©2014 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 56, no. 4, April 2014.
By David Shumway, P.E., Member ASHRAE
About the Author
David Shumway, P.E., is the mechanical engineer of record and commissioning authority for the new Alaska Scientific Crime Detection Laboratory in Anchorage, Alaska
The new Alaska Scientific Crime Detection Laboratory is a modern two-story 84,410 ft2 (7482 m2) state-of-the-art crime lab in Anchorage, Alaska. The facility is arranged in two wings with a large central two-story main entry, lobby and faculty dining area serving as its architectural focal point. The facility includes many specialized forensic laboratory suites, a ballistics suite with dedicated indoor firing range, secure evidence storage areas, training classrooms/labs and administrative support offices. Project design began in 2006 with the facility officially opening for business in 2012. User satisfaction is very high and operations and maintenance personnel are pleased with the HVAC systems, their arrangement and performance. The design conforms to the requirements of the 2004 versions of ASHRAE Standards 55, 62.1, 90.1 and the ASHRAE Laboratory Design Guide.
Laboratories have a well-deserved reputation for consuming large amounts of energy, especially in cold climates. The ASHRAE Laboratory Design Guide was implemented extensively to help reduce energy use while maintaining a safe work environment for its occupants. Both supply and exhaust ventilation systems use variable air volume control. Exhaust airflow rate is controlled to maintain the desired ventilation rate in air changes per hour (ach). Supply airflow rate is offset from exhaust airflow rate to provide precise room pressure control.
The facility uses three separate manifolded laboratory exhaust systems. Types and concentrations of chemicals used, lower first cost, fewer stacks, simple connection to exhaust air heat recovery and excellent exhaust air dilution made this the logical system choice for this laboratory application.
Runaround loop heat recovery coils were implemented for each of the three separate 100% outdoor air laboratory ventilation systems. This heat recovery method was selected to eliminate any concerns with cross-contamination. Each exhaust air heat recovery coil is preceded by a MERV 8/MERV 13 filter bank. Filter air pressure drop is monitored through the central building automation system (BAS) to ensure the coils are maintained clean for maximum energy savings.
Toilet rooms, janitor closets and other spaces requiring 100% general exhaust ventilation were tied into the laboratory exhaust fan systems using exhaust air control valves; eliminating many small exhaust fans and allowing the runaround loop heat recovery systems to recover as much general exhaust air energy as possible before leaving the building.
Six modular, high efficiency, fully modulating, gas-fired boilers provide precise hydronic heating control with a minimum turndown to 8% of the building’s design heating day load. Variable-speed drive hydronic heating pumps precisely match system flow with heating demand.
Energy analysis software package eQUEST v3.61 was used to model the facility’s annual energy consumption. The HVAC system was zoned and modeled based on the actual architectural building envelope to the maximum extent practical. Composite U-values were calculated from the many detailed architectural roof, wall and floor cross sections. Heating and cooling system input was very representative of the actual mechanical design. Lighting levels and control features were modeled for each room based on building wide averages. Estimated plug and task lighting loads were combined and applied equally throughout the building.
Utility energy consumption data for 2012–13 was collected for comparison to energy model predictions. Results show an over prediction of electrical energy and demand and an under prediction of fuel gas usage. Overall agreement is good.
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