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Ducting Question

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  • Ducting Question

    Hey guys. I have a 100,000BTU forced-air-furnace in my shop. It is located in the "woodworking/heated" side of the shop. I have a 2x6 wall separating that section from the "machine-side". I'd like to make a "box" (plenum) so I can divert heat from the woodshop to the machine shop (temporarily) for when I'm working out there. It's typically unheated. I would have to divert airflow through the wall. The outlet is 20"x16". I'm wondering if I can just build a wooden plenum from MDF and hardboard in the shape of a square. Typically I would leave the "box" open on the wood-shop side. Occasionally, I would pull the back panel and leave the "machine-shop" side open (closing the woodshop side.

    Can I construct this with these materials, or do I have to use metal? (I'm good with wood/not with metal)

    Will it hurt airflow too much to construct this in the shape of a "box" rather than diverting the air at a 45 deg angle?



  • #2
    Re: Ducting Question

    First off, dont use wood as a plenum or duct source on a Gas furnace, sorry, but thats just asking for it down the road.

    there are many factors regarding the size of the plenum, mainly CFM/air volume.

    Without knowing that, its hard to say what size plenum you would need as well as the branch ducting required.

    Back to the issue of wood, I would be hard pressed to think the wood idea would be more economical to build. Contact a local HVAC Contractor, (Commercial that has a duct fabrication shop) and get a price from them, you might be suprised how cheap it will be.



    • #3
      Re: Ducting Question

      why don't you just cut a hole in the wall and put a small vent fan (maybe a cheap Attic ventilator )in and just blow some warm air from one room to the other? put it near the ceiling because hot air rises.

      is that one of those heaters that you see in most garage shops that has a grill on the front or is it like a regular one that would be in your house just with no duct on it? if it is like a house one you could get some duct board (it's made of fiberglass) if its not like a house one don't try connecting to it.
      i agree with biscuit on the wood thing.
      Last edited by jaminjimlp; 11-20-2007, 11:07 PM.
      ROMANS 10:9 confess with your mouth that JESUS is LORD and believe in your heart that GOD raised him from the dead and you will be Saved.


      • #4
        Re: Ducting Question

        Thanks guys. I'll check local costs for both!


        • #5
          Re: Ducting Question

          National Mechanical Code. You must construct all supply ductwork from metal or a listed fire-rated material (ductboard) Under no circumstances can you use wood here. If the place burns down and the insurance co. finds out you used combustable materials here I doubt they would pay off the claim.


          • #6
            Re: Ducting Question

            Got it, Thanks. I won't be using wood.