Cold air return flex duct in attic


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Old 09-07-22, 04:52 AM
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Cold air return flex duct in attic

I am planning to put a cold air return in a 2nd floor bedroom. The shortest path to a return box/branch is through the attic as in the pictures. This does not require cutting any top or sill plates in the walls. Point 1 is the bedroom wall, point 2 is where the access to a big return box is. I am planning to use 6" flex duct. The distance between the two points as shown is about 8'. The house is in Chicago suburbs.

Will there be any problems if I just lay the duct on top the attic floor insulation as shown in the pictures?
Thanks in advance.



 
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Old 09-07-22, 08:17 AM
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Supply or return, being in an attic you should be using insulated material!
 
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Old 09-07-22, 09:31 AM
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You can lay the duct on the attic floor or you can support it from above with nylon duct strapping.
 
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Old 09-07-22, 11:04 AM
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Marq1. I think my options are insulated flex duct or metal duct wrapped in a duct sleeve, right?

Pilot Dane. I read online that flex duct must be stretched tight. Does this mean it's cut it a bit short and stretched when attaching to takeoff and boot?
 
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Old 09-07-22, 11:32 AM
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Since it's shipped compressed you want to fully straighten out the flex duct. This will help get rid of folds inside that can restrict airflow or trap moisture. Do not install it under tension since that can cause it to eventually pull free. So... somewhere in between. I give it a pull (grab everything so you pull on both on the inner and outer portions) to make sure the inner lining is straightened then install it so it does have a bit of extra length but not enough that it can kink or sag excessively.
 
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Old 11-13-22, 01:10 PM
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I completed the project as shown in the pictures. No issues. Thank you for your advice.
 
 

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