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

This CIR concerns ventilation design and IAQ performance of a six-story residential building in Nebraska. The unit floor plans will in part require use of mechanical ventilation to fully satisfy ASHRAE 62.1-2004 outdoor air requirements. It is clear the intent of ASHRAE Section 6 is establishment of minimum (mechanical) ventilation rates to enhance indoor air quality. We would like to verify our compliance path is acceptable for LEED certification. Question 1a: We intend to introduce the prescribed outdoor air requirements via 100% outside air type rooftop units. The rooftop units will provide filtered conditioned air for the commons areas and makeup air to the kitchen/toilet exhaust fans along with supplying outdoor ventilation air to the resident units through a ducted supply interconnected to the return air duct of each resident unit\'s condensing type gas-fired furnace. To ensure continuous supply of ventilation air, a whole building energy management control system (EMCS) shall verify that resident unit furnace fans are operating continuously. We believe this approach will ensure a consistent supply (ACH mechanical ventilation rates as prescribed by ASHREA 62.1) of clean (twice-filtered) outdoor air that will enhance indoor air quality. (Regional and local outdoor air quality is compliant.) Will this be an acceptable approach to achieve the required ventilation? Question 1b: To balance the impacts of ventilation rates on energy use, we propose to allow building residents limited access to the EMCS for the purpose of setting occupied/unoccupied schedules (see also provisions of ASHRAE Section 6.2.7). During unoccupied periods, the ventilation fans need not run continuously, thereby conserving energy otherwise consumed conditioning the outside air supply. Regular (ASHRAE prescribed) ventilation air changes would resume at the EMCS-set occupied periods. We believe this feature can preserve the intent of indoor air quality-ventilation for occupant comfort and well being, and be a valuable energy conservation measure. Will this control feature be acceptable to LEED as it relates to ventilation requirements and minimum IAQ performance? Question 2: Clarification of previous CIRs - Kitchens meeting natural ventilation as defined in ASHRAE 62.1-2004. CIR ruling dated 1/7/2008 stipulates "direct exhaust is required to satisfy section 5.8." Section 5.8 discusses combustion air and fuel-burning appliances. Please confirm CIR ruling dated 8/30/2007 ("If the kitchens qualify as naturally ventilated spaces, and there are no special requirements for combustion air or removal of combustion products, then there is no exhaust requirement.") is applicable in the circumstance of electric cooking ranges (thus no combustion air or combustion products). In short, some of our resident unit kitchens have operable windows satisfying Section 5.1 of ASHRAE and we will have electric cooking ranges. Under these conditions, the range hood is not required to be direct vented to the outdoors and a recirculating hood is acceptable? Question 3: We intend to install unvented natural gas fireplaces in the resident living units. These are allowed by our local code. Combustion air supply has been accounted for and will be provided. The fireplaces will be sized and installed in strict accordance with the manufacturer instructions for safe operation. Will use of unvented fireplaces be acceptable to LEED in terms of ventilation requirements and minimum IAQ performance?