As the third largest school district in the US, CPS is making smart energy choices to save money and provide healthier, more effective learning environments. By holistically integrating energy and sustainable design improvements into construction and renovation projects, our schools can significantly reduce energy consumption and costs. These savings can then be redirected to educational needs such as additional teachers, instructional materials, or new computers.
The facilities must be flexible, incorporating robust and resilient systems that minimize operational cost, energy usage and carbon emissions. System designs shall minimize maintenance and simplify control strategies. Designs are to consider a combination of both active and passive strategies. An energy simulation model is required to evaluate design options and to document performance relative to the ASHRAE standard referenced in LEED. A separate simulation may be required to demonstrate code compliance.
Passive Strategies
Passive design is a system or structure that directly uses natural energy such as sunlight, wind, temperature differences, or gravity to achieve a result without electricity or fuel (no grid power or fuel is required for operation). Passive strategies are encouraged as they provide non-mechanical and potentially low maintenance methods for reducing energy consumption. Potential strategies include but are not limited to:
- Trombe walls and thermal mass to mitigate temperature swings throughout the day.
- Building massing and orientation to optimize solar exposure.
- Thermal chimneys/natural ventilation to cool and ventilate portions of the building (Note: underground ductwork is not allowed).
- External solar shading to reduce building heat gain, including: architectural shading elements and trees and other plantings to provide seasonal shading of windows from direct sunlight.
- Daylight Harvesting to reduce lighting energy.
- Light shelves and clerestory windows reduce lighting energy and heat gain and minimize roof penetrations.
- Light colored and highly reflective materials.
- Outdoor materials with high solar reflectance to reduce heat gain and indoor reflective surfaces minimize the need for electric lighting.
- Envelope improvements beyond ASHRAE 90.1 minimums, either through thermal efficiency, reduction in window-to-wall ratio, and minimizing infiltration, shall always be the first step in reducing energy usage.
Active Strategies
Active design is a system or structure that uses or produces electricity. Maintenance considerations are of primary concern when evaluating active strategies, with a preference for more standard or lower maintenance options. Potential strategies include, but are not limited to:
- Energy Star and WaterSense labeled equipment, appliances, and fixtures as a minimum performance standard.
- Condensing boilers with variable primary pumping and higher temperature differentials to increase operating efficiency and reduce pumping energy.
- Variable primary chilled water systems with higher temperature differentials to increase operating efficiency and reduce pumping energy.
- Water cooled systems to reduce cooling energy usage.
- CO2 Control in large rooms with high occupancy variance and dedicated AHUs (Air Handling Units) such as gyms, auditoriums, dining rooms, etc.
- De-stratification fans in high ceiling areas to allow higher summer set points and to reduce operating energy.
- Lighting Controls to reduce operating energy and reduce building cooling loads such as smart controls responding to available daylight and occupancy sensing controls. Plug loads control allows to control operating power and reduce amount of phantom power used by the building.
- Renewable Energy - solar power (photo-voltaic, solar thermal (pool heating) and wind to reduce utility energy loads.
- Geo-exchange – heating and or domestic hot water to reduce energy loads. VAV heat pump air-handlers. Individual zone heat pumps are not allowed.