Anybody know how to make residential ductwork?

[dieselscout80]

How much flow will I lose in 6" duct going with 10' of flex vs metal/pipe for a run?

 

[Stimw]

Once you read the instructions and understand how the seams and joints are cut and assembled Duct Board is dirt dumb simple to work!!
A utility knife will do all the cuts that you need, the tools would be nice to have but if you are handy you can get by. The trick is to be able to cut to the depth for the joints, this can be set by utility blade ajustment.
The board is sold in 4' X 8' IIRC (might be 4' X 10'). The aluminum tape for it is sold where it is AND there is a coating/sealer that goes over the tape (water based) that is not expensive and is easily applied with a paint brush. The sealer helps with poor taping jobs too.
To attach board to metal you just use a sheet metal strip and screw it together clamping the board firmly but not too tight. Then tape and seal.
The pic is of a heat pump that I ran DB out of the top but had to direct the air flow to the bottom making a plenum for it in the process. It was very easy to do.
Oh I almost forgot it's not expensive either!!

 

[buckeyefarmer]

metal trunk duct is readiliy available at most supply houses. If they don't carry the transitions like a reducer, you can make one with a piece of trunk duct. You can look at trunk duct at
Audubonsupply.com
to get a feel for the sizes available. Normally residential uses 8". I have not bought from audubon, I buy from a local supply house. Also Home Depot here has some trunk duct, 24x8 and 16x8 in 4' lengths. You buy 2 pieces per length and hammer them together. The sections then go together with s cleats and drives. Also, a folding tool is useful. I've even made plenums out of duct pieces. Unless you want it to be really pretty, you don't need a brake, bend it over the edge of a piece of wood or table edge, you can square it up some with a hammer if you want. I just made a plenum the other night.


Duct sizing is done with Manual J and Manual D calculations... As the trunk drops off volume, it decreases in size. The cheapest trunking system is with the AH at the Center.

 

[rtimgray]

Thanks again fellas. I'm not sure which direction I'll go, either ductboard or sheetmetal, but I appreciate the advice on both counts. My only problem with ductboard is that I can't find anybody locally that carries it - in fact, none of the supply places that I've called have any idea what it is. I'll expand my search a bit and I'm sure I'll come up with something.

Once again, thanks for the help.

 

[Deere Dude]

Of all the DIY I met in my life, I never heard of anyone wanting to fabricate sheet metal duct-work from scratch. IMHO, if it were for just a house, it wouldn't be worth the headaches involved. Local suppliers have the big brakes and expertise and sell the halves and pound them together and they work nice. I would have to be pretty bored before I would tackle something sheet metal ducts. Good luck and let us know how it turns out.

 

[Dr Dave]

Menards has every thing you need, steel plenumn kits, trunk line panels, filter housings, and the foil covered cardboard return duct panels. Pick up there duct catalog or check on line, it shows complete system lay out and all parts required.

Dave

 

[rtimgray]

Of all the DIY I met in my life, I never heard of anyone wanting to fabricate sheet metal duct-work from scratch. IMHO, if it were for just a house, it wouldn't be worth the headaches involved. Local suppliers have the big brakes and expertise and sell the halves and pound them together and they work nice. I would have to be pretty bored before I would tackle something sheet metal ducts. Good luck and let us know how it turns out.

My desire comes from the desire to save money - the cost that I have paid for fabricated duct in the past is just outrageous. The more I investigate it, the simpler it seems, so I think it's something I'm gonna take on. I always seem to have more time available than I do money. Plus, I do like to learn new skills.

My local suppliers don't return calls or give quotes very readily, so the less I can involve them, the better. That is a pretty big driver for me as well.

Thanks.

 

[rtimgray]

Menards has every thing you need, steel plenumn kits, trunk line panels, filter housings, and the foil covered cardboard return duct panels. Pick up there duct catalog or check on line, it shows complete system lay out and all parts required.

Dave

Now all I need is a Menards close by! I'll check them out online. I think the closest one to me is either is Southern Illinois (maybe Marion) or Evansville, IN. I love their stores and hadn't thought of them. If I can pick up a lot of stuff, it would be worth drive.

Thanks for the thought.

 

[Dennisfly]

You need a design that will be efficient before you fabricate anything. I'm not an expert, but my brother is an HVAC contractor in California. The first step is to do a load analysis to determine the proper size unit and then you need the whole duct system sized to accomodate the unit and proper flow in each zone or room. This will relate to CFM of the air handler, static pressures, the duct type, size in length and width, number of turns, etc. An improperly designed duct system will result in high operating costs, stress on the the compressor for an air conditioner or heat pump if your using one, rooms that are constantly too hot or too cold, and excessive air noise. According to my brother, money spent now for an engineer will be more than returned in future energy costs, durability, and comfort.

I had a house built on the east coast by a contractor and my brother happened to be visiting at the time. My brother looked at the ducting as it was being installed and said it was not designed properly. The general contractor called the HVAC contractor who conceeded that it was not designed and sized right and they ripped out the whole main duct and redid it. The second one they installed was improved, but still not correct so they redid it a third time. If I had to grade it, the first try was an F, the second a D, and the final a C+. This was an HVAC contractor that had been in business for 25 years and, according to the general, had a good reputation.

There is a calculator tool for duct design used in the trade called a "Ductulator". Several companies make them, but according to my brother, Trane is one that is used a lot. My brother said the Ductulator is not for use by the layman. I'd find an engineer that knows how to use a Ductulator.

 

[rtimgray]

Thanks for the information, Dennis. I think I can handle the design of the ductwork pretty well - I've picked up several manuals that go through loading, cfm, etc. They deal with the project in step-by-step fashion and explain why each step is important. One of them is an educational text, some of the others are OEM manuals, but they more or less follow the same process. My opinion on that is that, for a large part, the complexity of the craft is an illusion. As your experience dictates, just because you pay a professional HVAC contractor to do something doesn't mean that it's right. My project is pretty simple and should end up in a straightforward installation.

Thanks for the help.