I have small 6'x3'6" room where my furnace (gas) and water heater are, this is located in my family room and its very loud. Can I put solid doors in place of the louver doors? I know I would have to vent but will 2-12" vents above doors and 1-12' vent on the bottom be sufficient? my goal is to reduce the noise. any thoughts? tried calling the county building dept (chicago) but they are no help.

I'm an licensed HVAC contractor in the Southeast, so I can only tell you what would be required here, although it is probably a safe assumption Chicago utilizes the Standard Gas Code or some variation of it.

According to the Gas Code, your room would fall under "All air from inside the building" (304.10 of the Gas Code). This requires you to install two openings, one within 12" of the top of the room and one within 12" of the bottom of the room. These openings need to be sized for 1 square inch (minimum) free area for every 1000 Btuh of the total input rating of all gas utilizing equipment in the confined space, but not less than 100 square inches.

You can safely figure about 40% free area for most "stamped" type residential grilles you find at your local home improvement stores, but I wouldn't go much over that. A commercial type grille will give you a litte more free area, but you would probably not be able to acquire it unless you go through a contractor.

This should reduce your noise problem but not totally eliminate it. Sorry to say, it's just a bad location for the equipment.

FWIW

This may not be practical in a tight space in an already finished house, but I have seen several homes built with two separate air ducts from the attic down to the furnace room. One pipe opening within 12" of the ceiling, one within 12" of the floor inside the furnace room. Ducts are normally about 6-8" diameter round metal(see sizing reference in previous posting). Top ends of the pipe terminate in the attic well above insulation. You could then install a solid door in the basement.

What abimark said is right with one correction. If the attic is ventilated (I assume this to be the case) your sizing criteria changes to your benefit. You can now size your combustion air based upon 1 square inch of free area per 4000 Btuh of total input rating of all the equipment in the confined space in lieu of the 1000 Btuh as previously mentioned.

Hope this helps

Thanks for the advice. I don't have an attic. I think I will go with the solid doors and vents, any reduction in the noise will be an improvment.