Our project is an Environmental Studies Building on a community college campus in California. The building is two stories and roughly 22,000 square feet. It is divided into two wings - one of which is mechanically ventilated with an underfloor system and one of which is naturally ventilated. The naturally ventilated wing is roughly 9,000 square feet and includes some classroom space, tech support areas for the classrooms, and open study and lounge space. We do not have any questions about how this credit applies to the "mechanically ventilated" wing. For the Naturally Ventilated spaces, we would like to know what methods we can use to show compliance with the requirements for this credit. We have heard some reference that a simulation run is not the only acceptable path to validation/documentation, one alternative being a detailed airflow diagram and accompanying narrative and related cutsheets based on established principals of natural ventilation. However all of the official language in LEED Version 2.0 and 2.1 appears to point to a "simulation" requirement. We believe that the credit\'\'s intent to "provide for the effective delivery and mixing of fresh air to support the health, safety, and comfort of building occupants" can be met without a "simulation" run being undertaken but would like confirmation as to whether or not this is the case. If a simulation is required, it will add significant cost to the project. The question is: What of the following (alone or in combination) will the USGBC accept as validation that the project meets the credit intent (the following has been listed in increasing order of effort/cost). 1) Conformance with Title-24 requirements for a naturally ventilated space - Section 121(b)1 The code reads: "Natural outdoor ventilation may be provided for spaces where all areas of the space are within 20 feet of an operable wall or roof opening through which outdoor air can flow. The sum of the areas of the openings must total at least 5 percent of the floor area of each space that is naturally ventilated. The openings must also be readily accessible to the occupants of the space at all times. Air flow through the openings must come directly from the outdoors; air may not flow through any intermediate spaces such as other occupied spaces, unconditioned spaces, corridors, or atriums. High windows or operable skylights should be accessible from the floor." 2) Airflow diagram(s) based on established principals of natural ventilation 3) Narrative based on established principals of natural ventilation 4) A single-node based simulation using our own internal software that would then provide air change rates for the space (but not air diffusion effectiveness). 5) A multi-nodal cfd based simulation 6) Some other method not listed above We appreciate your clarification on this topic.
The California Title 24 requirements for naturally ventilated spaces (very similar to ASHRAE 62 requirements for naturally ventilated spaces) are appropriate for documenting compliance of a naturally ventilated building with EQ prerequisite 1, but not for documenting achievement of EQ credit 2. The best way to demonstrate ventilation effectiveness in a naturally ventilated building is to develop a multinodal model of airflow. However, a convincing narrative using demonstrated natural ventilation principles, and including diagrams accurately representing the spaces in question, and supporting calculations based on space characteristics could be used to demonstrate achievement of this credit. Such a narrative would need to be well crafted, clear, and convincing. A single node model could be used to support this evaluation, but by itself would not be adequate to demonstrate achievement. Applicable Internationally.