I've been doing some reading, lots of reading, LOL, and came across an article saying that home designs like ours, two stories with a vaulted entryway and staircase are a nightmare for HVAC. It recommended two systems: one up, one down for real comfort and said it was really more economical than a two-zone single system. We've thought about putting a second unit in the attic, but it's something that probably has to wait until the house is paid off. In the meantime, I've been thinking and finally realized that there is a place we could put another supply duct. It would be on the far side of the door into the garage. The current duct trunk is on the other side of that door. It's right above the closet in the guest room, so we should be able to go through there and straight up to the attic--hope the attic joists aren't in the way. The run would be about 10"-11" x 24" in size and approx 58' long with 2 right angle turns. We're thinking it could handle about 900 CFM and hoping we could take our master bedroom and vaulted ceiling bath off the current duct and supply them with that. Our bedroom gets a little, but our bath is at the end of the current run and gets basically no air. With our master suite off the main trunk, I'm pretty sure the other upstairs rooms would have plenty. Does that sound like a duct that would work? Hubby is also thinking that if we did it with ductboard, he'd be able to do most of it himself, except for the connection to the plenum. He's pretty good with carpentry, plumbing and electrical, but has only worked on a/c in cars. And if I hadn't mentioned it, after measuring our house, we're really around 2,600 sq ft, not the 2,400 sq ft we had thought we had. Sorry, one more thing, if we have 1410 CFM now and add 900 CFM with another duct, going to about 2500 CFM, does that mean we'd need any certain blower size? Or do we just go with what the manual J says, assuming I can find the manual or a tech to do the calcs for us?

@tigerdunes & mike_home: Contractor 3 & 4 I have felt good about. Contractor 3 initially added small amount of R22 free initially. He must have gotten very busy/ or tired of my questions as his responses have slowed down to grind. Finally heard back form Contractor 3. He stated "supply plenum is large enough, they can re-build return plenum for $225. He is using a slab coil because airflow would be better, Supply plenum for A-COIL would be smaller" He said supply plenum is big enough w/o rebuilding. I requested he price out Option 1 with Carrier Infiniti with the 58CV(A,X)090-16 furnace instead. He stated "Again furnace was chosen for airflow. 58CV(A,X)090-16 IS ONLY 17” WIDE instead of 21”, Smaller plenum". Did not re-price. Contractor 3 said keep in mind Perfect Fit filters cost 3X of Aprilaire. Final Prices incl similar duct work repairs w/ utility rebate, instant Trane rebate for T-stat. Contractor 3: $11,267 total. Can't fit me in on schedule til 1st week of May. 3-4: Trane XR17 (16.0/13.0): 4TTR7048A1, UD2C080G9V4, 4TXFH054CC3, XL824 Scope: Rebuild return plenum and keep supply plenums (slab coil), R-8, 2” of insulation, auxiliary drain pan, condenser pad, float switches, programmable thermostat, adapt to copper lines, gas connections, seal duct where needed, adapt to vent pipe, electrical, correct size circuit breaker, mechanical permit and inspection, labor, supplies. - Install Perfect Fit media filter. - Replace damaged ducts above second floor (5) & utility (1) and seal flex duct connections - Add supply grille in upstairs office or hall where possible. - Add return grille (12 X 12) in hall ceiling. - Increase duct size feeding kitchen/nook area and 4ft duct board trunk line for better airflow - Replace supply register (15) with wide vane grilles, weather-strip and seal register boots from inside. Contractor 4: $11,463 total. 4-2 XR17 (17.0, 13.5): 4TTR7048A1, UD2C080G9V4 4PXCCU60AC3HAA, XL 824 Scope: Build new supply and return plenums w/ 1 1/2" Owens corning fiberglass duct board (A coil). Add new drain pan, electrical disconnect @ outdoor unit, electrical whip, copper fittings, PVC drain line fittings, gas flex/ gas fittings, exhaust vent, slab as needed per unit specs and city code requirements. - Install Perfect Fit media filter - Transition trunk/branch lines feeding master bed room side and upstairs to new plenum, remove any hard 90 degree turns to provide better air flow to upstairs areas. - Install damper collars on all three flex lines @ front of plenum to provide a means to adjust air flow - Increase sizing of flex (8" to 10") to supply kitchen and nook, remove the distribution box and "Y" off 7" to nook and 8" to kitchen register to provide better air flow to these areas. - Replace all owl flex that is broken open @ upstairs attic (5 drops) & utility (1 drop) with R-6 metallic coated flex ducting. - Cut in new 12"x12" return filter holder grill at upstairs hallway w/ 10" flex to return box @ unit. - Seal all duct work with UL listed metallic tape and mastic to prevent air leakage. - Replace supply register (15) with wide vane grilles, weather-strip and seal register boots from inside.

Violate MFG Warranty: only if it was the wrong kind or installed improperly causing damage to the compressor. With that said, most modern HVAC compressors do not need hard starts these days. Usually, if one is required to start a compressor it typically indicates failure of the compressor. While you can 'sometimes' install a hard start kit to save a compressor sometimes this only lasts a short while. Typically what this means is that the bearings with in the compressor are failing. (seizing up) and so the compressor doesn't have enough power to start on it's own. By adding a 'proper' hard start kit (there are many configurations, because there are different types of compressors / different sizes in tonnage --if you use the wrong kind for the wrong compressor it can damage the compressor in addition to the damage that required you to install the hard start to begin with.) The best is a 3 wire hard start kit in which your HVAC contractor chooses the proper start capacitor as well as the starting relay. As mentioned earlier there is a bunch of different kinds. A knowledgeable HVAC contractor will know which kind you need. Others will just put in a packaged 'kit' that probably won't work for very long in some cases.

I should preface my comments by saying that while I consider myself to be practical, I'm not an engineer or a person who is militant or uber-motivated about building science. I like to do what is practical without going to the n-th degree with what may be possible (and ecologically sound) but not economical. We've beefed up our attic to a bit more than R-30 but took the advice of the insulation contractor who said insulating the floor was probably not worth doing. We have put in double windows throughout. I have a house about the same size as yours. My enlightened HVAC contractor had originally proposed 6 tons of cooling but agreed that 5 tons would probably do fine. It has been fine, long runs and very comfortable on the hottest days. With that in mind, I'd be concerned that 3.5 tons may be a shade small. 3.5 tons is 42000 btuh and since your load calc is at 44K, I might round up the small amount to 4 tons (48K) rather than down. It's a small difference but I'd rather be off slightly (and only slightly) on the high side than on the low side. You've cited a modulating furnace and that should provide good comfort. One concern, and a reason why I avoided a variable speed unit, was the thought that the fan operating at a low speed might not push much air to the far end of the ducts. My contractor agreed with that as a concern and so we didn't go that route. My house is > 100 feet long. If your HVAC contractor says that the max performance would come from a thermostat of the same brand (ie, Bryant), I would go with that. All up-market units have internet accessibility, you should be most concerned with its function. HRVs? I think these aren't common in our area except for the newest and tightest houses. Mine's about 50 years old and I like a small crack in a few windows, and sometimes with a bathroom exhaust fan running, to bring in fresh air. Good luck, take my comments as just one guy's personal opinions. PS - I too have Bryant equipment and am about to buy more for a second house. I'm very happy with it. But more important is having a great contractor. Good equipment doesn't make up for a crappy contractor.