This not a particularly elegant solution but it works...

• Create a copy of the Open Studio results measure using the 'x2' button at the bottom of the measures tab
• Open your copy for editing. I use notepad++ but notepad will work
• find the os_lib_reporting file
• do a text search for 'convert' convert calls the function to convert the native SI units in Energy Plus to the alternative (and to my eyes unusual) units in the open studio reports
• substitute the second units term in these statements for the one you prefer. Sometimes you will have the change a variable like 'target units' instead.
• go through the table definition and change the table units display as required. looks like table[:units] = ['', '', '', target_units_volume, 'ach', 'ach', 'ach', 'ach','ach', 'ach']. using 'target_units_volume' here is better than hard-coding like 'ach'

This is easy (and I had never seen Ruby before) but not elegant. You can convert to pretty much any units you wish.

For confidence in the results i ran both versions of the report, cut and paste to excel and verify that the result is correct.