In order to obtain this credit, does this apply, and if so to what extent does this apply, to school science lab classrooms? School science classrooms sometimes function as "labs" in the sense that chemical experiments where potentially hazardous chemicals are used are done under chemical safety hoods, which are exhausted to the outdoors. These hoods are usually operated at night to maintain the hood interior under negative pressure. Chemicals are stored in cabinets in separate rooms, (prep rooms). Sometimes, however, the classrooms are used for non-chemical-using subjects, such as physics. The questions are: 1. Do all science classrooms fall under this classification? In order to apply for this credit do we need to exhaust classroom labs? Do we need to exhaust the classroom lab if it has no chemical safety hood (examples are physics lab, earth science lab, biology lab, etc.) If distinctions can be made, to what extent must the uses of these rooms be prescribed? 2. Do the prep. Rooms fall under this classification? (Again in order to apply for this credit do we need to exhaust these rooms? Please be aware that the students usually do not have access to these rooms. They are usually locked, and any chemicals are in safety cabinets.) 3. If any of the above applies, can the exhaust rate of 0.5 cfm be reduced during unoccupied periods, such as night and week ends in order to minimize energy usage? If so, should the higher level of exhaust be tied to occupancy sensors, on a timed cycle, or manually operated?
On page 280 of the LEED-NC v2.1 Reference Guide, under Design Approach it is noted that projects should "physically isolate occupant activities associated with chemical use through proper design". 1. Based on your narrative, the school science classrooms (or laboratories) with chemical safety hoods will provide negative pressure inside the hoods. It would also be reasonable to have the "lab" as a whole under negative pressurization. The fume hoods will most likely operate only when there is an experiment underway but for all other times having the whole lab being maintained at a negative pressure will ensure that no hazardous chemicals or fumes escape out and undermine the air quality. For EQc5, you may exclude science classrooms or regular-use classrooms that are used for non-chemical demonstrations only and that do not involve potentially hazardous chemicals. 2. The same would apply to prep rooms. Though these areas are not accessible to students, school staff will be using them and the impact on occupant health needs to be addressed. 3. All areas where chemical usage occurs must be maintained at the 0.5 cfm/ft2 exhaust rate at all times to exclude the possibility of any potential chemical fumes build up. The intent of this credit is to provide a safe and healthy indoor environment for all users, and maintaining this exhaust rate will contribute to achieving this goal. The energy penalty incurred is minimal when compared to the health benefits it affords. Note: to comply with EQp1 - and thus ASHRAE Standard 62.1-2004 - "science-lab classrooms" must include at least 1 cfm/ft2 exhaust airflow; make sure you consider these two credits simultaneously. Also check with the local code officials as appropriate for definitions and requirements that may affect this discussion. Applicable internationally.