Our LEED application is for a high-rise residential building (over 40 stories), located in downtown Los Angeles, with underground parking. The Indoor Environmental Quality prerequisite for minimum IAQ specifies ASHRAE 62-2004 as a requirement, or the most stringent local design guideline. We are concerned with parkade ventilation, as ASHRAE 62-2004 specifies 1.5 CFM/ft2 as a design level for this type of space. The State of California building code has a basic requirement for 14,000 CFM times 2.0% of the total number of stalls (rounded up). We have experience designing parkade structures in Vancouver under the CaGBCs LEED Rating system (version 1.0, 2004). In these cases, we have utilized an alternative compliance path to achieve the minimum IAQ prerequisite 1. This compliance path was to follow the British Columbia Building Code, which on its basis requires 0.75 CFM/ft2, and to implement CO sensors to bring in more outdoor air as required to meet the CO levels as shown in ASHRAE 62-2004, Table 1. This strategy achieves a healthy IAQ level for the space according to ASHRAE, and complies to the local building code. For the parkade spaces of our building, will we meet the intentions of the prerequisite if we comply with the design requirements of the State of California Building Code and implement CO sensors in an identical manner as described above to comply with ASHRAE?
Your proposed method to comply with this prerequisite must comply with ASHRAE Standard 62.1-2004 requirements or the local code, whichever is more stringent. Standard 62-2001, which does not apply to NCv2.2 projects, required 1.5 cfm/ft2 outdoor air) for parking garages and allowed the use of contaminant sensors (e.g., CO sensors) to control outdoor airflow. Standard 62.1-2004, however, requires 0.75 cfm/ft2 (exhaust air) and neither requires nor prohibits the use CO sensors to control exhaust airflow. The methodology you described above meets the requirements of standard 62.1-2004, and the state of California Building Code requirements; therefore the methodology is acceptable.