Woolsey Gardens

The Woolsey Gardens Solar Microgrid system consists of several subsystems that will be monitored and controlled by the microgrid control system. The list provided below illustrates the innovative approaches employed on the project within each of the microgrid subsystems.

▪. Bifacial Solar Panels. The 184.8 kW (DC) rooftop solar canopy system consists of south-facing, 10-degree tilted rows, capable of producing 271,375 kWh of solar energy (presuming 1,467 kWh/kW-DC) in a year.

▪. Battery Energy Storage System (“BESS”). The BESS consists of Lithium Ferro-Phosphate (“LFP”) solution with 512 kWh of energy capacity and 250 kW charge/discharge capacity, along with BESS inverters that have grid-forming, black-start, and dynamic load transfer features.

▪. Microgrid Controller. The Microgrid Controller will be provisioned by Eaton, along with the Load Management solution, including the various levels of smart circuit breakers.

▪. Load Management. The Load Management solution ensures seamless operation with the Microgrid Controller.

▪. Smart Circuit Breakers. The project is currently specifying 72 smart circuit breaker panelboards with hundreds of separately controllable circuit breakers each with integral power and energy metering.

The mechanical system utilizes tested and proven mechanical technology and envelope design while integrating new efficient technology to create a hybrid system that can be replicated for future projects.

Residential heating and cooling loads are mostly determined by envelope gains and façade orientation. Zoning central mechanical systems based on façade orientation enables individual units to function at optimal capacity only when required, thereby minimizing energy wastage. Highly efficient rooftop energy recovery ventilators provide tempered to fully conditioned ventilation air for each residential unit. A highly efficient remote condensing unit provides heating and cooling to the energy recovery ventilator. A terminal unit within each residential unit varies airflow from code minimum to a predetermined maximum so that the internal temperature of each unit never goes above 80°F. Each unit has a localized thermostat to give the occupant control. All air is returned to the rooftop unit for heat recovery. Fan energy is minimized by sizing all ductwork for a low pressure drop. When needed, electric baseboard heaters are used for top-up heating. Additionally, optimizing the envelope with passive house features such as reduced glazing, increased wall insulation, and internal/external shading significantly reduces cooling and heating demand.

All-electric domestic hot water systems with Air-Source Heat Pumps (“ASHPs”) and hot water storage tanks are becoming an industry standard in California. Initially, the team chose a system relying on phase change material; however, because it required significant energy draws during peak hours, the team instead chose the following particular system because it fit well with the ZNE and the “no net energy draws during peak hours” goals set for the building.

▪. CO2 ASHPs. To reduce the global warming potential of the DHW system, the team specified CO2 ASHPs.

▪. Additional Hot Water Storage for Load Shifting. An additional 1,420 gallons of hot water storage is provided, versus traditional ASHP domestic hot water system, for a total of 2,500 gallons., which stores 1,334,400 BTUs of heat stored. This allows for DHW demands from 4pm to 9pm to be met without the ASHPs operating.

▪. Waste Heat Recovery Coils. Four heat recovery coils are provided on the sanitary waste main, which will pre-heat the domestic cold water line feeding the domestic hot water system. This will provide an estimated 975,000 BTUs of heat per day and reduces the overall energy usage of the domestic water heating system by this amount.

Energy Use Intensity (“EUI”), calculated as the amount of energy used per square foot annually, is a metric used to indicate a building’s energy performance. At the onset of the project, the team determined that plug loads, or variable discretionary consumption, will be a critical factor impacting the project’s ability to reach its zero net energy target. For households, the benefit of lower consumption is not only a lower carbon footprint but also lower utility bills. Many programs rely primarily on regularly offered workshops or training sessions to educate residents about the benefits of reduced consumption, and other new and emerging strategies to reduce energy consumption. The Woolsey Gardens program, however, proposes to be more comprehensive and impactful by offering the following:

▪. Regular Workshops.

▪. Hardware Supported by Custom Software. The project team will design software to connect smart circuits to user-friendly, interactive graphics that visualize the relationship between energy consumption and dollars on a real-time and aggregated basis.

▪. Financial + Other Dis/incentives. To dis/incentive residents, the program will implement financial and other rewards/penalties to discourage excessive consumption and support moderated consumption. The initial, and ongoing updates to, program design will be informed by rigorous ongoing analysis.

▪. Robust, Ongoing Econometric Analysis to Fine-Tune Program.

According to the WoodWorks Institute, Woolsey Gardens is on track to be the first Type IV-C building in California. As a pioneer, Woolsey Gardens intents to share its experiences with other affordable housing builders as well as regulatory bodies to facilitate the expansion of this mass timber building type. Constructed in a single phase, the project will consist of eight above-grade stories of Type IV-C Mass Timber construction with one concrete basement level below. Mass timber is essential to the sustainability goals of the project. Mass timber construction not only works well with the carefully designed and efficient mechanical, energy, and plumbing systems but also positively contributes to the project’s whole building and life cycle goals. Most importantly, mass timber enables the critical scalability and replicability goals of NCLT, who seeks to expand the viability of this alternative solution to address climate change and California’s affordable housing crisis.

It is well documented that the embodied carbon profile of mass timber is significantly better than that for concrete or steel. According to SCB’s Whole Building Life Cycle Analysis (WBLCA) models in Tally, there is a 28% reduction in Global Warming Potential for the timber structure compared to the baseline concrete structure. Emerging studies are beginning to demonstrate that mass timber may provide thermal mass to the building. Oak Ridge National Labatory found that “significant impacts of the thermal inertia of the mass timber wall assemblies on the annual energy use—especially on the peak demand as compared to the standard 2x4 and 2x6 lightweight wall systems.”

▪. Bicycle Parking. One secure stalls provided for each. unit.

▪. Building Orientation. The design employed passive house solar shading and natural ventilation strategies to optimize energy efficiency and indoor comfort. The inclusion of shading devices reduces solar heat gain during hot months while maximizing natural daylight, diminishing the need for mechanical cooling systems & fostering a comfortable, well-lit interior environment. Taking the wind analysis done early on, the design incorporates cross ventilation within the units & corridors, empowering residents to naturally cool their spaces before resorting to mechanical systems.

▪ Glazing. The team assessed the window-to-wall ratio (“WWR”) and Solar Heat Gain Coefficient (“SHGC”) of the glazing. By reducing the glazing percentage from 40% to 35%, the project team not only lowered costs due to reduced glass usage but also reduced the embodied carbon footprint and increased the thermal envelope energy performance. The SHGC increase also helped in reducing embodied carbon and meeting EUI targets. Careful consideration was placed on determining the WWR to avoid overly reducing it, as this would impact the building’s aesthetics, both from an interior residential viewpoint and in terms of the building’s exterior design.

▪. Planters & Water. The ground level planter will treat runoff from the paved area within the property line. The second floor planters will treat runoff from the roof level. Proposed plant material will be low water use and/or drought tolerant. Furthermore, all fixtures throughout the building are beyond code minimum low-flow water-saving fixtures, significantly impacting the amount of water to be saved over the lifetime of the building.

▪. Urban Greening. All pavement will have a high solar reflective index. Planting will emphasize a California native palette with wildlife value to attract pollinators and birds. Planted area at the ground level will be maximized taking into account the area required for path of travel and underground utilities. Street trees will be added at all possible locations. Bike racks will be located at the streetscape to encourage bicycle commuting. Community planters are proposed at the second-floor terrace allowing for residents to grow their own food. Site lighting will be Dark Sky compliant.