Overview
P2S was contracted to handle the mechanical design of a new 95,000 GSF science building on the California State University Long Beach campus. The new building houses Anatomy, Physiology, Biology, Biochemistry and Organic Chemistry research and teaching laboratories. These laboratories include over 150 fume hoods, Class II Type B3 biological safety cabinets, hazardous chemicals and cold storage rooms.
Challenge
University laboratory buildings have traditionally been the largest consumers of energy. In fact, the EPA has identified that laboratories consume 5 to 10 times more energy per square foot than typical office buildings. Cal State Long Beach set a fundamental goal to design a highly energy efficient laboratory building while providing a high standard of safety, health and comfort for the building occupants.
By employing an integrated design approach, the entire design team can focus on key project goals. Laboratory buildings offer many opportunities to improve energy efficiency by reducing cooling and heating loads through the use of energy efficiency glazing, efficient lighting (<1W/ft2), and effective use of daylighting. Plus, adequate space for HVAC duct and shaft locations can allow for efficient supply and exhaust ducting with minimal fittings.
Action
P2S led the design team to pursue a whole-building approach including utilizing numerous HVAC energy efficiency features that would be of potential interest to other campuses:
Manifolded Variable Air Volume:P2S engineers utilized variable air volume control for both the supply and exhaust systems in the building. Four variable air volume air-handling units supply air-conditioning to the building. With two separate cooling coils in each. All four units provide two separate cold decks. One cold duct from each unit supplies the Chemistry labs. This configuration was strategically designed to allow:
- supply ducts serving the Chemistry labs to operate at a higher supply air temperature since they require more ventilation airflow due to the relative high quantity of fume hoods in these labs
- reduced cooling loads and reheat requirements
- more diversity in unit sizing resulting in smaller air handlers by grouping both spaces on the same air handlers
- reduction in Cooling Loads and Airflow Required: P2S’s whole-building approach reduced cooling loads further by designing a highly efficient building envelope and lighting system.
- heat from high wattage laboratory equipment to be grouped and exhausted to minimize impact on space cooling loads when appropriate
- reduced cooling requirements in unoccupied office spaces by using occupancy sensors
- fume hoods utilize sash stops at 18” to promote lower sash heights during operation.
- lower fume hood face velocity to 60 fpm when nothing is in front of fume hood by using fume hood zone presence sensors
- reduction in airflow, cooling and reheat requirements by cascading air from the offices as make-up air to the laboratories
Low-Pressure Drop Design:Because fan energy can account for as much as 45% of the electrical energy consumption in laboratories. P2S implemented the following strategies to reduce fan energy:
- 70% airflow system diversity for VAV systems
- Direct duct routing and 1,500 fpm maximum velocities in duct mains to minimize duct pressure drops
- 350 fpm airflow velocities for coils and filters to reduce system static pressure
Right-Sizing Equipment:P2S offset energy monitoring and state-of-the-art laboratory controls systems costs with the capital cost savings of right-sizing the HVAC equipment and corresponding electrical systems. We used a 70% airflow diversity factor to size the variable volume exhaust fans and supply air systems. After occupancy, the trends show the building operates with an airflow diversity of 50-60%.
Energy Monitoring and Control Systems:The entire building is fitted with direct digital control and utility metering, including electrical, gas, chilled water and hot water systems. The building energy management system controls the HVAC systems and communicates with the laboratory HVAC control systems controlling the zones. All supply and exhaust fans are fitted with variable frequency drives this allows the manifolded exhaust fans to be staged while fan speeds are adjusted to maintain minimum stack discharge velocities at 3,000-fpm.
Results
The performance of the HVAC systems in this building has pleased the University. The project received awards for the UC/CSU Sustainability Best Practice Award for HVAC Design, Innovative Control and Energy Information Systems and the Association of Energy Engineers Energy Project of the Year Award.
Since the initial occupancy, the campus has recorded operating data and energy usage. The laboratory building uses less energy (161 Btu/ft2-yr) than even some of the other non-laboratory buildings on campus. And with flexibility in the design, control strategies can be further optimized now that the building is fully occupied.
