Send in the engineering troops: HVAC and plumbing
Military facilities present an army of challenges—exacting codes and regulations, stepped-up security issues, and budgetary concerns. HVAC, ventilation, and plumbing systems are discussed.
- Kevin D. Bomboy, PE, LEED AP, Chief mechanical engineer, STV Group, Douglassville, Pa.
- David Callan, PE, CEM, LEED AP, HBDP, Vice president, McGuire Engineers Inc., Chicago
- Robert L. Crance, Mechanical engineer, Black & Veatch, Overland Park, Kansas
- Joseph H. Talbert, PE, ARM, Project manager, Aon Fire Protection Engineering, Lincolnshire, Ill.
- William Valdez, Northwest justice and civic sector leader/principal, DLR Group, Seattle
CSE: What unique requirements do HVAC systems in military facilities have, and how have they changed in the past 1 to 2 years?
Crance: HVAC systems for military facilities do have unique requirements associated with providing a minimum level of protection from certain threats for the occupants of the facility. HVAC systems must be capable of maintaining positive pressurization during normal operation scenarios as well as being capable of whole-building isolation to provide shelter-in-place capability. Although the base requirements for system performance have not changed recently, the control practices and components required to achieve the expected performance have become more common and accepted. A military facility often has unusual design and operational criteria associated with the specific mission objectives it supports.
Bomboy: There is a requirement to be able to isolate the air intake system via dampers in the event that a CBR attack would occur. This is manually activated through an emergency response push button.
CSE: Describe the use of fans and ventilation equipment in a recent military facility project.
Bomboy: Typically the ventilation is achieved using a dedicated outside air system (DOAS) with an energy recovery wheel. Energy is captured from the building’s exhaust systems, such as toilet exhaust, and transferred to the incoming ventilation air without actually mixing the two airstreams. In spaces that don’t require strict temperature control, ventilation fans can be used to gain free cooling.
CSE: Have low-flow plumbing fixtures become the norm in your military facility projects?
Crance: Low-flow plumbing fixtures have become the expected standard of design for our recent military facility projects. Project requirements establishing water use reduction expectations for new construction to achieve LEED Silver certification are driving the use of low-flow fixtures. Advances in product performance and a growing understanding of the required operation and maintenance of these fixtures are making use of low-flow fixtures acceptable to nearly all project end users. The use of low-flow fixtures is also extending the available capacity of treatment, distribution, and collection systems at certain installations.
Bomboy: Low-flow fixtures have become the standard in all facility designs, including military facility design. Low-flow toilets with dual-flush options are commonly used. Waterless urinals are gaining acceptance in military design. Low-flow showers and sinks are standard design as well as sensors that only turn on the water on the sinks when hands are under the faucets. Rain water and gray water harvesting for use in flushing toilets is becoming more cost-effective.
CSE: Discuss chiller and/or boiler plants in a project you recently worked on.
Bomboy: The use of multiple high-efficiency condensing style hot water boilers is a common practice to achieve maximum efficiency. This is teamed with a boiler control system that sequentially stages the boilers “ON” to achieve the maximum efficiency. Chilled water system designs are using multiple air-cooled chillers. Air-cooled chillers have low maintenance and do not require makeup water and chemicals as do water-cooled chillers and cooling towers. Another recent trend is to use chillers with magnetic drive compressors, which have high efficiency and have reduced maintenance requirements. Recent chilled water plants have been designed to support mission critical operations. The significant challenges for these systems include providing high system availability, high energy efficiency at varying load conditions, and first costs aligned with program budget constraints. The chilled water plants have successfully incorporated use of condenser water economizer capability, condenser water free cooling capability, heat recovery capability, and modular design strategies. The use of variable flow chillers and variable flow distribution networks has also helped these projects achieve their energy use goals. Cooling tower storage basins and chilled water storage tanks are used to achieve system availability requirements.