Borrego Springs Library

Zero Energy Certified under the International Living Future Institute (ILFI) and the County of San Diego’s third Zero Net Energy (ZNE) library, the Borrego Springs Library features energy-efficient design, solar shading, daylight harvesting, a durable building envelope, and onsite renewables to achieve ZNE performance in the harsh Anza Borrego desert climate. The County partnered with Stok from the outset to determine the building’s ZNE feasibility, then to ensure the building was designed and operated at ZNE.

At a Glance

Client:County of San Diego

Location:Borrego Springs, CA

Industry:Government

Size:13,165 SF

Project Team:RNT Architects (Architect)BN Builders (General Contractor)

Certifications:Zero Energy (ILFI)LEED (Gold)

Solutions:

Zero Net Energy (ZNE) Feasibility Analysis
Zero Net Energy (ZNE) Modeling
Measurement & Verification (M&V)

The Challenge

The County of San Diego engaged Stok to accurately model energy consumption for this architecturally unique library in an uncertain and unforgiving climate to ensure the building met the County’s sustainability goals: LEED Gold certification, ILFI Zero Energy Certification, and alignment with the County’s net zero portfolio plan. Specifically, Stok:

Conducted a pre-RFP ZNE feasibility study to identify anticipated annual consumption and evaluate potential for the project to achieve ZNE with a buffer
Performed energy modeling for ZNE in parallel with the design team's code compliant and LEED models
Acted as the County's advocate to ensure the project remained on track for ZNE throughout design and construction
Set up measurement and verification to track ongoing energy performance of the building

Susan Freed

Project Manager, Energy & Sustainability Division at County of San Diego

“Designing an important community facility with unpredictable usage in a harsh desert ecosystem to achieve Zero Net Energy operations was a highly technical challenge and involved close alignment and cooperation between all project team members. The process relied on Stok’s deep energy expertise, years of experience with modeling ZNE and working with the County on our ZNE program, and doggedness to keep the project team focused and engaged along the ZNE journey. The fact that we were able to achieve our ZNE target with this unique and beautiful high-performing jewel is a testament to that guidance that forged successful teamwork. Our ongoing partnership with Stok has been fundamental to the County’s continued ZNE achievements across our portfolio, and Borrego Springs Library is a high point.”

Zero Energy Certified under the International Living Future Institute (ILFI) and the County of San Diego’s third Zero Net Energy (ZNE) library, the Borrego Springs Library features energy-efficient design, solar shading, daylight harvesting, a durable building envelope, and onsite renewables to achieve ZNE performance in the harsh Anza Borrego desert climate.

The Solution

ENERGY MODELING FOR RESILIENCY

The library is designated as a cool zone for local residents, which means it may be open outside of normal operating hours during periods of high temperatures, making it more difficult to model predicted energy use. Stok worked with the County of San Diego Library Team to identify historical cool zone events and included estimates for increase in future events due to climate change. This information was then included in the energy model to more accurately predict the energy consumption of the building above and beyond a standard code-compliant facility.

ON-SITE RENEWABLES

The County includes a 10% buffer on photovoltaic (PV) system sizes on ZNE buildings to account for future operational changes and increasing temperatures, but the uncertainty of number and duration of cool zone events involved significant coordination and predictive estimating. Stok’s ZNE model was used to predict annual energy consumption, which in turn was used to size the PV system, giving the County confidence that the building could operate as ZNE for the foreseeable future.

ONGOING TRACKING OF PERFORMANCE IN OPERATIONS

Stok developed an end-use submetering strategy and worked closely with the design team to specify, install, and program the submeters that are integrated into the County’s central Building Automation System (BAS). The submeters track ongoing energy performance, enabling the team to ensure the building continues to perform at ZNE in operations.

For its achievements in energy efficiency and ZNE design, the Borrego Springs Library was honored with the 2019 AIA San Diego Energy Efficiency and Integration Award. Learn more about this ZNE verified community space in this New Buildings Institute case study.