Special Environmental Considerations

• SLOPED ROOF OPTION. To provide better protection from roof leaks, the project budget should support the added cost of a sloped, standing seam metal roof, rather than a flat built up or membrane roof system.
• WINDOW LIGHT AND UV CONTROL. The budget should support treatments to the windows to control light and UV intrusion. For new glazing this generally indicates at least the use of 0.060" PVB-laminated glass for UV control.
• DUCT SYSTEM. A major HVAC cost driver for the collection spaces in the project will be the duct system. It should be an unlined, externally insulated or double-wall duct system. The system should be a multi-zone duct system, where each zone's supply air duct makes a separate home run to its respective air-handling system, requiring no piping over collection spaces. This will result in a lower-than-typical space efficiency (net-to-gross) due to the added duct space, and a greater-than-typical poundage of ductwork due to the added low-pressure ducts.
• FULL-FEATURE CONSTANT-VOLUME REHEAT SYSTEMS. The budget should allow for the HVAC systems as full-feature constant-volume reheat systems, including:
  • a. hot water reheat coils and humidifiers for each air handler, with these system elements located only in mechanical rooms;
  • b. cooling coils sufficiently deep to provide effective dehumidification, usually requiring 6- or 8-row coils with no more than 10°F coil approach; or, use of a desiccant system to pre-treat the outside air;
  • c. separate outside air pre-cooling coil.
  For more economical operation, the air handlers might be upgraded to multi-zone units, with the added cost of the hot-deck and mixing damper section. (The unit would actually be operated as a bypass or "Texas" multi-zone system, and would not actually have a coil in the hot deck.)
  Economizer and enthalpy economizer systems will not be required, and the systems should be designed to introduce a minimum volume of outside air.
• GASEOUS POLLUTION CONTROL. The project budget should include the costs for selected gaseous pollution control equipment, or the provision of racks or frames for the addition of the equipment later. The budget should also include costs associated with the higher fan pressures required (fan, motors, etc.).
• HIGH-EFFICIENCY PARTICULATE FILTERS. Project cost should include high-efficiency filters and associated higher fan pressure costs (fan, motors, etc.).
• DESICCANT SYSTEMS. The budget should allow for the added cost of the desiccant systems, and the possible costs associated with using indirect-fired natural gas for regeneration (piping, flues, etc.).
• FULL-FEATURE DIRECT DIGITAL CONTROL (DDC) SYSTEM. The design budget should support a full-feature DDC system, including training and all commissioning services.
• CHILLER PLANT. The budget should provide for an appropriate chiller plant and chilled water piping. The budget should allow the chillers to have features for satisfactory part-load performance. A storage tank may also be required for more efficient and stable low-load operation.
• WATER-SIDE ECONOMIZER. The engineer may also wish to have a water-side economizer for more economical cooling in winter. This will usually require a winterized cooling tower, a plate-and-frame heat exchanger, and some additional valves and piping.
• CONDENSER HEAT RECOVERY. The engineer may wish to provide free reheat through the use of a heat-recovery chiller. This will usually require a plate-and-frame heat exchanger, and some additional valves and piping.
• HUMIDIFICATION STEAM SYSTEM. The budget should support a dedicated humidification steam system, using Dri-Steem "Ultra-Sorb" humidifier manifolds. The humidifiers should be fed from a common pressurized steam piping system fed from a gas-fired boiler, with schedule-80 or better condensate return piping. Canister, electrode or evaporative pans should not be used. The project budget should also support water treatment appropriate for the local water issues.
• CONSTRUCTION VENTILATION AND SYSTEM BREAK-IN. These phases to the construction in preparation for occupancy will increase the project cost. The costs include the additional cost of implementing the ventilation (fans, air flow maintenance, added labor), and the added project time for system HVAC break-in before moving in collections.
• COMMISSIONING. The project budget should also support a system checkout as described in ASHRAE Guideline 1-1989, "Guideline for Commissioning of HVAC systems." This service will be provided by an outside commissioning firm.
• PRE-MOVE IN CLEANING. The project budget should include the cost of having all the spaces cleaned with a HEPA vacuum just before occupancy.
• COLLECTION CLEANING. The cleaning of the collection before moving in is required and can be a significant cost, either as a contract item or in additional staff time.

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