ASHRAE Standard 62.1 - 2010

George, the breathing zone requirements for 62.1-2010 are similar to 62.1-2007, although a greater number of space types are now provided. I would stick with 62.1-2007, unless you're able to demonstrate compliance with the entirety of 62.1-2010.

He could also try the following. I'm not sure what the ventilation difference between 2010 and 2007. I have a set of 62.1-2007 calculations from an engineer. The engineer used an special software tool called HVAC Comply-VAV from hvacdesignsolutions.com. The tool doesn't have a 2004 version, but there is 2010 version. Rather than make the engineer use a different tool (ASHRAE or LEED Form) I marked up the output to show that the ventilation rates per space in the project matched between 2004 and 2007. In other words the compliance is the same. The Comply-VAV tool includes adjustments for intermittent occupancy use. It shows both calculated and default occupancies so they can be compared. The only thing I this tool, and no tool I am aware of, does not do is calculated heating and cooling OA amounts based on occupancy percentages that would trigger each ventilation mode. Cooling should always be the dominate OA requirement. LEED reviewers will demand that heating calculations be provided, under a false assumption that heating is the dominant OA ventilation mode when a space is at maximum occupancy.