DIY Plenum and Ductwork Replacement

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Also, my plenum is made of what appears to be some material that's not really ridged.

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Every residential plenum ever.

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by poochie Can I just go to coburns and buy panels to build a new one?

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Just buy a new plenum. Take measurements. They come with the sheet metal already cut and hemmed with insulation. You put it together.

But seriously, this is probably a job well beyond your skill level. Call a professional.

My heater went out over the winter. Two different companies came to my house a total of 7 times and couldn't figure out the issue. Per one of them after 4 tries they were "still diagnosing it". I got fed up and googled my modle number (of a now defunct brand) and the issue I was having, figured out the control panel was bad after about 10 min of searching, ordered a new one online, and replaced it. Called both companies and told them to send me credits because ideas not paying my bill for them not doing anything. And they both did.

I think I can handle a little sheet metal work.

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I think I can handle a little sheet metal work.

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Its a lot more difficult than it looks. I'm just trying to warn you. You don't want to get in an attic and get have your ductwork pulled out only to realize you can't get it all back together. Its also not as simple as just re-running flex duct from the plenum to the diffusers. You'll need to see if you've got dampers as well. If you're going with hard pipe, its a lot less forgiving than flex, and a lot more expensive. It'll need to be properly insulated as well.

I'm am the worlds biggest advocate of DIY. But I'm very aware of whats above my head. Just some friendly advice.

Get some insulated plenum board, a box cutter and silver tape, with a little planning you can do as well as 99% of the so called professionals. Every thing you need is online, do a search for "wholesale HVAC", and pick as supplier. Home Depot and Lowes also sell duct and plenum material.

Laying the schedule out in my head: I'd get all the duct as reasonably close to ran as possible (basically ran next to the old duct) and I'd prefab the plenum in the attic next to where it's going to rest. Then once I have everything in place, the next available decent weather weekend, I'll pull all the old stuff, install plenum, connect ducts to defusers and new plenum. No dampers, all straight duct runs with one split. AC cools the house well enough but I know I'm losing a lot of efficiency with leaks. I plan on matching diameters to current ductwork.

Regarding flex vs hard duct, my house is a mishmash of both with original being hard, then two additions being flex. I would like to go all flex with the new stuff. Is there any downside?

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Can I just go to coburns and buy panels to build a new one?

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Betz sheet metal is your friend or someone else in town or use duct board