City College of San Francisco - Child Development Center
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Green Building Design
Gross Size of Project:
- Thermal Comfort Strategy
The units at CCSF strongly support thermal comfort, enhancing occupant productivity and satisfaction. The number of operable windows for ventilation exceeds minimum requirements. The efficiency/quality of thermal comfort with the Raised Floor System is superior to overhead or wall mounted, fan diffused systems in most modular units. Air is supplied by multiple floor diffusers, creating an upward flow of fresh air via natural convection and exhausted through ceiling return outlets, unlike overhead systems that mix cool and heated air near the ceiling, spending energy forcing it down to user zones. Cool air is supplied at higher temps/lower velocity than overhead systems, reducing discomfort from high air speed/cold spots. Energy savings are due to diffusers’ close proximity to occupants and user-defined location, direction, and flow; the living roof that supports consistent indoor temperatures; R-19 rigid expanded polystyrene (EPS) in the roof and the floor; and R-15 EPS in the walls.
- Indoor Air Quality Strategy
The CCSF classrooms exemplify FROG’s effort to circumvent the health problems, low test scores and high absentee rates posed by indoor air pollution. We use Low/No VOC carpet tiles, ceiling tiles and interior paint. Sealants meet/exceed the requirements of the Bay Area Air Quality Management District Regulation 8, Rule 51. Intersept antimicrobial preservative in the carpet tiles combats a broad spectrum of bacteria/fungi. BioBlock inhibits the spread of mold/mildew on ceiling tiles. Under floor air distribution delivers outside air from below directly to the occupants’ breathing zone. New air replaces contaminated air instead of diluting it with old air, the method of most portables. FROG units allow for up to 100% outside air, providing clean air to the occupants, reducing any remaining VOCs/bacteria in occupied areas. Unlike most portables’ fiberglass batt insulation, FROG’s Ultratouch cotton fiber insulation resists microbial growth; doesn’t cause skin irritation; formaldehyde-free.
- Daylighting Strategy
The FROG building’s integrated system of customizable window wall units, sunshades and clerestory windows allow the interiors of the CCSF classrooms to be illuminated far more naturally and efficiently than any other modular classroom. The customizable window wall system (85% of the exterior walls) consists of interchangeable window/wall panels of user-specified colors /materials. Each 2’x4’ panel can be high performance glass or insulated composite panel. Design customization allows a perfect balance between the need for abundant light in some areas (i.e. play/learning rooms) and less in others (i.e. nap areas), shadow reduction and/or heat gain. Sunshades are mounted to the south and west side of the curtain walls to protect each classroom from an excess of direct sunlight and reduce glare. A signature feature of FROG’s structure is the unique clerestory. Each unit’s sloped roof assembly is enveloped on three sides by clerestory windows that flood the unit with natural light.
- Acoustic Strategy
The acoustical ceiling panels used at CCSF contain a 70% Noise Reduction Coefficient (NRC). This reduces most echoing within the building, thus increasing speech clarity. In addition to the R-19 roof insulation (with space for an additional R-19), the living roof reduces outside noise transmission. The under floor air distribution system implements a pressurized plenum and harnesses natural convection to assist the airflow out of the floor diffusers and directly into the occupied zone, eliminating the noisy ducts of traditional portable models carrying air being pushed at high velocities. Most modular classrooms use a wall-mounted HVAC system, resulting in high levels of noise. Project FROG eliminates this excess noise with its Powerpak, which places the HVAC system in an exterior room separated from the learning area by an auxiliary room or restroom and an extra thick wall filled with sound-attenuating insulation.
- Energy Efficiency Strategy
The FROG units at CCSF use high quality recycled/recyclable materials, including recyclable acoustic ceiling tiles (75% recycled content (RC)); raised floor tiles (33.9% RC:1.8% post consumer (PC)/22.1% post industrial(PI)); Ultratouch batt insulation (85% PI recycled natural fibers). Carpet tiles (44% RC) and vinyl tiles (92% RC, 25% PC) can be replaced individually (instead of the entire floor) and reused. Most modular buildings consist of wood; all FROG units are steel (up to 100% RC) which can always be recycled. Non-steel materials (ie wood) are field cut, creating excess waste; FROG parts are cut in a metal shop and all excess is recycled. The FROG units are designed for minimal site disruption. Each unit’s foundation takes up less than 1/2 of the overall sq. footage of the unit itself, requiring only 7.5 cu yards concrete. The living roof reduces rainwater runoff; serves as a protective layer, increasing the building’s lifespan; and contributes to water/air purification.
- Architectural Excellence
Customized and flexible, the new campus at CCSF is architecturally stylish inside and out. Exciting and expanding upward, the undulating roofline rises in the middle and lowers at the sides to provide a dramatic expression. The grand curved rear (which hides unsightly mechanical equipment) is trimmed with rounded edges to set a modern tone. The customized exterior earth tone colors were chosen to blend with the surrounding neighborhood context. The window wall system has interesting patterns of wall vs. window to create a unique exterior and functional interior. To foster creativity and encourage collaboration, the interior is full of natural light with optimal acoustics and clear sight lines. The careful configuration and positioning of the units creates a comfortable and safe campus environment, and is truly beautiful from every angle.
- Economic Practicality
By using FROG units, CCSF realized significant economic savings that will multiply over time. Due to grouping/orientation, the CCSF FROG units are more than 30% more energy efficient than Title 24 requires. FROGS are built quickly enabling buyers to save on construction escalation costs (up to 12% per year). Since FROG units are California DSA Pre-Certified buildings and can be approved “over-the-counter”, the permit fees are lower than traditional construction. FROG installation costs are lower than traditional construction since units can be installed on a variety of surfaces with minimal waste, site preparation, clean-up, and landscaping. FROG buildings will perform optimally and inline with permanent structures. Costs associated with removal, demolition, and temporary building replacements are eliminated. The use of steel and glass eliminates roof/wall/flooring degradation for low long term costs. FROG modular building requires less on-site skilled labor.
Energy Efficiency: FROG succeeded in making CCSF the most energy efficient of its kind. The raised floor system delivers air via floor diffusers directly to the occupied zone, creating an upward flow of fresh air of natural convection. By using higher-temperature air for cooling, the system can utilize outside air for a longer period, thereby reducing HVAC energy consumption. The natural light from the clerestory/window walls decrease the artificial light necessary for internal illumination. The glass is Solarban70XL Solar Control Low-E and blocks 63% of the direct solar heat, reducing the energy and costs of cooling, while still having the benefits of natural light. The smart lighting system balances the amount of natural light with Daylight Sensors, allowing for less energy usage and lowers wasted energy with Occupancy Sensors. Photovoltaic panels produce energy onsite for the units use and distribute back to the city grid when not in use.