Rating System

LEED BD+C: New Construction, LEED BD+C: Schools, LEED ID+C: Commercial Interiors, LEED BD+C: Core and Shell, LEED O+M: Existing Buildings

Rating System Version

v2 - LEED 2.2, v2 - Schools 2007, v2 - LEED 2.0, v2 - LEED 2.0, v3 - LEED 2008

Inquiry

Our project is a multi-story residential building in New York City. The residential units all comply with the New York City Building Code (NYC Code) as naturally ventilated. Bathrooms require 50 CFM continuous exhaust, and therefore exceed ASHRAE 62.1-2004 requirements. The ventilation design is described below: >NATURALLY VENTILATED AREAS: NYC Code requires operable roof or wall openings with a minimum openable area of 5% of the net occupiable floor area, a 25 % increase above ASHRAE 62.1-2004. Kitchens, defined as greater than 80 SF by NYC Code, must be naturally ventilated and therefore all have access to operable openings. Kitchenettes, defined as less than 80 SF by NYC Code, can provide continuous exhaust ventilation at 2 CFM/SF in lieu of natural ventilation. However, NYC Code does not restrict naturally ventilated areas to within 8m (25 FT) from operable openings and therefore several of the units contain small areas (between 50-200 SF) beyond 8 m (25 FT). By law every unit exceeds the ASHRAE-required ratio of operable openings to occupiable floor area by a minimum of 25%, and in application often far exceed the legal requirement. QUESTION 1: Since the entire residential unit is approved as naturally ventilated "by the authority having jurisdiction" can the entire residential unit considered naturally ventilated for this prerequisite and is therefore exempt from the 8 m (25 FT) limit imposed by ASHRAE 62.1 2004 Section 5.1.1 consistent with the "Exception to 5.1" regarding "engineered systems" and LEED-NC CIR ruling from 1/13/2009? QUESTION 2: If not exempt, can the project comply with EQp1 under the approach for "engineered natural ventilation system" by mechanically inducing more than 0.35 ACH in all occupiable areas located more than 8m (25 FT) from operable openings? The engineered system will include: > A minimum 25% increase above ASHRAE 62.1-2004 in fresh air provided through operable openings (as described above). > Continuous bathroom exhaust fans, continuous exhaust at all kitchenettes without natural ventilation, and continuous dryer exhaust with variable speed CFM (based on building-wide pressure sensor readings). Makeup air to the exhausted areas is provided by adjacent naturally ventilated spaces via infiltration and natural ventilation, per the assumptions of Table E-2. > The total exhaust CFM provided for each residential unit is more than 15 CFM per occupant and is also substantially more than 0.35 air changes per hour (ACH) for areas greater than 8 m (25 FT) as required in Table E-2 for residential living areas. > All occupiable spaces greater than 8m (25 FT) of operable openings would a) be located between the operable openings and exhaust fans, or b) have transfer grills connecting the spaces to the room containing the exhaust fan to induce airflow. In no case does the area greater than 25 FT from operable openings require more than 10 CFM to induce 0.35 ACH.