Poorly balanced HVAC--critique my plan

[Genny Li]

The HVAC duct system on my condo was designed horribly.  Here is my plan to address issues.  Please tell me what you would do in my place instead.

LAYOUT:

There is a separate HVAC system for each condo, with the compressor outdoors and the air handler with the only return grille in the great room.

The great room is long and skinny with 2 suites on each side, for 4 suites in all.  There are 2 long trunk ducts that serve the whole condo.  On one side of the great room, you have a single trunk line duct serving Bedroom 1 & Bath 1 from a soffited/bulkheaded duct in the laundry closet off the great room, then the main great room duct next to the return/air hander (also in the laundry closet), and then Bedroom 2 & Bath 2 from the soffitted/bulkheaded duct going through the WIC for suite 2.

There is also a duct that crosses the great room (between the floor joists of the next floor, of course) to supply trunk line 2.  I believe that it may go straight from air handler across in the middle of the great room (because anything else would be stupid), but I haven't checked.  Trunk line 2 goes through soffits/bulkheads in the closets to provide AC to Bedroom 3 and Bathroom 3 and Bedroom 4 and Bathroom 4.  Once again, because these people are geniuses, BOTH the bedrooms have supplies on the ends of the trunk line.  Another soffit/bulkhead goes through off the truck line in bedroom 4 to the kitchen in the great room, but I don't really care about that.

All bedroom vents are 6x10".  I think the bathroom are 6x8"

The ducts are all built out of rigid insulation coated with duct material. This is/was pretty common in applications where you want to minimize sound transfer (like a condo).  But then it gets weird.  All but two of the bedrooms have more of the insulated duct material blocking the entire vent a short distance before the air supply vents, with only a small hole cut out of them--probably 3" by 6" in the bedrooms, and down to about 2x5" in the bathrooms.  This appears to have been done when the ducts were fabricated!  They're basically jerry rigged dampers.

Bedroom 1, which is one of the two closer bedrooms and the one that doesn't have these special permanent "dampers," is super cold most of the time.  It's on the cold side during AC season even with the vent closed.  (This is an AC-dominated climate.)  The bedroom is also the most interior of the bedrooms in the building, being entirely shaded.

Bedroom 4, which is one of the farther bedrooms and the one that doesn't have one of these special "dampers", get particularly hot.  Bedroom 3 is a little hot, while Bedroom 2 is fine.

PLAN:

The most obvious thing to do with any system with no dedicated air returns is to just add them, which is pretty trivial with the way the condo is laid out. No jump vents will be needed.  I will just use the stud bays in 3 of the rooms. Because this is an AC climate, I'll put the return grille high in the bedrooms and low in the main room.  One of the rooms will need an over-the-door through grille, and the Tamarack ones with the cardboard baffles actually work remarkably well.  That's $48 for the grilles for 3 rooms and $70 for the one Tamarak one (oooof), but still not bad.

This alone should drastically help the HVAC distribution, especially if the fan is kept on, and the fan isn't very expensive to run.  However, there is no way that the air handler is happy with the current extremely restricted air flow--while at the same time, the air flow to Bedroom 1 is way too high.  So I currently plan on doing my own redneck baffle for Bedroom 1, reducing the air down to no more than half of what it is now, while also cutting the holes larger in Bedroom 2 (which actually isn't either hot or cold right now) and Bedroom 3 (which is running hot, being on the southwest corner).  If Bedroom 4 doesn't get more air after this, then I can go back to tweaking register settings.  I think I may need to increase the air to through the main great room register and restrict the one in the kitchen to help Bedroom 4, too.

I plan to leave the bathrooms alone for now.  They aren't uncomfortably hot.  But I am planning on linking the fans to a moisture sensor instead of the light in the future, because one of the mirrors has moisture damage since the fan goes out the moment the light does (and so to many other mirrors in the complex), and the fan is also continuously running at other times when it doesn't need to be.  I figure that this may lower overall HVAC usage, but if it doesn't, then it will at least help in removing all excess moisture after a shower!

QUESTION:

Would you do something different in my situation?  What would you do? :D