# What Are Your Flex Duct Installation Tips



## sillywilly (May 17, 2010)

I am going to be installing insulated flex duct in the unfinished basement (replacing the original rigid aluminum duct that was placed when house finished) for the purpose of soundproofing. I will be starting with the bedrooms and working out all the installation kinks before I move on to the most important part - the Theater Room.

What tips, tricks, do's and don'ts should I know about for installing the insulated flex duct? Is there a recommended place to get it or even a place to NOT get it? Any particular features needed?


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## bpape (Sep 14, 2006)

Just understand that flex instead of rigid tin is going to help with the tin propagating and somewhat amplifying sound going through the house. That said, it's not going to act as a sound barrier. If any of that duct is going to be going into and out of your theater room, it will need to be encased in an MDF box - preferably for at least 15' or until it leaves the room (whichever is longer) and have at least a couple of bends in it.

Bryan


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## sillywilly (May 17, 2010)

Bryan:

Thank you for the tips. I am looking forward to getting the rooms done in the next few weeks so I can move on to the theater and game room!

Is there any special place to get insulated flex duct over another?


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## ALMFamily (Oct 19, 2011)

No, there really is not. I picked mine up at a big box place (Menards) and it worked just fine.


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## bamabum (Dec 7, 2012)

silly willy,

one does not simply get "the rooms done in the next few weeks"

this must be a long dark road with many forks to test your resolve


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## sillywilly (May 17, 2010)

ALMFamily said:


> No, there really is not. I picked mine up at a big box place (Menards) and it worked just fine.



Thanks! That will make it so much faster instead of ordering something and having to wait, pay shipping, etc.


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## sillywilly (May 17, 2010)

bamabum said:


> silly willy,
> 
> one does not simply get "the rooms done in the next few weeks"
> 
> this must be a long dark road with many forks to test your resolve



Gotta love BamaBum - He's quite the motivational speaker!  hehehe

I will certainly let you know when I start posting my build plans and also start my build (refer back to comment about "rooms done in next few weeks" for timeline  )so I can enjoy your encouragement along the Long .... Dark ... Road :bigsmile:


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## tonyvdb (Sep 5, 2007)

Just a warning, using flex duct will reduce the amount of airflow that reaches the rooms by a significant amount due to the uneven surface of the ducts so dont get to carried away.


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## LaserDisk (Nov 21, 2010)

My whole home is flex ducts, no choice. After building my home theater 12x18 room, although I thought I designed it right, the room just wasn't getting enough air. What I had to do and you might consider it now, is to make the home theater room a separate zone. That solved the problem and I now can control the HT room separately and its works great.


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## ALMFamily (Oct 19, 2011)

LaserDisk said:


> My whole home is flex ducts, no choice. After building my home theater 12x18 room, although I thought I designed it right, the room just wasn't getting enough air. What I had to do and you might consider it now, is to make the home theater room a separate zone. That solved the problem and I now can control the HT room separately and its works great.


That works well in warmer climates I agree. However, if you are in a colder climate, most central air compressors are not rated to run in the winter so you really cannot get cool into the room. That was the main reason I looked at a ductless mini split system for my room.


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## LaserDisk (Nov 21, 2010)

Sorry, I didn't even look to see that you are way up there in the frozen north :wave: We have a 2 ton Mitsubishi mini-split in our Florida room/Lanai. Probably the best thing we've done for that room, it really works well. The Mit's has some of the best spec's out there. In my HT with a 60" plasma, 4 power amps, etc., it was really getting unbearable. I wish in hinesight I would have put in larger ducts. In a closed in room like a home theater using a mini-split, I don't know if you would have to install return ducts or not to get the hot air out. Good luck - I love your room.


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## sillywilly (May 17, 2010)

LaserDisk said:


> My whole home is flex ducts, no choice. After building my home theater 12x18 room, although I thought I designed it right, the room just wasn't getting enough air. What I had to do and you might consider it now, is to make the home theater room a separate zone. That solved the problem and I now can control the HT room separately and its works great.


How labor-intensive is it to make the HT a separate zone if there is already all of the HVAC in for upstairs and they placed all of the runs in the basement when the house was completed (basic framing done to basement, HVAC with rigid duct is extent of what they did)?


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## ALMFamily (Oct 19, 2011)

Not sure where you are located so the pricing could be different, but when I had an HVAC guy come out to talk about my options, he quoted me somewhere around $3-4k to run a separate line to the HT. And, it could not be run in the winter unless I got a new unit rated to do that.

That was why I started looking at ductless mini split systems.


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## MrAngles (May 1, 2012)

On my furnace I already had all four sides of the furnace used up for ducting, one for return air, one for 3rd floor, one for one side of the basement and main level, and one for the other side of the basement and main level. Because of that, the only way to put the basement on a separate zone would have been to install dampers on each of the fifteen individual runs that come off of the main trunks, which would have been a ton of money for parts and labor (each of the dampers is a couple hundred bucks), plus highly inefficient due to the dampers being so far away from the furnace itself.

If you have a free side of your furnace for an entirely new trunk, it could be easier/cheaper than it would have been for me.

If you only have a single stage furnace it only puts out a set amount of air no matter if it's heating one zone or three, so the problem with multiple zones is if you're putting air out of just five ducts for the basement vs fifteen for the basement and the main level, the furnace can get overloaded and break. If you have a larger basement, with close to as many vents as the main level, it would work better, but you definitely wouldn't want a zone dedicated just to the theater with a single stage furnace because you would never want to heat that room by itself.

So I went with leaving my basement on the same zone as the main level, and will close the dampers on the vents in the theater if it ever gets too cold or hot in there. I also plan to get a remote controlled thermostat so I can leave the thermostat on the main level, but I can turn the heat on or off from the theater. It's not perfect, but it beats upgrading my perfectly good furnace that was installed less than a year ago, and definitely beats an expensive and potentially less reliable zone solution on a single stage furnace.

Also, The fact that I moved all my trunks to outside the theater room allows me to upgrade the zoning if at some point down the line I do end up getting a two-stage furnace.


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## LaserDisk (Nov 21, 2010)

I was charged $2900 for a 2 ton 19 S.E.E.R heat pump mini-split w/electrical that we had installed in our Florida room. For the home theater, all the ducting was in, but the ducting in the attic was a total mess from 2 separate additions to the house. I was charged $2678 for the added zone, the controls, bypass, and damper. However, $600 of that was too redo the original mess. They put in new plenums, cleaned up long runs, and did repairs. Yes it's a lot of money, but by doing it right the first time, it will make you happy and probably save you in the long run. They installed a digital thermostat that I can set temp, days, hours, etc., love it. They did have to come back out a re-adjust the pendulum, I was getting way too much air. In my case I have a 4 1/2 ton air conditioner for my home. If not adjusted right that's a lot of air if only the home theater room A/C is on. I probably should add that my home is all one level (Florida) 2734 sq ft.


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