University of California, San Diego, Center for Molecular Medicine East
(Laboratory Airflow Control System Re-Commission):
The University of California, San Diego Center for Molecular Medicine East (UCSD CMME) building has over 40,000 net square feet of lab space, and had over 135,000 CFM of single-pass (non-recirculated) supply air serving the laboratory areas through five (5) separate air handling systems. Similarly, there are four exhaust fans (two exhaust plenums, each with two exhaust fans) serving the lab areas.
The air handling systems include chilled water coils to distribute 55ºF air through the duct to the zone level, where the air volume is regulated by manual balancing dampers. A reheat coil reheats the air as required to maintain a comfortable temperature in the space.
We began the CMME project by evaluating the building for two possibilities: 1) convert the constant-volume (CV) air supply system to a variable air volume (VAV) system, or 2) re-balance the CV building to a reduced volume for energy savings. Although the VAV conversion was a very attractive offering, the decision was made to rebalance the building to a reduced airflow volume.
We engineered a solution to do this re-balance work. Every room in the lab area was evaluated for energy savings. When evaluating a room as a candidate, we had to look at its existing airflow volume, and decide whether we could safely reduce that volume. Rooms with high process loads (e.g., chemical fume hood exhausts and canopy exhausts) were not reduced in volume, nor were rooms with high heat loads. Eventually we evaluated 185 rooms with 391 diffusers, 165 exhaust grilles, 40 fume hoods, and 5 exhaust canopies. Our evaluation of system performance looked at safety parameters (proper fume hood and room pressurization control), thermal comfort, and energy efficiency of the systems.
Newmatic Engineering performed a thorough re-commissioning of the CMME Building in light of recent revelations that heat loads in laboratories are not nearly as high as engineers had been assuming. While numbers in the range of 10 to 30 watts per square foot had been used for heat loads, empirical studies at a UC campus have shown that the actual heat loads are closer to 1 to 3 watts per square foot. As such, lab air change rates can be reduced dramatically.
In this process, Newmatic Engineering developed new airflow rates for each diffuser and exhaust grille, all the time evaluating room pressure control (to maintain proper pressurization relationships), building pressure control (since the building had slightly too much exhaust), fume hood capture and containment, and proper thermal comfort.
In the final analysis, we calculated the total annual energy costs saved by the re-engineering and facility rebalance effort to be approximately $330,000 per year. This equates to annual energy savings of 2,557,000 kWh and 118,400 therms with a peak kW reduction of 292 kW.