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

We are designing a 4,000 square foot visitor\'s center for a state park which has 3 full-time staff and an average of approximately 80 visitors per day who spend anywhere from 5 minutes to 1 hour in the building. The building ventilation system is designed for natural ventilation using operable windows and doors. The design complies with the LEED NCv2.2 requirements for location and size of window openings in accordance with ASHRAE Standard 62.1-2004, Section 5.1 and with the International Mechanical Code for naturally ventilated spaces. It includes residential-type air to air heat pumps which condition and supply recirculated air from within the building. There are no supply ducts bringing in outside air, similar to a residential design. Infiltration provides the minimum outside air flow. Exhaust fans have been provided in the bathrooms and in the janitor\'s closet as required by the International Mechanical Code. ASHRAE 62.1 - 2004, section 6.2.8 indicates that "exhaust make-up air may be any combination of outdoor air, recirculation air, or transfer air." The make-up air for the exhaust fans is designed to be by infiltration. It is pulled from the neighboring spaces via a duct (transfer air), which creates negative pressure in those spaces, which causes infiltration (outdoor air). Again, similar to residential design. A EQp1 CIR dated 5/15/2007 regarding a similar situation implied that air transfer through a space meeting all the requirements of natural ventilation did not make that space a "mixed-mode" ventilated space. Therefore, we believe the project should be considered naturally ventilated, and does not have to meet the mechanical requirements of ASHRAE 62.1-2004, Sections 4 through 7. We propose that spaces that are naturally ventilated and have air transferred to exhausted spaces cannot be classified as "mixed-mode." We do not believe that it is the intent of LEED that bathrooms (or other spaces that require mechanical exhaust) have completely independent ventilation and conditioning systems, as this would increase the carbon footprint by requiring additional equipment and added energy costs. Please advise whether you agree that classifying the spaces adjoining the restrooms and the janitors closet as naturally ventilated (even though air is being transferred through for make-up air) is accurate and aligns with all applicable criteria. If not, please explain your reasoning using the applicable standards and describe the design changes necessary to meet the criteria.