With the United States representing a diverse land area, many have wondered if zero energy schools are truly possible across all climate zones. A recent National Renewable Energy Laboratory (NREL) study sponsored by the Building Technologies Office has found that using today’s advanced technologies, optimal design for energy consumption, and strong and climate-appropriate energy consumption targets, it is possible.
Pathways for managing energy consumption include optimal design of the building envelope fenestration, lighting systems, heating ventilation and air conditioning (HVAC) systems, controls and service water heating. The study provides specific energy use per square foot (EUI) targets to cost-effectively achieve zero energy and provides systems integration strategies to balance energy consumption and energy supply so that schools will meet their own energy needs.
Extensive energy modeling was used to determine the effectiveness of all pathways to zero energy considered within the study. Prototypes representing typical K-12 schools segmented by primary and secondary school types were developed through energy modeling tools. An iterative process allowed for the adjustment of variables:
- Climate zones and subzones
- Geometry of space types
- Envelope properties
- Fenestration
- Infiltration
- Interior lighting
- Daylighting
- Exterior lighting
- Plug and process loads
- HVAC
- Service flow enhancements
- Refrigeration
- Workflow enhancements
Each of these variables was adjusted based on its ability to meet building specifications, e.g. ASHRAE 90.1-2013, climate zone requirements, and ultimately create parameters that can achieve zero energy. The study has culminated in suggested pathways for project teams that address energy-efficiency measure values, types of efficiency levels necessary to reach specific EUI target, plug and process load strategies.
While this feasibility study presents several ways to achieve zero energy, the researchers acknowledge the existence and importance of innovative techniques project teams are also creating. Zero energy is an end product that can be reached through a variety of pathways; this study is intended to support the process.
Recently, SF Unified School District (SFUSD), a Zero Energy Schools Accelerator partner, incorporated the EUI target established by the study in districtwide design and construction. “SFUSD mandates that all new construction meet an EUI of 20 kBtu / square feet / year,” according to Nik Kaestner, director of sustainability for SF Unified School District. “Additionally, modernization projects are encouraged to reach the same target over the course of two bond cycles.”
Zero energy design can help school districts meet their energy cost saving, STEM education, and resilience goals. BTO is working to develop technical and diagnostic analysis of associated pathways to ensure that stakeholders are equipped with solutions to meet their goals.