Sorry for resurrecting an older post, but the WAF is increasing as I delay in our build and try to gather as much info as possible about HVAC and figured it better to resurrect than start new. My HT has the main trunk running 1/2 way into the room, then with 4 supply branches (5" round, metal) coming off the end (3 to feed other rooms and one for the HT. There is a RA in the back of the HT room as well. Here are my questions:
1. If the entire system (trunk and branches) is encased in a soffit with insulation, then RSIC/DD/GG, is that enough to dampen the outside, or should MLV or equivalent be wrapped around the outside of the duct work before insulating?
2. Without replacing the current duct work with acoustic insulated flex, is the only way to deaden the sound entering into the HT supply run to take apart the current metal, wrap the inside with duct liner (as Ted mentioned) and put back together? Would an HVAC guy be able to do this better (ie quicker and easier) than me (with no experience)? Would cutting apart and using a duct muffler be easier?
3. If I were to use flex duct, would all of the branches coming off the main trunk need to be replaced, or just the supply in the HT?
4. If the RA is nothing but a hole at the bottom of the wall, running up between two studs (with drywall on each side of course) and entering the main trunk, does the inside of the drywall need to be lined with MLV or equivalent to deaden the sound going back into the main line?
5. The main trunk actually has an additional supply cut right into it for the HT. I know this is a BIG no-no for sound reduction from what I've read, but my HVAC guy thinks I should keep it just in case, and fill it with styrofoam or something if/when it's not needed. Does this make sense, or should I just have him seal it off now, even though he doesn't think one supply will adequately heat the room (11x17)?
6. Please tell me this is all worth it.