"Can I talk to the HVAC person about the best way to heat and cool my house?"

Passive House - Fresh Air System Install & Costs (Zehnder) - YouTube

The Problem with Heat Pumps and Cold Weather - YouTube

You'll want a blower door test.

I suggest you meet in person with the HVAC contractor at the house. This will give you an opportunity to ask questions and express what is important to you. Did the builder already budget an amount for HVAC, or it this something to be discussed?

The best way to get even temperatures on a two story house is to have an HVAC system for each floor. I have this arrange in my house for a similar sized house. Both furnaces are in the basement. Installing the furnace and the duct work for the second floor in the attic is not ideal and should be avoided if possible. A 2-stage furnace operating in the low stage will be quieter than a single stage furnace. The other source of noise is undersized duct work. The ducts sizes need to be able to handle the air flow. A well designed HVAC system can be quiet.

For a major renovation you want the the HVAC contractor to do a heating and cooling load calculation. This involves entering all the data about the house (size, insulation, orientation, etc) in a software program. The program calculates how many BTUs of heating and cooling are required. Many HVAC contractors want to use rules of thumb based on the square footage of the house. This lead to the equipment being the wrong size. If the HVAC contractor is unwilling to do a proper load calculation, you should think about finding another HVAC contractor. You should also investigate the HVAC contractor's reputation. Incorrectly installed equipment will always have problems which are difficult to correct.

I looked and Zendher a few years ago for our design. They were pretty expensive and the ROI couldn't be justified unless I lived to be about 238 years old

You may well find, as we did, that with serious insulation upgrades and rigorous air sealing the draftiness and unevenness may well pretty much disappear, no matter what you install for HVAC equipment. In terms of noise, we have a lot less just because the furnace runs a whole lot less; not at all at night when we set the temperature back, for a while in the morning to bring the house up to daytime temperature, then not much during the day. There is slight continuous background hum from the ERV system, way less noise than the furnace makes.

One of the real benefits of insulation and air sealing is that it is pretty reasonable to expect it to continue to pay back for 100 years, if not 238. It also allows one to install much smaller and less complex HVAC equipment.

I would want to make sure the contractor will perform a Manual J load calculation to properly size the units.

We built in 2021 and used a VRF System ... Variant Refrigerant Flow.

https://www.csemag.com/articles/back-to-basics-vrf-systems/

My DH has always been unhappy with standard hvac systems and this was our opportunity to get a custom system. The problem is that any system is only as good as the person who designed it and the hvac engineer got plenty of things wrong. After living with the system for a year, we now have another company in to reconfigure the system and it is going to cost $48K. Crazy, but we hope to be in the house for at least 20 years and it will be worth it not to have my DH complain about the hvac! The ducted VRF system is very quiet, so that is a positive.

We tried to hire one of the companies that does the VRF systems for Matt Risinger (video linked a few posts up), to do the original hvac design for us, but they really weren't interested as we are not in their geographic area.

My main point is that most hvac systems have been designed the same way for the last 40 years and you really have to look for someone that is current with new technology ... and knows how to design it properly. Good luck!

Since you mention radiators, are you heating with hydronic radiant? Or are the radiators actually electric baseboard? I can't find where you said what type of heat you are using.

Two things cause noise in forced air HVAC system - undersized ductwork and cheap, builder-grade, single stage systems. Make sure the ductwork is calculated correctly using the Manual D system and get a 2 stage or inverter/modulating system. Forget zoning - 99.9% of HVAC contractors haven't got a clue how to install them - get two separate systems (one up, one down). Of course, these are more expensive but built into a whole house reno, the cost will likely be dwarfed by everything else.

The best time to design a HVAC system is in the design phase--not during construction when order lead times may constrain the design. That said, you are where you are. I would ask the builder what the strategy is for each letter in the abbreviation HVAC:

What is the strategy for heating my home and how did you arrive at that?

What is the strategy for ventilation and how did you arrive at that?

What is the strategy for air conditioning and how did you arrive at that?

Assuming you get blank stares from the builder, ask to speak with the HVAC designer personally. Then repeat the questions. Ask to see the ACCA manual J, S, D, and T calculations. If you get push back or blank stares that would be a big cause for concern. Good HVAC systems start with good design. Good designs are the product of good designers.

Thanks everyone for the input. I wish I had jumped on this a bit sooner, but I now know at least a bit more than I did. I appreciate everyone'd helpful feedback!

Agree with all the above on Manual J and S and addressing all this in the design stage. Ensure they're not fudging numbers or using "rules of thumb" (if it works out to 500sqft/ton or thereabouts, they likely didn't do the calculation).

We had load calcs done on our house by 3 contractors. One came up with 6.5 tons, the other 2.5 tons, the third 4 tons. The 6.5 tons one was clearly just fudged/used a rule of thumb. Our builder would have gone with it had I not asked/researched the types of questions you're asking, so good on you!

A few things that came up in our build I wished I'd known earlier -- ask to lay out the supply/return registers ahead of time so you can plan around furniture and such, and also the size of the returns -- if you want 4" thick filters, make sure they know and plan for that, and also make sure that the size of the returns match commonly available filters vs having to special order them. Return size can affect noise as well, if too small.

Also on returns - good to understand if they'll do dedicated returns in each bedrooms, transfer grilles, or jumper ducts. Make sure the system will stay balanced when the door is closed.

I would say that excess noise is from undersized ducts and returns. Full stop. It is just that a 2 stage system compensates a bit for it. I purposely did single stage equipment for simplicity and cheap replacement. Humidity is not a problem with a tight house and proper sizing.

"Humidity is not a problem with a tight house and proper sizing." I'm not trying to pick on you, David, but such a blanket statement isn't likely to hold true for all homes nor all climate zones. Indeed, homes with extremely low air infiltration (i.e. "tight" homes) can have indoor relative humidity issues, particularly if air conditioning is the sole means of dehumidification and it's outside the normal air conditioning season. Designing for proper ventilation and dehumidification are particularly important for tightly constructed homes.

I agree that a properly sized single-stage air conditioner can be perfectly adequate for many applications, depending on the home's construction and climate zone. I live in a mixed-humid climate zone. I have a single-stage system for the 1st floor and a two-stage VS unit for the 2nd floor of my home (where control of relative humidity is more demanding.)