The intent of this prerequisite to "Provide classrooms that are quiet and in which teachers can speak to the class without straining their voices and students can effectively communicate with each other and the teacher." Per the prerequisite, this is accomplished by meeting prescriptive requirements for the building envelope and interior assemblies, with the goal of achieving a maximum background noise level in classrooms and other primary learning spaces of 45 dBA. The prerequisite has a prescriptive standard that would require the corridor/ classroom assembly to have an STC rating of 45. The fundamental goal of this project is to provide small group instruction (SGI) spaces that are readily accessible/ adjacent to the "main" classrooms. To achieve this, small group instruction spaces have been provided as part of an "expanded" corridor. It is vital to the curriculum that these corridor SGI\'s be both visually and physically accessible to the classroom; in our case via 8\'-0" wide and 8\'-0" high fixed glazed systems for base bid and operable glazed partitions as an alternate. By providing these fixed or operable partitions between the classroom and "corridor SGI\'s", the effective area of the classroom is expanded, providing more one on one instruction space for students without effectively "removing" them from the classroom environment. It is anticipated that these partitions will be open approximately 50% of the time. The classroom, corridor and corridor SGI will all part of one acoustic zone at least half of the time. The glazing size is required to maximize the inclusion of students into the normal flow of the main classroom. In essence, we have an open classroom design that will not meet the goal of 45 dBA inside the classroom. Will this design be exempt from this prerequisite? If not, what provisions need to be made to address this design issue? This concern is echoed in ANSI S12.60-2002, Annex D2.2. It appears this prerequisite is in direct conflict with the project\'s fundamental curricular goal and is prohibiting the achievement of LEED Certification. Finally, the School District has elected an exterior wall assembly that utilizes 2" rigid foam plastic insulation on the exterior side of the metal stud cavity in lieu of other insulation systems designed to be located in the metal stud cavity (i.e. fiberglass batt insulation, blown-in cellulose, etc.) The primary reason is so the dew point is located outside of the metal stud cavity, which eliminates the potential for mold growth associated with interior stud cavity insulation systems. We cannot achieve an exterior wall assembly STC of 50 with the 2" rigid foam plastic insulation system. Will the 2" rigid foam plastic insulation wall assembly STC be approved to meet the intent of this prerequisite?
The CIR is asking about two separate areas, the use of small group instruction (SGI) corridor spaces, and the STC ratings of exterior assemblies. The question will be addressed in the order that they were presented. The SGI spaces, as described, do not appear to meet the intent of the prerequisite. It is unacceptable to have a large, direct path for noise to travel between classrooms and corridor spaces, especially given that it will likely be open 50% of the time. This presents a high probability that noise will be able to travel between classrooms. Additionally, the potential for significant noise transmission between SGIs in the same corridor (each associated with a separate classroom) was not addressed. The design does not seem to be providing learning environments that minimize acoustical distractions. If the design team is concerned that their project will not be able to meet the requirements of ANSI Standard S12.60-2002, Annexes B-D, it should be noted that there is an alternate compliance path which allows for the use of the 2003 HVAC Applications ASHRAE Handbook in lieu of the S12.60 Annexes B-D requirements. Please see the LEED for Schools Reference Guide prerequisite description for more information on this compliance path. A LEED for Schools EQp3 CIR ruling dated 12/19/2007 allows for design teams to utilize exterior assemblies that do not provide a STC 50 rating, provided that the site Day-Night Average sound level (Ldn) is verified to be lower than 60 dBA, and mechanical equipment noise attenuation is specifically addressed. Please see this CIR ruling for further information. Applicable Internationally.