Central Air-Conditioner Installation Duct Questions

Hello,
I'm a newbie at home improvement, so please forgive my initial ignorance when it comes to the technical terms.
I recently contracted with a nation wide vendor to install a central air-conditioning unit in my ranch style home. This nation-wide vendor sub-contacted with a local installer who performed the actual work during May of 2004.
The blower was placed in the attic, with flexible duct work running to the ceiling in various rooms. A large cold-air return was placed in the central hallway ceiling.
During the first year I had several problems with the installation. (These included the blower drain that didn't function properly (causing ceiling damage) and the cooling ducts separating from the vents in the ceiling. These were repaired quickly and without question.
Fast-forward to today. I switch the unit on and realized that the unit wasn't cooling properly. I contacted the nation-wide vendor who dispatched a heating and air specialist to my home. The specialist arrived and proceeded to tell me that the duct work that was attached to the blower unit had "collapsed in-on-itself;" specifically where the flexible duct work met the intake end of the blower unit.
Apparently the original sub-contractor installer used semi-flexible foil faced insulating sheeting to construct a connection from the flexible duct work to the intake end of the blower. This same sub-contractor also created a large box (for lack of a better term) of this same semi-flexible foil faced insulating sheeting and attached it to the ducts with foil tape.
So, my question(s) is this:
Is it typical to connect flexible 6" or 8" ductwork to a blower type unit with 1/2"foil-faced insulation sheeting? In other words, isn't there some type of reducer or pre-fabricated part that performs this function?
Since I have one large central cold-air return, is there any pre-constructed unit that should/could be installed in place of this taped amalgamation? My current setup is a 3' by 3' box that is surface mounted to my ceiling with a 12" flex duct tube going from it to the cold-air intake of the blower.
Is there some type of building code that dictates what or how these type of constructions should be constructed as? Obviously, each town/area has its own regulations, but what should I look for when researching?
Thanks,
Shawn
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I have seen boxes (Return plenum) made of that foil faced insulation board. I never thought much of them, but the ones that I saw were functional. The best way that I know of is to have a sheet metal fabricator make a box to the specifications that you need. You should make a drawing with multiple view points and all of the dimensions. Include any openings for duct connections. You can also have a filter compartment built into it. Take it to a sheet metal fabricator and they can give you an estimate as to the cost to make it. You can buy duct wrap and insulate it yourself.
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It sounds like a terrible install, but pictures would be helpful.
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The material which you are talking about is known as "ductboard". The other poster is correct in that insulated sheet metal is the best way to go. Around here (San Antonio) sheet metal hasn't been used in residential for over 30 years. It went from systems entirely of ductboard starting in the late 60s, to ductboard boxes on the supply and return hooked up with flex duct in the early 80s. Ductboard can be ok IF done correctly, which yours must not have been. The company I work does only replacement of equipment (no installations in houses that did not already have central) We use ductboard to transition to the existing ducwork as needed, and usually systems like yours if we replace existing ductwork. I always use mastic sealer designed for the purpose, and seal the iniside and outside of all the ductboard joints I do. Once it dries and hardens, you couldn't get it apart if you wanted to. Bottom line: try to get yours replaced with sheet metal, but if they will not do so, insist that ductboard be done properly. If the "national company" you are talking about is Sears, you have my sympathy. Stories like yours are commonplace with them around here.
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