Manufacturers then cover the tube in fiberglass insulation.
Using flexible duct for heating.
Flexible hvac ductwork this type of ductwork is usually tube shaped and is made from a wire coil covered in a bendablebut durable plastic.
Ideally ducts shouldn t sag more than inch per foot between supports and maximum sag should not exceed 2 inches 4e.
A good rule of thumb is to provide a duct support no less than every 4 feet and more frequently when using large diameter flexible duct 4c even when ducts are partially supported by framing members 4d.
This additional insulation provides greater thermal efficiency to save energy.
While those that sell flexible ductwork may have you believe otherwise it does not allow as much airflow as a similar sized metal duct.
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Since it is so flexible it is also easy to obstruct the airflow even more.
The master flow 6 in.
Insulated flexible duct r8 silver jacket is used in standard heating and air conditioning hvac systems and some venting applications.