ductwork

[fishin]

my supply ductwork is all metal except for the last 6 ft of each run which is flex. a/c guy said this makes for a tighter system and the flex baffles air noise and hooks to the supply boots easier. the air noise is more noticeable than other systems that have all flex. is more air noise normal because of so much hard pipe?

[dash]

Yes ,that or the ducts are on the small side ,causing higher velocity air thru them.

[leander311]

Agreed. Static losses on sheet metal ductwork are much less than their flex counterparts, however, which means less fan power used and better efficiency.

[dash]

Originally posted by leander311
Agreed. Static losses on sheet metal ductwork are much less than their flex counterparts, however, which means less fan power used and better efficiency.

Sized corectly ,flex and metal can perform the same,yes, the flex sizes will be larger then the metal to get the same performance.

[leander311]

Yes, larger flex duct can have the same friction losses as smaller metal duct. But then you have lower velocities and greater surface area per length, which means more conductive losses through duct walls, reducing effective efficiency.

[smadave]

I agree with dash. If you know how to use a ductulator properly you can move mountains. All metal duct systems IN GENERAL tend to resonate making more noise. You can make metal system airtight by simply using mastic on all the joints. I'm assuming we are talking about a basement..flex in a basement looks like $hit, but what are you gonna do

Dave in NJ