if it were merely a side effect. The real goal of the project is to harness computational intelligence to revitalize, recombine, and intensify the impact of known passive heating and cooling strategies. Heat will be transferred in precise quantities, stored in the mass of the building, and released as needed. Sensors will be able to measure wind, temperature, and solar gain, and produce real-time dynamic energy models that will inform automated systems. Weather data combined with predictive algorithms will tune the building to anticipate future conditions.

If successful, our understanding of the capacity of passive may well be transformed by this modestly scaled building and its active computations. This is not a superinsulated sealed box, but a building that breathes with yogic discipline.

HouseZero diagram. Image: Courtesy Snøhetta