The City of Austin City Hall project is located in Austin Texas. The climate is predominantly warm and humid. Complying with EQ Credit 3.2 (2 week flush out) requires that the outside air be conditioned, otherwise the building will be contaminated with water that will cause mold growth. We are seeking clarification of the amount of outside air that must be introduced into the building to comply with EQ Credit 3.2. We would like a definition of "100% Outside Air". 1. Is "100% Outside Air" intended to be the air flow rate calculated according to ASHRAE standard 62-1999 using the Ventilation Rate Procedure? In this case, an air handling unit designed to deliver 10,000 cubic feet per minute (cfm) to the space, comprised of 7,000 cfm return air and 3,000 cfm outside air, would be set to deliver 3,000 cfm of outside air during the 2-week flush out, with the return air damper closed and the outside air damper fully open. OR 2. Is "100% Outside Air" intended to be the air flow rate that represents the full design cooling/heating load. In this case, an air handling unit designed to deliver 10,000 cfm to the space, comprised of 7,000 cfm return air and 3,000 cfm outside air, would be set to deliver 10,000 cfm of outside air during the 2-week flush out, with return air damper closed and outside air damper fully open. In this case the air handling unit would be unable to deliver fully dehumidified/conditioned air because the entering air conditions would exceed the coil ratings.
The term "100% outside air" is defined for this credit as follows. EITHER: 1) As reflected in option #2 of your narrative, supply air is 100% outside air (outside air damper fully open, return air damper closed). OR, 2) to achieve performance equivalence: a) After construction ends and with all interior finishes installed, new filtration media is installed and the building is flushed out by supplying a total air volume of 14,000 ft3 of outdoor air per ft2 of floor area while maintaining an internal temperature of at least 60o F and, where mechanical cooling is operated, relative humidity no higher than 60%. b) The space may only be occupied following delivery of a minimum of 3,500 ft3 of outdoor air per ft2 of floor area to the space. Provide a minimum of 0.30 cfm/ft2 of outside air ventilation to the space for three hours prior to each occupancy and 0.30 cfm/ft2, or the design minimum of outside air ventilation, whichever is greater, during occupancy, for the duration of the flush-out period (until the total of 14,000 ft3/ft2 has been delivered). Applicable internationally.
Related Addenda (Corrections & Interpretations)