Move duct work from foundation to attic


Old 01-30-03, 05:01 PM
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Question Move duct work from foundation to attic

Recently purchased a home with Down Draft Hot Air Furnace. Furnace is in great shape. However, the duct work under the house is rusted, therefore I am going to by an updraft furnace in the future. However, currently, money is low, and since I need to put duct work in the attic for the future. I would like to put the duct in now and re-route the current airflow up into the attic.
House is 2700 sq foot 4 bedroom ranch (total of 10 rms), and the furnace is a trane (unkown model). How much air flow will I lose re-directing the air into the attic, what size pipes should I use too the attic and throughout the attic?


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Old 01-30-03, 05:04 PM
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Putting in new duct

Please see my previous post "Move duct work from foundation to attic." Instead of replacing the furnace or putting duct work in attic, it was proposed that I should use the old duct work as a conduit and pull smaller flex hose through the duct and make a new plenum and vent boxes (I am not sure how I will fix the plenum that is under the foundation, un-accessible). Any thoughts on this idea?


Old 01-30-03, 08:59 PM
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I am assuming the ductwork that is in the floor is metal duct that is in poured concrete.

It sounds like your best option is to replace the ductwork like you originally planned.
The flex duct that you will try to pull through the existing rusted metal duct will have to be considerably smaller to be able to be pulled. This will likely cause a dramatic decrease in airflow and increase in noise.
Also when you try and pull the flex duct it likely will tear on metal projections and screws.
The moisture conditions that lead to the rusting will still be there and would be a problem as well.

You could connect the existing furnace to an overhead ducting system without any losses, but the ductwork to do this would take an incredible amount of room.

Your best bet would be to just leave everything the way it is untill you can do it all together.

You don't tell us what kind of furnace it is.
It would be a longshot, but some furnaces are convertible.

Post the model number.
Old 01-31-03, 01:44 PM
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Just for kicks. How sound or the ducts you have in the floor. I take it you dont need much AC there. So what if you set a new upflow furnace over the old plenum and use it for the return from all over the home and put new duct work up there in the attic made out of FG ductboard and flex.I hope for a 2700sq' home this furnace is near the center of the home. Have done this and it helps keep the floor warm and worked fine ED

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