The stated 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 a roof/ceiling assembly with an STC rating of 50. Our elementary school has been designed to meet a maximum background noise level in classrooms and other primary learning spaces of 45 dBA using careful selection of a planned development site that has low outdoor sound levels. The background noise level in classrooms and other primary learning spaces is calculated with windows maximized for daylighting and views, and a roof/ceiling assembly with an STC rating of 40. Will a roof/ceiling assembly that has an STC rating of 40 be acceptable to achieve EQp3 if the project can achieve the LEED goal of a maximum background noise level in classrooms and other core learning spaces of 45 dBA?
The cost impact for increasing a roof assembly from STC 40 to STC 50 can be significant, and the STC 50 roof is over-designed for a quiet site. If the site Ldn (day-night average sound level) or peak Leq (hourly equivalent sound level) is verified to be lower than 60 dBA the STC 40 roof will be acceptable, with a qualification for mechanical noise as noted below. Rooftop mechanical equipment is frequently a significant source of interior noise, and this noise impact may be increased by a lighter weight roof assembly. The roof and mechanical system design must be adequate for providing the required interior noise level, regardless of the roof STC rating. Interior noise impacts from future increased noise levels will typically be controlled by window acoustical performance for most noise sources. Although designers are required to consider future noise levels, mitigation for future noise sources that result in interior levels above 45 dBA will probably require upgrades for windows and possibly for the roof, depending on the noise exposure. *Initially, an earlier version of this ruling was posted. It has been since amended by the EQ TAG.* Applicable Internationally.