I'll focus on the HVAC side since I don't know much about direct vent hot water tanks. The quote provides enough information about what they plan to do which gives me a good feeling about this installer. However since you are providing the equipment, the quote is high in my opinion. Sounds like they are still quoting the job as if they provided it and marked it up. I think it can come down at least $5k. Who is providing high voltage power to these units, or is this an additional cost paid to another contractor? Also to clarify, will there be multiple returns on the first floor as well or one central return in the living room? I would clarify with the dealer about the ductwork system. By the quote it sounds like it is all hard metal, with no flex duct even in the attic where it is common. If this is the case, great. This could account for why the quote is on the higher end. I would strongly consider upgrading to the 15 SEER condensers if the unit price increase is not more than a couple hundred per unit. They should be quieter and are overall nicer units in my opinion even if they have the same cabinet. Another upgrade to look into is a high efficiency media filter for each unit. They typically get replaced every 6 months or in some cases up to a year, and they provide better filtration of the air and hence protection of the equipment. These may add a couple hundred per unit installation.

moonsoon first and foremost, as said in my previous post, you need a load calculation in writing broken out by each zone. I believe 10.5 tons is grossly oversized. EACs refer to electronic air cleaners which I believe the GAPA is Carrier's model. You need some type of air cleaner for both systems. EACs are not a cure for asthmatics but may help. Don't know about the GAPA model but most require regular cleaning/maintenance and do produce a small amount of ozone. I would not have one personally. I have a 5" pleated media filter that I change once a year. I lean toward the KISS system(keep it simple stupid!). No offense intended. The "return" air recirculates your inside air. It has to be sized to be in balance with your "supply" air. For example, if you have a 4 ton blower, your ductwork system should be sized accordingly-1600 CFMs both supply air and return air. One large return such as listed in your original post with such a large space will give poor airflow/exchange and most likely will be noisy. That was the reason for my suggestion for another return. And definitely don't place it in a living area-they should be centrally located in your home normally in an inside hallway. again I know that electric rate is not correct but I will not beat a dead horse. I do think a homeowner should have an apprx idea of their utility rates. what are the tier electric rates? I don't have a strong opinion on UV lights. Most homes don't have them and I would think they would be better indicated for areas with high relative humidity or to focus on specific problems with your evap coil. You do want Carrier's tin plated coil not the copper models. as far as ductwork, metal main trunk lines that are insulated with flex for supply and returns would be my choice. check with county building office and see what code is for new construction. IMO

The biggest problem with HVAC zone systems is knowing when to choose it as a solution and when not to. Some HVAC companies it's about "sell, sell, sell" whether or not it works... there's more money in "sell, sell, sell" --- when it's only about money? So does the comment above mean I do it for free? No. If you think that you are reading things that aren't there. New construction? best to choose separate systems 9 times out of 10. In order for a zone system to work, you have to know what you are doing. Most HVAC companies staff (the techs they send you) are 20-30 year olds. How much practical experience could they possible have? It's best for HVAC zone systems to be an elegant solution. A HVAC zone system is a tool in the tool bag. Not all homes are suitable for zone systems. Some homes there is no other way, and in some cases complications to those problems will make an HVAC zone system design possibly more prone to problems. You have a problem now, do you want more problems. These decisions among others are decided "in person" --- so considering that becareful what information you decide upon from the internet. Just because it's here doesn't necessarily mean it's true. That said: Depending on equipment level chosen, how many different floors you have in your structure, how much room you have available... will all be factors that make you decide one way or another. From there it's in your best interest to pick a contractor that is skilled: especially when it comes to HVAC zone systems. (there's a lot of garbage out there.) (click to enlarge if necessary) I service the Katy, Texas area.

Wayne, The Goodman furnace model you posted is a top of the line Modulating gas furnace also according to what you posted it is replacing a 100K 93% gas furnace that is 20 years old. Modulating means this top of the line gas furnace will modulate based on the heat load needed to heat the home. The homeowners that are suggesting you to reduce the size of this furnace are doing so without running a heat load calculation. (They often tell you to do this --- but they never practice what they preach.) Nor are they taking into consideration that your current duct system is probably sized for a 100K BTU furnace. So you put in the 80K BTU furnace without addressing duct work etc... nothing but trouble. (20 years is a long time to run a *supposed* over sized furnace----- if it doesn't make sense? You're in the fiction section of the internet.) If this were a new home build in 2020, yeah an 80K BTU furnace *MIGHT BE* the better choice. Amana top of the line model is: AMVM97 Thermostat: I would stay away from the Nest. Other than that either the Amana or the Goodman can be controlled with any off the shelf thermostat. If you want to control it from your phone I would suggest pairing it with Honeywell stat that works with Honeywell Redlink. Your HVAC company should be able to set this up for you. Either the Amana or the Goodman (top of the line) furnaces are good choices for your climate. Modulation of these start in the 60,000 BTU range and gradually heat up as the load dictates. As cold as your climate gets I would go with the 100K BTU model ------- you've got 20 years under your belt with the old one. How much more proof would you need on sizing? If it's on the internet it must be true? yeah we know how that turns out......