Insulated flexible duct r6 silver jacket is used in standard heating and air conditioning hvac systems and some venting applications.
Flex duct in attic.
When these ducts are exposed to exterior air the plastic jacket never gets cold enough to permit condensation because the hot attic air keeps the plastic jacket warm.
How to hang flex duct in an attic 1.
The higher in the attic the hotter it is.
The attic is a hot dirty nasty place.
The lower the cooler it is.
People can not carry ladders up into a attic and them place them onto 1 1 2 wide boards so they can climb over ducts.
A layer of insulation covers this thin layer of plastic and blocks the heat from getting in or out of the duct.
It s done this way because it s easier and cheaper to run a flex duct through a wide open space than to fit it through and around floor and wall framing.
Flex ducts consist of a spring that is wrapped with a very fragile layer of plastic.
Not part of what is in the attic.
They just tear through them smash them climb on.
Just blow the attic to r 38 and over the top of ducts if needed.
The attic ductwork is flex duct work.
Ductwork running along an open ceiling in the basement of a one story home is also more affordable to replace.
Recently i had another hvac company come out and put in a new bathroom vent and they told me they believed the duct work was full of water.
The supports need to be at the manufacturer s recommended spacing but no longer than 4 maximum.
Ducts up high get tore up.
Ducts are to be part of what is inside the house not part of.
The duct has r6 insulation which contains 33 more insulation than the standard r4 2 product.
The straps that hold up the flex duct need to be no less than 1 5 wide.
Around that is the outside cover of the duct itself.
Hold the loose end of a roll of duct support webbing against the side of a roof joist sitting directly above the flex.
Secure the webbing to the joist by hammering a 2 inch roofing nail through the webbing and into the side of the joist.
The master flow 4 in.
It also makes maintenance and or modification easier.
If ducts are to be installed in a vented uninsulated attic or crawl space hang the ducts with supporting straps or saddles of sufficient width and frequency to adequately support the ducts so that the ducts do not sag and are not pinched or compressed in a manner that would cause damage to the ducts the duct insulation or the duct air barrier covering.
The official recommendation from the adc is that flex ducts should sag no more than 1 2 per foot of length between supports.
Type of ductwork system the least expensive duct system is a radial system of flexible ducts in an attic running to ceiling grates.
Those are valid reasons to do it so the real answer is to make the attic at least semi conditioned space.
Blown in insulation is cheap.
The costliest are sheet metal ducts running in enclosed walls and ceilings.