had to google ptcs Performance Tested Comfort Systems PTCS Certification is an important qualification for contractors working on HVAC systems such as furnaces, air conditioners, heat pumps, and ventilation ducts. PTCS certified contractors are trained � and held accountable through third-party inspections � to evaluate your entire house as a system when installing a new HVAC system. In many cases, you may be able to replace your existing furnace, air conditioner or heat pump with a smaller (and cheaper) unit if the installation is accompanied by air sealing, insulation, duct sealing and other efficiency measures. The program is limited to the Pacific Northwest, including Washington, Oregon, Montana and Idaho. If you live in one of those four states, you should look for the PTCS Certification when evaluating a contractor to do any HVAC work for your house. ___________________________________________________________ ok enough of that pic by pic comments: Pic 1 hard pipe supply plenum (silver) with black flex suppy duct see the failure of the duct tape? the duct tape should be removed. black jacket and insulation folded back and take off mastic sealed to hard pipe plenum. not only the take off but also the inner liner of duct to take off. let dry. insulation and jacket pulled to plenum in full contact and mastic sealed. I would use paint on mastic for the seal to the plenum and mastic tape to secure jacket to ductwrap of plenum. pic 2 & 3 see above pic 4 your vapor barrier should extend up on the walls of the crawlspace and be sealed to walls pic 4 this is where the hard duct plenum reduces to smaller size..the joints here leak also. but opening the duct wrap and mastic sealing these areas would be a LOT of work. you may want to seal major leaks first and see if performance improves before tackling the sealing of hard pipe. It is curious that the pipes seem to be insulated with batt insulation rather than pipe insulation see pink insulation wrap on pipe going thru block wall. this may be to condensing unit? so do you think you may take this job on or sub it out? if you sub it out make sure that you have duct leakage numbers before and test to get reduction numbers afte sealing. also take a look at the job in progress to make sure that mastic or mastic tapes are used. best of luck.

If your talking about cutting into that 6x6 on the picture, dont do it. That's a pretty beefy piece of structure probably holding a fair amount of load. Hard to tell orientation and what it supports from the picture though. I couldnt see anyone putting that large beam there just for the heck of it.

It is frustrating to me that the original builder chose to install the HVAC system in attic in a house as big and expensive as the one you have described. Unfortunately that is the way it is in many parts of the country. I am not going to attempt to comment on "Y" connections versus remote distribution boxes. I am not a duct expert and it is difficult to follow this without a detailed diagram. So I will give you me general thoughts. I think the main distribution trunk should be a metal duct and well sealed and insulated. The size needs to be equivalent to 18 inch diameter. The flexible duct branches should be R6 or R8 rated. It should be as straight as possible and not looked like a mess. The static pressure at the air handler or furnace ideally be 0.5, anything above 1.0 is not acceptable. Adding more returns is a good thing in that you can never have too much return air. The bedroom probably needs more than two supplies. I hope you have ceiling fans to mix all the stagnant air up at the ceilings. If not consider installing them.

Is the duct work in good shape? Does it need replacement if it didn't have the nicotine issue? The $6K quote seems high. Did the contractor say how many days it would take to replace everything? You can get more quotes to see if you can get a better price, or validate the quote you have is the reasonable. You could take a chance and install the new furnace, run it and see if you smell any nicotine. It may turn out the amount of nicotine in the duct work is small and not noticeable and you don't have to spend the $6K.