The building is a 144 unit apartment building in the District of Columbia. The proposed design would utilize natural ventilation from the exterior windows and doors with operable areas equal to or greater than 4% of the floor area with all areas to be ventilated permanently open to the rooms with operable windows or doors. However, all spaces to be ventilated are not within 25 ft. of the operable wall openings. The prerequisite requires meeting ASHRAE 62.1 2004 Sections 4-7. Section 5.1 of the ASHRAE standard has an exception that states "An engineered natural ventilation system when approved by the authority having jurisdiction need not meet the requirements of section 5.1.1 and 5.1.2." ASHRAE 62.1-2004 does not define what an "Engineered Natural Ventilation" system is. The system we propose above meets the requirements of the 2003 International Mechanical Code accepted by the local jurisdiction (the District of Columbia). Does it therefore qualify for the exception in section 5.1 of ASHRAE 62.1-2004 -- and meet the LEED prerequisite?
The project may use natural ventilation as the only source of outside air only if it can demonstrate, using acceptable engineering calculations or multi-nodal bulk airflow simulation, that under still air conditions, the units will satisfy the requirements of Appendix E Table 2 for residential facilities.