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Old 03-13-2014, 09:36 AM   #1
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What brand of flex duct to use?

Seems like there is a lot of price differences in R8 flex duct, quality also I assume. What are some of the "preferred" brands that you use?



HowardBrown is offline   Reply With Quote
Old 03-15-2014, 09:20 AM   #2
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why not use sheet metal ducts. Flex duct can not be cleaned, can cause high static pressure if not pulled very tight and generally, no matter the quality or insulation, does not last as long as metal.

but if you must must must use flex, read up on how to install it correctly (ie mastic seal the ends, sheet metal screws to attaché the ends, support it so that it does not sag or bend, use sheet metal for all 90 degree bends and make sure to properly upsize the ID for air flow to match your system. also, if you use if for a return, be sure you have enough return grill or you can risk collapsing it.


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Old 03-17-2014, 04:06 PM   #3
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here in houston there is a company called "flex master"... i was planning on using this brands generic HVAC low pressure flex duct for my supply runouts.

I think in general they are all manufactured to meet specific specifications for flammability pressures, sound absorbtion, water resistance etc.

you might want to read up on what classification you will need low high pressure etc, and what features you might want, IE accoustical duct, or perhaps a radiant barrier sleve.
Then maby look at the local places see what they have in stock.

Originally Posted by bobinphx View Post
why not use sheet metal ducts. Flex duct can not be cleaned,

With respect to flex not being cleanable? this is the first ive heard of this honestly.

do you mean cleanable via steaming? like in fire remediation etc where smells are the main concern?

Flex has a PE coating of a substantial thickness from what i remember.

can you please elaborate on why its not cleanable?
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Old 03-17-2014, 08:51 PM   #4
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Builders/installers should keep their installed lengths (runs) short, e.g., less than 15 feet or so and minimize turns. However, many times, excessively long runs are used. The round, metal wire embedded in the inner liner creates a corrigated surface which increases static pressure as air travels away from the furnace/air handler. Static pressure reduces air flow as it travels from the furnace/air handler. Second, when installed, kinks or sags in flex must be avoided or minimzed to avoid restricted air flow. Third, rodents can easily chew through the outer liner, fiberglass insulation and inner liner thus entering the duct work where conditioned air travels and enters the occupied space. Obviously, this creates health issues on a number of levels. Lastly, polyethylene liners can breakdown over time allowing splits and holes to develop compromising the integrity of the duct.
Cleaning flexible duct work must be done carefully to prevent punctures/breaches of the inner liner. Once the inner liner is compromised, fiberglass fibers infiltrate the duct creating potential health hazard to occupants.
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