Modeling low flow fume hoods in a Lab

Laboratory systems are covered by Appendix G and therefore are not process loads, so energy savings are possible as long as you follow the modeling protocol for the Baseline systems. Here are some notes specific to 90.1-2007: -Exception (d) to Section G3.1.1 requires modeling of system #5 or #7 in Baseline with 50% reduction in exhaust and makeup air volumes during unoccupied periods (for laboratory systems with minimum of 5,000 cfm of exhaust). The User's Manual Appendix G laboratory schedules appear to indicate that this refers to the fume hood being unused (i.e. sash closed), and not to the whole building occupancy conditions. -G3.1.2.10 Exhaust Air Energy Recovery - exception (h) exempts labs with 5,000 cfm of exhaust (i.e. the systems modeled as Baseline per Exception (d) G3.1.1 from requirement for energy recovery in the Baseline). -Table 6.5.3.1.1B Fan Power Limitation Pressure Drop Adjustments include a fume hood exhaust exception (-1.0 in. w.c. adjustment). This means when applied to the laboratory system's supply fan power limitation, the Baseline calculation must apply the -1.0 in. w.c. adjustment, and the fume hood exhaust fan power is separated from the system and modeled as unregulated process energy, with the same W/cfm as that of the Proposed Case. Credit may be taken from improved motor efficiency. Addendum p to 90.1-2007: -Removes the fume hood exhaust exception within Table 6.5.3.1.1B as noted above, and adds two new device credits, one for exhaust system serving fume hoods (0.35 in. w.c.) and laboratory and vivarium exhaust systems in high-rise building (0.25 in. w.c./100 ft of vertical duct exceeding 75 ft) -Modifies pressure credit for "fully ducted return and/or exhaust air systems" from 0.5 to 2.15 in. w.c. for lab and vivarium systems