Xilinx Case Study
Accelerating Replicable ZNE Retrofits Through High Performance Facade Optimization
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The transformation of a dark and inhumane 1970s tilt-up concrete office building into a high performance, light-filled modern workplace was enabled by a thoughtful retrofit of the existing envelope. By sculpting the existing building skin into a healthy, high performing filter of light, heat, and air, the resultant building aims for net zero energy cost and also achieved substantial carbon savings through reuse of the existing, high-footprint building.
Adding new daylight apertures, carefully crafted shading elements, and a new thermal enclosure of rigid mineral wool insulation around the existing concrete walls offered the primary tools for design transformation. When executed together, this design enabled low energy mechanical solutions and ultimately an estimated EUI that is fully offset by rooftop and building-integrated photovoltaics.
The existing concrete walls were insulated to isolate the thermal mass from the exterior and reduced both the heating and cooling energy by 50% over the existing building energy use. Additionally, light wells were punched through strategic locations to maximize daylight distribution, which paired with new LED lighting, properly specified high performance glazing, and finely tuned external shades made of BIPV panels that control direct sun and balance daylight levels, reduced the lighting energy use by some 80%.
A local utility incentive program is validating the modeled results through a yearlong study, comparing submetered building energy use to modeled end use predictions. The program offers controls assistance and optimization during the first year of occupancy to meet anticipated performance goals. While initially seen as individual efficiency measures, the design team discovered the interdependent relationships between seemingly disparate energy saving design measures and optimized the cascading set of decisions that enabled this design transformation.
In the United States, nearly half of all commercial buildings were constructed prior to 1980 (CBECS, 2017). Construction of these buildings predated rigorous updates to state and national building codes
The transformation of this building was catalyzed by well-tuned modifications to the building skin. An integrated design team advised on optimization strategies related to opaque wall thermal performance, daylight apertures
Historic energy bills revealed baseline energy use. A detailed site energy audit augmented this data, which documented plug loads, equipment types, equipment efficiency, existing HVAC systems, existing lighting systems and
The individual design measures to retrofit this building were relatively modest in isolation. But when used together, small, good design decisions cascaded to the next, enabling radically better performance. Daylighting
Conclusion and Future Work
This project highlights the potential mistake of considering design as a list of efficiency measures. Particularly when focused on the building skin, high performance buildings are possible when the interdependencies
Thanks to the project design team: Noll and Tam – Architecture, Integral Group – MEP, KPFF – Structural, BFS – Landscape, Charles M Salter Assoc. – A/V and Telecom. Most importantly to our colleagues at Integral Group, this project was successful due to the skilled contributions of Laura Fedoruk, Emily Jacobson, Willy Stober, Shannon Allison, John Andary, and Dylan Connelly.
Rights and Permissions
CBECS. “A Look at the U.S. Commercial Building Stock: Results from EIA's 2012 Commercial Buildings Energy Consumption Survey.” https://www.eia.gov/consumption/commercial/reports/2012/buildstock/. Accessed September 20, 2017.
Sullens, et al; The Total Carbon Study, November 13, 2015.