Replacing Flex Duct

Need my 27 yr old gray flex duct replaced. Have two quotes. Would like some advice on which company to use.

Small company - came recommended from a friend, didn't leave a paper copy of the quote, quoted R6, very good price. Not leaving a quote and quoting R6 raises some red flags for me. Am I just being too critical? I do like the price.

Large company - left detailed paper copy quote, R8, want to move return registers to top of walls, cost is double the smaller company. Like the detail of the large company but do the returns registers need to be moved? Overkill? The HVAC system has worked good for the 10 yrs I've been in the house. The bills are not too high. 2000 sq ft house.


attic or crawl?

Any warranties?
No quote leads me to be weary.

I would press the larger company to explain why they want to move the return grills up. Could be your existing returns use building cavities, and they want to get you away from that by...
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JJ> The previous homeowner did a DIY job of installing a new furnace usingJJ> a twisted maze of flex duct to make all the supply and return runs inJJ> the basement.


JJ> Several heating contractors have advised us that flex is not intendedJJ> for long runs and that this is the most flex they have everJJ> seen. Also, there are no dampers and in some areas the flex is pinchedJJ> and the insulation tearing.

I don't know about long run usage but pinching will cause decreased air flow (depending on the degree of the obstruction, of course). Additionally, the corrugations in the flex duct causes the air being pushed through to have 'turbalance' (for lack of a better word) ==> it bounces and catches on the sides, slowing down the airflow.

JJ> Couple of questions:JJ> - Is replacing flex with rigid sheet metal duct work generallyJJ> worthwile?

I would say yes, as well as having the proper sized ducts. We had an addition put on a couple...

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Re: Flex Duct Vs. Metal/Insulated

[quote=thom;505753]That's false economy. In the real world tests have shown repeatedly that the savings from installing flex are more than offset with the losses in air flow efficiency. Assuming the buyer has a mortgage, the savings in mortgage payments from flex is less than the additional cost of energy from using flex.

Then there's the lifetime thing and the installation failures thing.[/quot

Do you mean somebody built two houses that were identical, one was run with flex, the other with insulated metal. The energy savings from the metal setup was so great that it paid for itself within ten years? If so, great. I am for energy savings, and want to provide what is best for the customer. But, it's a mighty bold claim to be makin Mr.

I don't dispute that air flow is better through metal pipe, but flex isn't so bad.

The flex should last a...
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CINCINNATI (AP) — An Ohio man and his girlfriend have been charged after police say they restrained, gagged and taped his 4-year-old twin boys to a wall.

WLWT-TV reports James Howell Jr. and his girlfriend Jamie Carver have both been charged with two counts of kidnapping and child endangering. Both Howell and Carver were released on bond after a hearing on Tuesday.

Howell’s children have been placed with a foster family by Hamilton County Job and Family Services.

Police responded to a Cincinnati apartment Sunday afternoon. Investigators say Howell and Carver had bound the children with a belt and shoe laces. Police say the boys had also been gagged with socks and duct taped to a wall in the apartment.

Attorneys for the couple were not available immediately for...

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Questions moved to top in this post as I realized I rambled too long....

(1)But the big question would be: If i was to rewrap, what product to use? Do they make a prefab'd sleeve type? Is is cheaper just to take some R-13 and wrap around? Whats the best proceedure? Run (2) longways and tape a seam lenthwise on both sides? What works best if I decide to rewrap.?

(2)With regard to Flex duct, I am concerned about the poor interior construction I have seen in home depot shelf brand. Lowes carries a black on that looks pretty tough on the outside.. So which brand if Going flex?

You guys both have excellent points. I understand I could more efficiently route my attic with the flex. It just seems like an easy "quikfix".. I did not really give consideration to the issue with the resistance. One part of me wants to immediately dismiss and equate to the auto dealer telling me my gas mileage on my new car sucks because of dirty paint causing air resistance.. But I...

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Ductwork is a branching network of tubes in the walls, floors and ceilings. It takes air from throughout the house and delivers it to the heater/air conditioner, where the air is heated or cooled, then delivers the heated or cooled air back into the living space. Both intake and output of air is important to a balanced, climate-controlled system. To operate efficiently, ducts must be sized to match the heater and air conditioner, and designed so the correct amount of air reaches each room. Typical costs:Replacing aging, leaking or inadequate ductwork typically costs about $35-$55 a linear foot for labor and materials, or $1,000-$5,000 or more for a single-family home, depending on the length and type of ducts used (sheet metal, fiberduct or round flexible ductwork) and local rates. (The linear footage of ductwork varies widely depending on the type of heating and cooling system, when and how it was installed and the layout and construction of the house.) Factors affecting the...
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With a little help you can do your own flexible duct installation. The typical rate for an hvac dealer to do the work would be about $50/hour. By providing the labor, you can save around $1000 on the typical duct system.

