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.
Using flexible duct for heating.
Insulated flexible duct r8 silver jacket is used in standard heating and air conditioning hvac systems and some venting applications.
Manufacturers then cover the tube in fiberglass insulation.
This additional insulation provides greater thermal efficiency to save energy.
When you want to heat and cool the house efficiently you need to allow as much airflow as possible through the ducts.
Ideally ducts shouldn t sag more than inch per foot between supports and maximum sag should not exceed 2 inches 4e.
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Using this kind of ducting is best in tricky spaces where rigid ducts are not just possible to install.
The duct has r8 insulation which contains 50 more insulation than the standard r4 2 product.
While those that sell flexible ductwork may have you believe otherwise it does not allow as much airflow as a similar sized metal duct.