We're looking at a couple of solutions;

1) A secondary floor (2x4 frame + sheathing + pan) built on isolators sitting on attic/loft floor.

2) A secondary floor (pan) suspended from the roof trusses with isolation hangers & threaded rod.

In a couple of runs to bedrooms we're putting in a couple of overside wide sweeping bends in the ducts to help isolate fan noise without increasing static pressure too much.

Recommendations on this still very welcomed. We're quite nervous about the placement of this system.

Thanks,

Aren't you in Minnesota? I can't imagine having HVAC equipment in an attic is a good choice. Very cold in the winter and hot in the summer. You're building a house, why not provide a more useful location with less temperature extremes?

Otherwise, don't you have the option of locating it other than above the bedroom?

Yes. It's a fully conditioned attic. More like a loft than attic. In the last photo here (http://bamasotan.us/2018/08/drying-in-windows/) looking through the loft you can see the open stairwell down to the 2nd level hall. The HVAC room will be just the other side (south) of that stairwell and then my office just beyond that on the southernmost end.

I'd like to have put the HVAC on the north end but they cannot get the ducts from there to where they need to go down which is the same as where they now plan to put the equipment.

Noisy ductwork/equipment = bad duct design,fan speed not set properly, high static pressure on the fan unit. undersized ducts.

I would do a static pressure test to determine the next step.

No HVAC duct or equipment has been installed yet (likely begin next week) so this is looking purely at what needs to be done to insure as quiet and vibration free a system as possible.