**NOTE** Only you can assess your ability to perform this task. This is a guide and cannot provide all of the details for every situation.

You will need some basic tools to perform the job but they are not very expensive.

We will look at installing an extended plenum system in an attic. After you understand the process, the methods can be used for other applications.

The Plan...

The flexible duct installation process begins with a load calculation. This is a computerized process of determining the heat gain/loss for each room in the home. This information is then used to design a properly balanced duct system. The result is a duct layout plan which shows the size and location of the air ducts and registers in...

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There is an abundance of information out there regarding duct sealing; however, when specifying ducts for a new construction project there is not a straightforward solution.

The primary reason for the focus on sealing duct work is energy loss. The EPA Energy Star program estimates that as much as 20% of the air moving through a duct system is lost due to leaks, holes, or improper installation.

Keep the metal ductwork

The lack of information on "which duct product is best" is justified because the short answer is: "it depends."

To properly specify duct work for your home, a mechanical engineer or contractor needs to perform calculations specified in Manual D Residential Duct Systems. This manual is an ANSI-recognized set of instructions for calculating proper duct size for a home.

Having seen the results from a duct blaster on many different configurations of residential duct work, I would recommend keeping the metal duct work and cleaning...

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I've written a lot about duct problems, especially those in flex duct because they're so abundant. A couple of years ago, I even wrote an article about whether or not flex duct should be banned. My answer was no but that we need better quality control. When I updated and reposted the article recently at Green Building Advisor, Jack Lagershausen, the executive director of the Air Diffusion Council, sent me a letter.

Unlike a certain, very large company that threatened me a while back, the Air Diffusion Council was smart about it. He admitted that the problems I wrote about are "far too common" and sent me a complimentary copy of their installation guide, Flexible Duct Performance & Installation Standards. Today, with the hope that some readers will act on this information, I'll give you a bit of an overview of this guide and encourage every HVAC company installing flex duct to invest the $15 and get a copy. Then use it to train your installers.

A few tidbits from the...

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Posted By: airman.1994 I'd run twenty feet of 7 inch hard pipe over two her room then flex from there

airman and Grady, I don’t want to sound ungrateful, because I truly appreciate the time and advice you’ve given me so far, but that advice is causing me more grief, when the fact is, I came here in hopes of relieving at least some of my grief. I also realize that you guys are giving me the best advice with the hard duct recommendation and that my attic and the current set up of my rear A/C system, along with my lack of experience are what is truly causing me the grief, but it is what it is, and I have to deal with that. Thus, I would greatly appreciate a little more information and input from either or both of you, or anyone else for that matter.

First, let me tell you guys that I’ve had numerous A/C contractors in my attic to get some recommendations on how to improve the efficiency of my rear A/C system. Not a single one of them have suggested hard duct, and only a...

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Sure, if you're going to replace a duct anyway, use the highest R-value available. When my house was built 2 years ago, code called for R4.2, and that's what they used. It went up to R8 briefly sometime after Katrina, but then for whatever reason, it got knocked down to R6, where it stands today. I just happened to see a bunch of R6 duct recently at Home Depot and bought one as an experiment. After replacing one R4.2, I didn't observe any difference in the temperature of the air coming out of it; it appeared to gain as much heat as the original. I guess there might have been maybe a couple of tenths of a degree difference, but I don't know if that's going to significantly improve the comfort level in my home. For the time being, at least, I'm focusing on sealing the ductwork, caulking all the gaps around ceiling penetrations, touching up underinsulated spots, etc. I think fixing conditioned air going into the attic and attic air coming into my house has a better...

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I know "estimates" vary by location, but I don't want to be in sticker shock...

anyone have a guess of what it would cost to replace a whole trunk line form the furance?

The branch lines are all insulated flex duct, and would remain in place so that cost is out of the project...

Right now the trunk is 24x8 (undersized for the furnace I have...) its metal...

I wanted to put in 3 new lines one for each zone that will be created... so I'd have a basement zone, 1st floor zone and 2nd floor zone

the current trunk plenum is 50 ft long...

I'd imagin this would be less then $10k for the trunk to be replaced? I'm talking the sheet metal ducts to be fab (it'd all be rectangular)... mastic... the s-channels... the take offs.... (25 takeoffs in total)

I guess I'm just looking for a range so I can say this is costing me to much...

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This website is designed for people:

I have been working as an HVAC installer and later as a mechanical engineer for 34 years and discovered that there no manuals and/or books for this type of work. But I created seven of them that I believe are very good and useful for anyone who wants to learn HVAC installation. was created in August 2006. Since then it has become massive and the most reliable source of information!

Currently it has:

One hundred and two main menu and parent pages
One hundred and fifty paid and download pages, many of which also have additional information Seven helpful books On the, you can find answers to many ductwork, furnace/air handler and related questions, such as noise reduction and elimination, energy conservation, furnace replacement and so on. has 7673 pictures, 69 pdf files, 386...

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