Basement shop combustion air furnace

[Matthew Eason]

Attached is the space I will have in a new home purchase for my woodshop. Everything will be cleared out, including the fridge and washer/dryer. My first hurdle that I'm trying to figure out is how to seal the space off. Behind the door there are two louvered vents to the living area. For noise and dust reasons I don't want those there. The inspector said they're for providing combustion air to the furnace/gas water heater.

Where I'm standing is an adjacent 'room' eventually to be turned into a bedroom. What you can't see is next to the furnace is a little crawl space closet under the stairs. What are some options for me from those who are in the know?

[Bill Dufour]

Is there an outside wall or window that could be vented.

[Jack Frederick]

Check this out.
https://tjernlund.com/combustionairintake.htm
It will tie into the furnace and runs only on a call for heat. Outdoor louvers just dump cold air into the space.

[sean meltvedt]

If you have an outside wall above grade-this is how we do it up north

[Matthew Eason]

It is a ground level walk out. If I introduce outside combustion air do I then have to deal with humidity?

[Bill Dufour]

I noticed in that diagram if it is a three car garage, or bigger, there is no requirement for any makeup air vent. I guess they figure three garage doors will leak enough air to be safe.
Bill D

[Lee Schierer]

You should be able to provide combustion air to the furnace with some PVC pipe. You may need to check with an HVAC contractor to determine how much air it needs for choosing the correct pipe size. Most high efficiency furnaces use PVC pipe for combustion air. Older systems did rely on air from the room and leaks from the house to provide air to the burner. As a short term cheap fix, install a couple of furnace filters over the vents and an stop the dust migration. Stopping sound is a bit harder.

[Matthew Eason]

You should be able to provide combustion air to the furnace with some PVC pipe. You may need to check with an HVAC contractor to determine how much air it needs for choosing the correct pipe size. Most high efficiency furnaces use PVC pipe for combustion air. Older systems did rely on air from the room and leaks from the house to provide air to the burner. As a short term cheap fix, install a couple of furnace filters over the vents and an stop the dust migration. Stopping sound is a bit harder.

That's the exact same response my dad gave when I talked to him yesterday. Smart guys. I'm going to do the filter thing for now. The tools are going to be loud whether or not there's a vent in the drywall.

[Jack Frederick]

NFPA 54, 2012 Edition, National Fuel Gas Code says that if you are communicating directly through an outside wall with only one opening it must be 12" below the ceiling and have 1 sq in/3000 btu of input of FREE air space. If you have a high and low, it allows 1 sq in/4000 btu input for each. If your furnace is 75 kbtu and using one single you need 25 sq inches of grill. Oops, pardon me, that is 25 sq in of free space. Metal grill manuf will show that spec in their catalogs. If you build a wooden grill you have to figure it out, but a let's say a 4X10 grill with 60% free space means you are netting only about 24 sq in. Using 4" round pvc will net you about 12 sq ". You cannot look at you non condensing furnaces needs the same as those of the condensing furnace. The non-condensing needs a lot of excess air for dilution and combustion air. The think about the grilles through the wall is that they spill continuously. I have been out on so many calls over the years where the inlets grilles are taped up.

[Myk Rian]

I have an 8" skuttle feeding OA to the return duct. It keeps the house pressure from going negative.