Question on Swapping Hard duct for Flex Duct

[Goodgutgonebad]

All:

I live in Dallas Texas. I have hard duct that was installed in the home built in the mid 1980s. I believe the ducts leaks and needs to be sealed.

Question: Is it cheaper to replace the hard ducts with Flexible ducts or just get the hard ducts sealed?

[Moose]

If the ducts are accessible, then seal them if you know they leak. Flex duct has more resistance, needs to be larger, may not fit framing.

[dash]

For the hard ducts to be sealed, the insulation needs to be removed,so the metal joints can be sealed.

Hard to say if replacing with flex is less or not,depends on your market.

Alternative is to have them sealed from the inside ,like Fix-O-Flat for a tire.


www.aeroseal.com

[neophytes serendipity]

If the ducts are accessible, then seal them if you know they leak. Flex duct has more resistance, needs to be larger, may not fit framing.

+1

Tear off insulation, fix airflow problems, seal joints with mastic tape, reinsulate.

[openclasspro]

If the ducts are accessible, then seal them if you know they leak. Flex duct has more resistance, needs to be larger, may not fit framing.

110 cfm vs 85 cfm on 6" @ .1 sp:patriot:

[glennac]

Replacement flex ducts for round ducts. 8" for 6", 10" for 8", etc. Basically for the same frinciton loss for the same CFM you need to go up two sizes. This is shown on a flex duct ductulator when compared to a standard ductulator.

[Goodgutgonebad]

I think I'm going to seal the duct work myself. I will remove the insulation and ise mastic on all seems and then replace the filthy/worn insulation with new thicker insulation.

Hopefully I won't screw this up.

[Shophound]

I think I'm going to seal the duct work myself. I will remove the insulation and ise mastic on all seems and then replace the filthy/worn insulation with new thicker insulation.

Hopefully I won't screw this up.

Now is the time of year to do this job. I've done the very thing you're proposing to do...you don't want to do it in a hot attic. Cold, sunny days are not bad up there...anything warmer and you'll want to limit your time in the attic.

Be careful about where you step, also!

And re: flex vs. hard metal ducting...it is hard to find someone in DFW who can install flex duct properly. With the low amount of respect the material receives from the average Metroplex installer, you're better off retaining your metal ducts and sealing them. If your metal ducts currently have the white vinyl jacket insulation wrapped around them, I would recommend replacing that with the mylar jacket duct wrap, and be sure the R value of the new wrap is at least R8. Between sealing the metal ductwork and new wrap, you should see a performance boost from your system, year round.

It's not an easy job. My main piece of advice is if you're going to do this yourself, be as thorough as you can be in your sealing and insulating efforts. Don't forget to remove the vent grills down below in the house and seal between the sheetmetal and the drywall. The worst leak spots in duct runs are wherever a straight run of duct makes a connection to a plenum, a fitting, or to another section of duct.