# Questions on replacing 20yr old flex duct



## Back40 (Jul 20, 2015)

I need to replace the flex duct in my crawl space and looking for any helpful info I can get. What R value? The more the better? When to use foil tape vs mastic? Should I replace the insulation wrapped around the plenum? Thanks for your feedback!


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## buffalo (Jul 20, 2015)

First off , why are you replacing it?


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## Back40 (Jul 21, 2015)

buffalo said:


> First off , why are you replacing it?



The original flex duct insulation has split in many of the sections and some are actually leaking.


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## buffalo (Jul 21, 2015)

Hard pipe would be better for airflow,  typically 6" round is used wether flex or pipe , you would need to confirm the size. If hard pipe is used they sell insulation that slips over it. 

Insulation to cover plenuim

Insulation tape , I couldn't find a link with the tape with fibers. Here we used a foil tape that has fibers , you need siccors.

6 " duct flex .


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## buffalo (Jul 21, 2015)

We use what I call panduit straps , real big zip ties , for attaching flex. There is a tool that tightens and cuts them . 

As far as sealer , we don't seal flex , you reply on the panduit strap to seal. Google ductwork sealant if you need to connect hard pipe.


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## frodo (Jul 28, 2015)

all boils down to your choice.

flex duct or hard duct.

after you make up your mindl  i can help with how to install'

i am not going to type out how for both, 

flex is cheap...as you can see,you will repalce latter down the rd

hard duct cost more, but is their for a longer time


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## frodo (Jul 28, 2015)

http://fairhavenservices.co.uk/wp-content/uploads/2013/11/Duct-Wrap-1_large.jpg


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