Medical Construction & Design (MCD) is the industry's leading source for news and information and reaches all disciplines involved in the healthcare construction and design process.
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field. A unique factor in these projects is: no heating boilers. Dedicated steam boilers satisfy humidification and sterilization loads. Key concept: Capture as much thermal assets from return and exhaust air as possible. The Dual Air Path concept processes outdoor air separately from return air before combining the two conditioned air streams as supply air. Exhaust air and outdoor air streams exchange heating and cooling energy during all seasons. The separate return air path provides a consistent cooling load to operate heat pump chillers on a 12-month basis near peak efficiency. Total purchased annual heating and cooling energy (and cooling tower water use) is dramatically reduced. In climates characterized by low moisture content outdoor air — think western U.S. — distributed heating and cooling strategies that turn away from power-consuming cold-air distribution are generating interest. Arash Guity at M+NLB Engineers describes a displacement ventilation strategy that involves floor-level delivery of low velocity, dehumidified outdoor air to patient rooms. Thermal loads create vertical air plumes that carry heat and particulate matter upward and out through ceiling or high-wall exhaust www.mcdmag.com registers. Ceiling level temperatures at 80 F or higher yield nearly conventional supply/return temperature rise and radiant elements satisfy the balance of heating or cooling needs. Dramatic reductions in fan and reheat energy are possible. Michael Sheerin, healthcare principal at TLC Engineering for Architecture, is quick to state that large hospital thermal plants benefit from the Dual Path air conditioning approach coupled with heat pump chillers. Large capacity centrifugal heat pump chillers satisfy thermal loads that align for a significant number of annual operating hours. The capacity — and cost — of conventional chiller and boiler components is reduced even when earth coupling may be impractical because the site area is insufficient for a well field or evaporative lake. In the not too distant future, a hospital and its operators will become the last one with a dinosaur thermal plant. Forward-thinking designers, owners and operators are preparing for the fundamental change that is transforming hospital thermal comfort systems. James Moler's more than 30 years of experience began with a mechanical contractor, where he developed innovative mechanical solutions for nationally significant projects, including in healthcare. He is a LEED Accredited Professional with BD+C Specialty and a member of the Green Guide for Health Care Steering Committee. January/February 2013 | Medical Construction & Design 53