Stanford GSB 100% SD Mechanical Narrative 8/17/07Stanford GSB 8/03/07 100% SD Mechanical Narrative Page 2 of 15 Description of Mechanical Systems o Key Concepts The mechanical systems are intended to consume the lowest possible energy, while assuring comfortable, safe and maintainable service for the future. The following key concepts organized within five sections characterize the approach to systems design: 1. Reduced Load: • Improved Glazing: The glazing will be high performance thermally broken double pane insulated units that are spectrally selective and contain a low-emissivity layer. Total glazing will be optimized to assure the best ratio of light transmission to heat transmission. • Improved Opaque Envelope: Roof and wall systems will transmit at least 50% less heat than in a code compliant building via a doubling of the code required insulating capacity. This will be partly achieved through limited thermal bridging along stud lines broken by wrapped insulation. • Reduced Equipment Energy Density: The building energy density in Watts/sq. ft. due to equipment will be reduced through a focused effort on the part of occupants and a performance criteria based purchasing standard for energy consuming equipment (minimum top quartile of market available performance). Additional allowance will be made to provide for future flexibility. • Reduced Lighting Energy Density: The building installed energy density in Watts/sq. ft. due to lighting will be reduced by 25- 40% through optimized installed power density and foot candle requirements. Daylighted spaces combined with daylight dimming systems will further reduce lighting load through the use of a “continuous/off” dimming system. 2. Passive System Application • Natural Ventilation: Natural ventilation will be a sole source or supplemental source of conditioning and ventilation where possible. Operable windows will be incorporated in all perimeter spaces as feasible, Operable louvers in the internal walls will assist in cross ventilation. • External Shading Elements: The external building shades will passively control solar insolation falling on the building facades. The building façade will incorporate external shading elements that will respond to the different orientations to reduce the heat gain (overhangs for south orientation and fins for east/west). • Internal Light Shelves: Internal light shelves will passively aid the penetration of daylight deeper into the occupied space. • Transition Zones: Transition zones (e.g. arcade, lobby, corridor) will allow design temperatures to be at an elevated level at or near the building exterior and gradually lesson until entering the final permanently occupied zone (e.g. offices, classrooms, & conference rooms).Stanford GSB 8/03/07 100% SD Mechanical Narrative Page 3 of 15 • Activated thermal mass: Thermal mass will be used as a passive cooling device by exposing concrete mass slabs in a horizontal configuration (e.g. floors) where possible, thereby allowing passive radiant cooling. The building will be night flushed using cool night air to precool the building and relieve load on the building’s mechanical systems during the day. 3. Efficient and Flexible Active System Application • Displacement Air: Where possible and appropriate, the occupied areas of the building are conditioned by a displacement air system configured for low velocity 68F air supply. Basis of design assumes displacement air in select spaces as highlighted in the system diagrams. • Low Pressure Ventilation: Due to the relatively constant volume nature of the design, the air systems are designed to have ultra low pressure drops and hence reduce fan energy consumption to an optimal level. In particular the air handling units are configured to allow high pressure drop components to be bypassed when not in use and AHU elements are sized for 350fpm face velocity. Low duct velocities (1200fpm) mains and 0.08”/100ft in branch ductwork) are intended. • Perimeter Baseboard Hydronic Heating: Where no underfloor air distribution or overhead system is in place at the perimeter (e.g. fully naturally ventilated perimeter zones), the heating requirement may be provided by perimeter convective radiators. • Embedded Hydronic Radiant Cooling (Radiant Floors): Cross-linked polyethylene tubing will be embedded in select areas such as the business center, café (faculty building) and the dining pavilion, to temper the indoor envi-ronment (not a full conditioning strategy). • Hydronic Radiant Ceiling Panels (Chilled Ceilings): Hydronic backed metal ceiling panels will be installed in identified areas in order to comfort condition the space. • Hydronic Radiant- Radiant & Convective Cooling (Chilled Sails/ Passive Chilled Beams): Hydronic chilled beams without active airflow and hydronic backed metal ceiling panels will be installed in select interior office areas in order to comfort condition the space. The passive beams use natural convection to provide cooling to the space by drawing warm air though the coil, cooling it and directing it into the occupied space below. When passive chilled beams are used, ventilation air must be supplied to the space through a separate system. Typical cooling capacity of 155 (BTU/h)/ft can be expected from a passive beam, capacities vary depending on room conditions and fl ow rates. • Inductive/ 2-sided discharge (Active Chilled Beams): Hydronic backed 4-pipe chilled beams are designed for spaces with high cooling loads as well as perimeter conditioned zones. The chilled beam is designed for integration into suspended ceilings made from metal, gypsum plasterboard, mineral fibre board, etc. • Indirect Evaporative Cooling: To reduce the demand on active cooling systems the air systems incorporate evaporative cooling, thereby taking advantage of Stanford’s relatively dry climate during the cooling dominated summer months.Stanford GSB 8/03/07 100% SD Mechanical Narrative Page 4 of 15 4. Energy Recovery • Heat Recovery: Where possible, cost effective, and safe, air systems incorporate heat recovery via heat pipes. • Mixed Air System: Where ventilation requirements are low, re-use of conditioned building return air through air handling unit mixing will be employed. • Make-up Air Use: Where appropriate, make-up air from adjacent spaces is used in lieu of additional supply air (e.g. restrooms,
View Full Document
Unlocking...