I am going to go in depth on how i have researched out HVAC for my residential house:

there are like 5 systems that are often used in combination or on their own:

• fans (recirculate within a room or can be in the top of a house window to make negative pressure, so every open window has a breeze) (most houses have vent fans to make negative pressure in the microwave or the bathroom, but newer houses are not generally made to handle negative pressure well)
• swamp coolers (water + surface area and fans) (these are the cheapest way to cool a house, but you have to vent the humid air out, so it will only get “so cold”) (these can use the centralized air ducts or be a portable room unit) In my opinion, every dull man in this club needs to have a portable unit blowing on you in the summer while working in the garage because cool humid air flow feels like it makes me twice as productive to the alternative (sweating and trying to make decisions while heat exhausted)
• electric room heaters (these can be centralized via baseboard/wall heaters or as a portable room unit). I think every person in this dull men’s club should have one incase your primary heating system goes down or your damn bathroom doesn’t heat as fast as you like while you are showering in the winter. It is faster and cheaper to heat air with a portable room unit that to heat air with leaving the hot shower on for longer.
• heating oil and a boiler and pump system (you will see a lot of radiators in old houses that have this) There are some portable room units that use electricity for the heat.
• central air conditioning (heat pump and small pipes give cold to the central unit, and propane or electric give heat to the central unit) this is the most common in many places in the USA. It recirculates air, and any fumes (e.g. burned food or poo arisol or bleach fumes) have to be vented outside via a window or other (or in my house, breathed and filtered out using my own lungs). OP’s installation of a 96.5% efficient furnace probably has two plastic “burn” related pipes that both supply fresh air to burn and vents out the low temp but high humidity exhaust. Note that the exhaust MUST HAVE A SLOPE BACK TO THE FURNACE or the exhaust will condensate a blockage in a water belly in the exhaust pipe.
• a minisplit system (heatpump outside with two small pipes to a couple heads that are each controlled by that room’s remote) It can both heat and cool.
• heat/environment recovery vents (HRV or ERV) - these have 4 ducts: a external supply/intake, an external return/exhaust, an internal supply/intake, and an internal return/exhaust. They have a small radiator and fans inside to push the air through the radiator. It doesn’t take much electricity and can run all winter/summer without taxing your electricity much. If you add a heavy filter (e.g. HEPA filter) on the external supply/intake, then your allergies will go down and you will have pretty dang fresh air no matter what is going on.

I personally believe that the ideal house will have 3 HVAC systems built into it:

• minisplit (heads in each room and a unit outside).
• HRV or ERV depending on your region (makes the air fresh and eliminates the need to ever have the bathroom fan on or fuss with the microwave recirculating the air because of crappy installations, and any drying of clothes in a dryer will not have the dust in the house go up.) (this also will keep the air clean if you have a HEPA filter, so any nuclear fallout, wildfire smoke, or pollen wont bother you)
• a swamp cooler (largely unused unless the power went out in the summer and you are running on a generator) (if a karen buys your house from you later, you could easily replace the unit with a central air unit without having to tear out your walls and run new duct work. You could have them run a few copper lines with the “armor” insulation around them so that any future HVAC tech would be able to simply hook it up. Shrug. I am daydreaming about a house built from scratch with me micromanaging its creation.

from a dull men’s club perspective, my ideal house would have a ton of ducts, so i would suggest having “trusses with trunkline holes” designed into them before building any floors. I am currently retrofitting my attic to have a flat truss so the flex ducting can run under my catwalk and be fully insulated without any chance of pinching. Also, sidenote, there is such a thing as “vibration isolators” which are basically rubber or mount-spring-mount devices to put under the feet of a appliance that makes vibration. I strongly suggest spending the 12 bucks to put it under your washer, dryer, and outside AC pumps. You can cut a couple 2x4 scraps to make sure that the proper “spacing” for the washer and dryer are maintained while you tip and put the feet under.

im sleepy. thank you for coming to my ted talk