Consulting-Specifying Engineer - December 2007 - (Page 25) Version 2 requirements, the design process also adhered to ASHRAE 90.1-1999 for energy efficiency, ASHRAE 55-1995 for thermal comfort for human occupancy, and ASHRAE 62.1-2001 standard for ventilation. The main incentive for the new building was to achieve a substantial energy use reduction when compared with the firm’s existing facility in Guaynabo. Conserving energy Energy conservation measures incorporated into the design including: • Lighting upgrade: With an illuminationlevel calculation program, and using minimum illumination level requirements of 50 lumens at all desktops, the total Watts per square foot were reduced by 0.78 W/sq. ft. In addition, all offices and open areas have T8 lamps with high-efficiency tubes and occupancy sensors. All walls have a reflec- tivity of 75% and ceilings have a reflectivity of 85%. • Insulation upgrade: In addition to the minimum requirements of ASHRAE 90.11999, the roof insulation was increased from R19 to R30 with a reflectivity of 92% and the walls from U = 0.58 and no R value requirement to a U = 0.089 and an R11.25. • Condensing unit efficiency upgrade: R410A units with dual speed compressors and 60,000 Btuh capacity with an 11.35 EER were installed (ASHRAE 90.1 minimum requirement is 9.7 EER). • Heat recovery: An energy recovery unit (enthalpy wheel) with an 85% efficiency and capable of handling 125% of the required outside air was included in the system. In addition, the hot water for the reheat coil in the air conditioning units is obtained from desuperheaters for each of four compressors. Solar panels are connected in series for additional reheat capacity. • High efficiency fans: The air conditioning unit has an adjustable-pitch vane axial fan with a static efficiency greater than 75%. ASHRAE 90.1 requires a maximum of 1.7 hp per 1,000 cfm for variable air volume (VAV) systems. The design used 0.675 hp per 1,000 cfm. • Fenestration: Double glass windows with clear glass inside and low-E glass outside with U = 0.26, exceeding ASHRAE 90.1 requirements. In addition, exterior metal shadings cover all glass areas for a substantial improvement on the solar heat gain coefficient requirements. • Exhaust and supply fans: The building exhaust and the outside air make-up use the fans of the energy recovery unit and are both served by variable frequency drives for higher energy efficiencies. Natural ventilation makes this library coolest building on campus rchitecture rules at this new Judson University building, which houses an expanded library and the division of art, design, and architecture. “Seeking a facility worthy of an evolving architecture program that is seeking accreditation, the university conducted an international design competition,” said Norm Bower, KJWW public relations coordinator. London-based architect Alan Short of Short and Assocs., a pioneer in low-energy, naturally ventilated, and passively cooled buildings, designed the facility. The design team’s challenge was to treat light and humidity issues in a library and art environment, where these factors could seriously damage the contents of the 88,000-sq.-ft building. Dominant energyconscious features of the building are its photovoltaic, natural ventilation, and natural daylighting systems. Optimizing solar gains in the spring and fall is intended to allow the building to run naturally, with little or no mechanical intervention, for six or more months of the year. The building is expected to earn a USGBC LEED silver rating. “The greatest challenge as an HVAC engineer on this project was taking the vision of placing a naturally ventilated building in the middle of the Midwest,” said Wade Ross, PE, lead mechanical engineer on the project. “Although the system works well in Northern Europe, we had to not only adapt it to the harsh Midwest climate, but also justify its viability.” Ross also points to the vital need for teamwork. “Another struggle for the engineering firm was to design an exterior concrete precast structure with multiple openings. Extremely close coordination had to take place between engineering disciplines, architect, and the precast contractor,” he said. Designing a naturally ventilated building that conformed to local code also challenged the team. For example, when it came to smoke A Harm A. Weber Academic Center Judson University Elgin, Ill. MEP Engineer: KJWW Engineering Consultants, Rock Island, Ill. Silver Winner evacuation strategies, “computational fluid dynamics analyses were commissioned to show that smoke could be effectively vented from the structure,” said architect of record Rick McCarthy, AIA, of Burnell Cassell Assocs., Elgin, Ill. Natural ventilation is probably the most innovative aspect of the design. The building draws cool air at the lower level, circulates it throughout the building through various routes, and exhausts the air through roof terminals. Because of the extreme Midwest climate, a fully natural ventilation system was not possible. Consequently, mechanical engineers designed a hybrid system that minimizes the use of conventional heating and cooling, with operation in the natural mode for as much of the year as possible, but engaging the mechanical mode when the need arises. There is a significant amount of engineering involved in the design of such a system, and the end product is a building that behaves as a single integrated system. Photography courtesy of KJWW Engineering Consultants. Consulting-Specifying Engineer • DECEMBER 2007 25
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