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Newly-published research shows Harvard’s experimental lab HouseZero achieves high energy efficiency with natural ventilation and thermally active building system

CAMBRIDGE, Mass., February 17, 2022 – The Harvard Center for Green Buildings and Cities (CGBC), in its latest peer-reviewed paper in Energy and Buildings, demonstrates that Harvard’s HouseZero, which serves as both a laboratory and as the CGBC headquarters, can achieve high energy efficiency with combined natural ventilation and a thermally active building system.

The article presents the first comprehensive assessment of the operational performance of the coupled natural ventilation (NV) and thermally active building system (TABS) using one-year high-fidelity measured data of the novel experimental small office building and living laboratory (HouseZero). The research supports the effectiveness and success of the integrated system configurations and control strategies implemented in HouseZero. Specifically, the data demonstrates that the NV and TABS integration and control can effectively control the indoor thermal environment while achieving high energy efficiency. This is also reflected by the low annual energy consumption for heating and cooling described in the paper.

Photos above: (a) TABS piping, (b) geothermal heat pump, (c) automatically operable window and (d) PV panels.

Although the building was operated in a pandemic mode (unoccupied) during its first year of measured operational performance, the data reported in the paper provides pertinent information regarding its initial year’s performance and helps identify the gaps between the design intents and actual operation to form a strategy to fine-tune the systems.

Additional takeaways from the research for future design, retrofit and operation strategies for similar buildings include:

  • High-fidelity building performance monitoring and assessment help identify issues and improve operation management. Interventions proposed include control strategies such as window controls in the summer and operation strategies such as the setpoint for night cooling.
  • A robust design strategy that considers the uncertainties between the design assumptions and the actual operational conditions is recommended; design decisions, such as the size of the heat pump and geothermal systems, can have an impact on operation if uncertainties are not considered.
  • Communication among designers, consultants, engineers, building owners and operators is crucial for the building to achieve design intents; better communication among stakeholders helps identify problems so that they can be solved in a timely manner.
  • A validated simulation model that accounts for building and system characteristics, as well as actual operational conditions, is suggested to support optimal operation. This model can have many uses, including simulating scenarios to determine optimal operation strategies, and providing a reference energy target for real-time monitoring and assessing operational performance, and automated fault detection and diagnostics.

In addition, several strategies to further improve operational performance are also summarized in the paper. In addition to the first published paper about HouseZero, “Zero-carbon balance: The case of HouseZero,” the full peer-reviewed paper “Comprehensive Assessment of Operational Performance of Coupled Natural Ventilation and Thermally Active Building System via an Extensive Sensor Network” can be read here.


Co-Authors of the paper “Comprehensive Assessment of Operational Performance of Coupled Natural Ventilation and Thermally Active Building System via an Extensive Sensor Network” are Bin Yan, Xu Han, Ali Malkawi, Tor Helge Dokka, Pete Howard, Jacob Knowles, Tine Helgi, and Kristian Edwards.