G2407.5.1

Section G2407.5.1 is titled 'Standard Method' and covers the requirement for providing indoor combustion air where the air infiltration rate of the dwelling is unknown. The required volume of space must be 50 cubic feet per 1000 Btu/hour input appliance rating.

The model shows an enclosed room which contains a natural gas furnace which has an input rating of 65,000 Btu/hour. This equates to a required 3,250 cubic feet of room space. Presuming the ceiling is 8' high, the room would need to be 406.25 sq. ft., which is slightly larger than 20' x 20'.