HERS Rating

Brian_24

The return air duct will have to be tested as well. You can use flex duct just be sure to seal everything with plenty of mastic. Also be sure to seal your duct penetrations at the ceiling or floors where your registers will go. Good luck,
Brian

Unknown

HERS Rating

To comply with state energy requirements, the building I am working on must have the ducts tested by a HERS rater to ensure that the ducts do not leak more than 6%. Do return ducts typically apply to the rating requirements (this project is in California)? If so, would that rule out the use of flexible return air ductwork, or could it be tested at a positive pressure rather than negative.

Any assistance would be appreciated.

Unknown

hers rating

Can flex duct handle the negative static pressure? What negative is the ductwork normally tested at?

Brian_24

duct testing

It depends on the leakage test method your rater uses. Some use a duct blaster or there is a modified duct leakage test using the blower door. Neither test uses an extremme amount of pressure. The flex duct should handle it with no trouble.
Brian

Unknown

HERS Rating

Thanks for the feedback Airhead. Are you saying that return air ductwork could be tested at a positive pressure? If it is tested at a negative pressure it would pull in the duct walls wouldn't it?

Dave

Brian_24

If a duct blaster is used the duct will be under positive pressure. If the modified blower test is done it will be negative. Neither test is done with enough pressure to colapse flex duct, Hope this helps,
Brian

Nick Wilder_2

Duct Blaster testing is usually done at 25 Pascals (0.1" wc). Blower door testing is usually done at 50 Pascals.