Hello,
I have a Goodman gas furnace that's 90% efficient. I bought the equipment and hired an installer. He didn't put in any fresh air intake. There seems to be an intake opening (about 3 inches with crisscross grating) on the side of the unit near the gas line. The unit passed the rough in inspection, but I'm due for the final. The installer said to put a 4x10 register going into the crawlspace and a 6 inch pipe going to the attic. The unit's on the first floor, but I have a chase going to the attic. Is what the installer suggested a good thing to do? Can I install a smaller line (2 inches) directly to the unit's intake opening, and does this need to come from the roof or the attic? I'm not sure of it's importance, but the room is about 8x10 with 10' ceiling. There's also a gas water heater and dryer in the room, and a door is open to the rest of the house.
thanks, Don

While not always required, direct-venting the combustion intake to the outdoors is recommended, especially if located near other appliances that will "compete" for combustion air. Local building codes ultimately dictate whether the intake vent is required or optional.

I hope you meant "insightful". I don't want to be responsible for starting any riots... :D

The installer said to put a 4x10 register going into the crawlspace and a 6 inch pipe going to the attic.

If the inspector is going to be looking for 50% high and 50% low combustion air then that is what you will have to do. The high efficiency furnace can be piped direct but any other appliance that needs combustion air unless high efficiency and direct piped will have to be taken care of like the installer said. 50% high and 50% low like the code calls for. You will also need to do a exact calculation figured with all appliances running (fuel usage in BTU'S) that will use the combustion air to perform exact calculations for the amount of square inches necessary to do the job.