Scott H., For the spaces that are cooled, wouldn't the following highlighted section apply regardless of whether the conditioned space is 20,000 SF or not? This would mean that you would essentially be breaking up the building into two parts: 1. Non-mechanical cooling (System type 10/11) 2. Mechanical cooling (System 3 or 4) - assuming that the cooled space is less than 25,000 SF [cid:image002.png at 01CD8A77.7EA1D9D0] Maybe I misinterpreted your email, but is seems that this situation of some mechanically cooled space in a predominately non-mechanically cooled space is taken care of by G3.1.1 item f (highlighted above) that was added with addendum dn to 90.1-2007 - no exceptions or minimum square footage is required. Regards, Scott P.