The Harvard Center for Green Buildings and Cities (CGBC) will retrofit its headquarters, a pre-1940s house in Cambridge, MA, into an ultra-efficient, healthy, positive energy structure. Targeting the most rigorous efficiency standards ever achieved by a building retrofit, HouseZero has the following performance goals:
1. Almost zero energy required for heating and cooling
2. 100% natural ventilation
3. 100% daylight autonomy
4. Zero carbon emissions, including embodied energy in materials
HouseZero will model a healthy indoor environment with natural light, pleasing acoustics, and zero off gassing materials. Designed to be durable, functional, flexible, comfortable, and connected to its natural environment, the house will promote well-being and worker productivity.
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This demonstration project attempts to address the global environmental challenge of climate change by focusing on inefficient existing buildings, which account for vast amounts of energy use and carbon pollution worldwide. While numerous new buildings have achieved net-zero or positive-energy performance goals, the retrofit potential of the current U.S. building stock has not been thoroughly explored. As such, the CGBC intends to demonstrate that by coupling current technologies with better design, retrofits of our existing building stock can, indeed, achieve rigorous energy efficiency goals. By retrofitting the current residential building stock in the United States to achieve even some of HouseZero’s radical efficiency standards, we can achieve significant energy savings, which will translate into billions of dollars in savings per year.
Some of HouseZero’s upgrades are solely required to transform the house into a functional office for up to 40 researchers and staff, but most enhancements to the existing house are viewed through the lens of the home renovation market. The CGBC believes that the best ideas should be transferable to other homeowners as a recipe for significant energy and carbon use improvements to their existing structures without costly or wasteful teardowns. While a homeowner may not be able to implement every aspect of HouseZero, applying one or more of its components could positively impact its environment, the health of its occupants, and building operating costs.
Rather than approaching the house as a “sealed box,” the building envelope and materials of HouseZero are designed to interact with the seasons and the exterior environment in a more natural way. Much like a layered approach to clothing, the house is meant to adjust itself seasonally, and even daily, to reach thermal comfort targets. We will fully replace the HVAC system using a different paradigm which relies on additions of thermal mass and radiant surfaces throughout the house. A geothermal heat pump will also be installed for peak (extreme) conditions. Natural ventilation will be used to adjust heating and cooling needs throughout the house as required and other materials will help to control fluctuations in humidity by naturally absorbing and releasing moisture in the air. Artificial lighting will not be used during daylight hours because the design of the house is optimized to maximize daylight use and passive solar practices in each space. In other words, whenever daylight is available outside, natural daylight will be provided inside the building. Solar strategies will be employed to protect direct sun during peak summer loading periods, take in the maximum amount of indirect solar (all seasons) and allow direct winter sun to penetrate the interior of the house to a maximum depth. HouseZero uses materials that are all typically low-impact, and recyclable wherever possible with extremely low life-cycle costs.