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Whether to use Flexible Duct work or Aluminum Duct work for heating?

 Hi, my house is old and does not have Any duct work.  I've been told I could use the Insulated Flexible Duct work and of course some say to use the Aluminum Duct work.  My question is - is there any reason I couldn't use the Insulated flexible duct work?  I'm looking for the cheapest & easiest to do.  I live in northern MN so is gets very cold.  But the way it is right now I'm not getting much bang for my buck with no duct work.  I use LP and use fan's to blow the heat from room to room.  The house one that you can walk through it in a circle.  I'd appreciate any input.  Thanks in advance, msesp  

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Posted 2011-11-20T14:02:15+0000  by msesp msesp

Hi msep I would think the insulated ducting would be the better.  Since you're dealing with pretty cold temperatures the insulated ducting would help prevent heat loss as air travels through the duct work.


Before you dive into the project though I would check with your local codes to see if there were any provisions preventing use of one type over the other.  This will make sure that you do the project once and right and don't have to worry about any major problems down the line.


I'll make sure SteelToes takes a look at this and adds any input he might have.  I have also included a couple videos below that run through some ductwork tips.  


Ductwork Planning


Ductwork install


I hope this helps and best of luck.




Posted 2011-11-20T15:21:44+0000  by Chris_HD_ATL

hello msep,

there are a few things that need to be considered.for instance where will the duct be running through(basement,crawlspace,attic)?if its runnning through an area that is subject to coulder temps you are definantly going to want insulated. if its running through a temp controlled room such as a finished basement its not neccesary to have insulation but it will still help maintain the heat in the duct to get it to the rooms you want it in. if its in a crawl space  under the house or trailer you will eather want to make sure rodents cant get to it and destroy it or go with galvinized and wrap it with insulation. hope this helps. make sure you check local codes .

Posted 2011-11-22T13:42:53+0000  by handymaniac

Hello msep,


My name is George and I have been asked to chime in with some thoughts on this project.


Msep I’m not an HVAC technician and the input provided in this post it’s solely from my hands on experience and research I’ve done in effort to understand this type of work and best practices. New system layout and installation should be managed by an experienced and licensed HVAC technician.


So no ductwork huh  :smileysurprised: ...Where should we start first … ?:smileyvery-happy:


Let’s start with an answer to your question first and then if you’d like you can read the bonus stuff.


Your question was; “Is there any reason I couldn't use the Insulated flexible duct work”?


Possibly YES, insulated ductwork is designed to be used in areas that are outside of the conditioned space. In other words, if the ductwork is passing thru an area(s) that can adversely affect the temperature of the distributed air than that same ductwork should be insulated from that area to prevent temperature loss and condensation.


Perfect example its ductwork installation in attic areas.

It is common for the attic areas in summer months to reach temperatures as high as 150F from the sun shining one the roof deck and for example if you were to install  non insulated ductwork to distribute the air thru that same attic as you can imagine would experience some significant cooling loss and condensation.


From my knowledge it is not required for the ductwork that is placed inside the conditioned place to be insulated. Any heat loss that is present it is still getting distributed inside the conditioned space making it unnecessary to be insulated.


Now reasons not to use this type of pipe throughout the whole house are the size of the pipe (diameter) and locations this pipe would need to be routed to. Because it’s insulated this pipe has a larger diameter that un-insulated pipe and depending on the layout of your home and construction of the walls  and ceilings you may not be able to use this pipe in some sections where it needs to be routed thru the narrow cavities.


O.K I’m going to stop here before it gets confusing and talk about different types of air handling setups that can be used in your home.


Depending on the floor layout, location of the mechanicals and style of your home different furnaces and furnace air handling setups can be selected.


For example for homes that are build on grade and have neither basements nor crawlspaces and are limited with square footage horizontal furnaces can be installed inside the attic areas .If this is what your setup sounds like than you would most likely use insulated ductwork for most of the project. With the horizontal units that are installed in attic areas waterproof pan need to be installed underneath the unit and drain outlet provided.


If your home layout and mechanicals call for the furnace  to be placed on the first level or in the basement  than you would go with the upflow unit and your main ductwork - “trunk line” would be running above the unit up against the ceiling with “take offs” placed in between joist branching off in desired directions.


And finally in a mobile home or home with the crawlspace down flow unit can be installed. Main trunk line and ductwork for this type of installation its bellow the floor and if the crawlspace its unconditioned ductwork would need to be insulated. Now this is the least favorable installation, units that are placed in crawlspaces are exposed to  moisture and water penetrations.


Now you mentioned you are using fans to blow heat from room to room which makes met think you have an old conventional system installed ?Before development of forced systems  gravity furnaces were used.

These furnaces had to be located centrally with short runs of ductwork. And if this is what you have keep in mind that these units do not have a capability of forcing air to different sections of your home.


Hope this helps and good luck with your project.



Posted 2011-11-22T19:08:39+0000  by George_HD_CHI
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