flexable ducts?


  #1  
Old 12-01-05, 05:07 AM
Sam
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flexable ducts?

I am finishing off a second floor addition and am putting a heating / cooling system in the attic for it. I have purchased flexable ducting for the project and am ready to start installing. I have now been told by a friend that I should not use the flexable ducting that the air flow loss is too great and I will not get enough air. My shortest run is about 8 feet and the longest is 18 feet. Is there a problem with using the flexable duct?
 
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Old 12-01-05, 06:27 AM
N
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Flex Duct

Originally Posted by Sam
I am finishing off a second floor addition and am putting a heating / cooling system in the attic for it. I have purchased flexable ducting for the project and am ready to start installing. I have now been told by a friend that I should not use the flexable ducting that the air flow loss is too great and I will not get enough air. My shortest run is about 8 feet and the longest is 18 feet. Is there a problem with using the flexable duct?
First I want to make it clear that I'm not a contractor, moderator or expert on the matter. I will respond from personal and practical experience I have had over the years with my own home as well as some rental houses.

Flex duct is being used more and more because unlike metal ductwork, it's much cheaper and easier to install. Flex duct consists of spiraling ridges which collects the recycled dust and dirt being re-circulated through the forced air ductwork system. Flex duct also has a tendency to sag and hamper the air flow which causes the furnace and airconditioner to work harder to force or push the air through the ductwork system. Even if flexduct doesn't sag, it still causes more resistance to air flow than smooth metal duct work. Consequently heating and airconditioning bills are higher.

Were flexduct not so popular and widely used these days, it would probably be banned.

As I mentioned, I'm no HVAC man and don't have the charts and computations, but just as a practical and logical observation, I would say that if your longest run of flexduct is going to be only about 18 feet, it shouldn't make a significant difference. If a home has flexduct throughout -- now that does indeed make a difference.

The above is just my practical opinion. Wait for some more answers from qualified people on this forum.

Regards
 
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Old 12-01-05, 06:44 AM
E
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IMO, flex duct should be banned. It has absolutely no practical purpose.

In a dryer vent situation, it has been proven to be a cause of household fires.

In a bathroom vent, it has been proven to collect moisture in between the ridges which can lead to mold.

In an HVAC system, it has been proven to dramatically reduce air flow which requires your furnace to run inefficiently.
 
 

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