I need some help determining the adequacy of a combustion air source. The applicable code would be the 2003 IRC. A gas burning water heater and furnace with combined BTU's of 110,000 located in a confined space accessible only through the garage. There were two combustion air sources noted, both located at the bottom of the space. One air source was a metal louvered grill measuring 14"x6" located in the wood platform the units were sitting on leading to the hallway in the residence. The other air source was a 4" diameter metal pipe dropping down from the attic space and terminating at the bottom of the confined space. I questioned the adequacy and setup of the combustion air sources. The builder keeps stating that the residence was given a certificate of occupancy so everything meets the code requirements rather than actually opening a code book and investigating. This builder aslo tried to tell me that an air gap is not needed at the water heater TPR valve extension so my confidence in his opinion is limited. Thanks for any help you guys can give me.