I had Strand Brothers come by. They were excellent to deal with. Their sticker is on the unit, so I called. The guy came by and confirmed what y'all posted above about having 2 6in duct tubes, one high, one low. One is in place, the other I may have put in, so I can close in the ceiling so no more insulation falls in. He said that since the door has a good gasket seal and since the small closet is insulated, I won't notice any difference in the a/c bill if I close in the ceiling. I may do it anyways, just for aesthetics. Thanks for your help here. Mason

Are all of us on the same page? As I understand it the OP is talking about constructing an air tight and insulated mechanical room around 1 heat pump and 1 gas furnace 5 ton cooling coil combo. Said room is to be heated and cooled by one or both units. The goal is to gain energy effeciency, reduce rust on the 5 ton unit and prolong it's life. I believe it's a novel approach with several oppertunities in making wrong turns. When I mentioned seeking the services of a ventilation engineer it was in lieu of taking a harder stance and reccomending Op forget the whole idea. I can't give a link that addresses this situation but my collective knowledge of hvac lead's me to believe it will not give desired results. Finding myself alone in this opinion deserves rethinking if there are rebates to be had. If this qulify's for rebate,point me to it so I might join the informed and lay aside my old school reasoning. A strong case could also be made here if reccomendations for keeping equipment in conditioned space during new construction could be sited. Evidence of gas heat being common pratice for close quarters like computor rooms would cause me to rethink. What concurn's me is the sheer size of a 5 ton blower in such small space with supply and return air shared with living space. I can see where induced combustion helps but it is still akin to balancing a nail on it's piont. I share the opinion that keeping ducts within conditioned space is a good idea. What I can't see is construction in the attic for the purpose of bringing ducts into conditioned space. Inclosing equipment in an existing attic then conditioning the space sounds unpresidented.

How tall is this attic space? How large are the joists in the "floor" area and what spacing do they have? How deep are the roof rafters and what are their spacing? What is the current attic ventilation? How would you plan to access the space with a stairway? There are certain minimum height requirements for living space, and the requirements for supporting live loads differ from those of just storage. Stairways have to have a certain rise and length for the height involved and eat up a lot of space. Where do you envision that space to come from on the second floor? Your project may be more involved than you think, or completely undoable depending on those factors. You need a site visit from a structural engineer, architect, and contractor to determine if what you want will even be doable. In the meantime, plain (not architectural) asphalt shingles are a fairly cheap item and well within most DIYers ability to install. Which means that they can be considered sacrifice at a later date if your other plans come to fruition. But, you need to take steps to protect your home from leaks, so needing a roof trumps all of the other "what ifs". As far as the ductwork goes, rigid ducting is far superior to flex duct. There is no need to replace it at all. Just make sure that the transitions are properly sealed and add additional insulation if you desire.

I think that the condensation is more from leaky duct takeoffs & plenum to equipment connections that are poorly sealed rather than a gash in ductwrap. although you don't say how large or where the gash is located on the supply plenum ductwrap. and...no it isn't as easy as it looks...if you do it properly. first remove all duct insulation. seal each duct take off with mastic or Hardcast brand mastic #1402 tape. (surfaces must be clean & dry) paint on mastic will take time to dry, mastic tape must be firmly pressed in place to make seal. paint on mastic should be thickly applied.. like thick as a nickel. you'll have to cut the ductwrap to fit around the duct takeoffs. I usually take ducts off, so that I can put the ductwrap with precut holes for takeoffs. take time to seal plenum to equipment. I find that the mastic tape works best for this. you don't say if plenum is upright or trunk line...so most common would be upright. wrap the ductwrap around the plenum, leaving top for seperate piece. tape covers duct staples. so you'll need a duct stapler, duct staples & fsk tape (foil scrim kraft tape...looks like ductwrap without the insulation) double row of staples, fsk covering staples..and I then staple down fsk. ductwrap is sold in 4' wide rolls. buy R-8 only. one side of the ductwrap is blunt cut...meaning ductwrap and insulation are same...the other side the insulation is cut back less than the insulation...this is the side that is stapled to the ductwrap. staples can't penetrate ductwrap & insulation to attach to the ductwrap under the lap..so any areas to be stapled need to be cut back in the same manner. once you get ductwrap on sides of plenum installed, then cut piece for top cap of plenum. make sure insulation is in full contact with the top cap & make the lips (ductwrap without insulation) about 3" wide. use these lips to staple to wrap on sides of plenum. fsk tape, staple. then re-attach the ducts. insulation of ductwrap has to be in full contact with metal of plenum...or it will continue to condensate. make sure you pull it tight enough to be in full contact but don't compress the insulation. duct & plenum to equipment connections has to be completely sealed or it will continue to condensate. ducts attached to takeoffs on plenum...insulation in full contact with both start collar of takeoff & plenum. inner liner (flex) mastic taped to start collar. outer liner of flex covering insulation at plenum & mastic sealed to plenum. some people use lock ties (pundit straps) be aware that compressing insulation with lock ties will cause condensation, and that lock ties alone on start collars will work loose...even with racheting tool...over time.. I like to mastic seal the outer liner (the vapor barrier of the flex) to the vapor barrier of the ductwrap. for ease of install & to save time...mastic tape. it is a hot, uncomfortable job that requires patience & much attention to detail...or it will condensate. look to spend $100+ for ductwrap $50 for duct stapler plus staple costs $30 for hardcast mastic 1402 tape $20 for a bucket of cci 181 mastic & brushes can't remember price of lockties or tool to tighten as I hardly ever buy lockties or use the tool I've had for years. buy two rolls of Hardcast 1402. this tape seals to many materials as long as they are clean & dry... use the other rolls to seal supply boxes, if you take off a supply grill inside the house, you'll see the oversized cut where the supply box penetrates. keep tape within area covered by supply grill. also take down bath fan covers & use mastic tape to seal those oversized cuts. other tapes don't seal like this particular brand of tape, over the years I've tried them all. hardcast 1042 is what works & lasts. if you hire this out...make sure that the work is done as described above..if you diy & have questions.. post or email me. and if existing ductwrap is cold on the bottom..it is probably wet inside. best of luck.