Thank you klem1.

What would be the advantages to installing the separate upstairs unit? Note I will probably use the studio upstairs daily and the guest bedroom every other day. (It will double as our gym.)

I have to hope that our builder has qualified installers. This is a fully custom build, so I'm assuming it does.

What are your thoughts as to the actual equipment assuming it's installed by experienced people?

Personally for me, one of the things I hate most is how most units get cold, shut off and then the room heats up, and the process is repeated. I'm constantly putting on and taking off my sweater in our rental.

I will address your last question first. Large temperature swing is more common during heat mode due to improper t-stat calibration. Non-zoned in cool mode I can only guess but on site evaluation will easily find the cause. The combination of poor insulation,drafty windows/doors and wrong location of t-stat can swing temperature excessivly. This is one of many possible issues with improperly installed zoned equipment. It isn't something that must be tolerated. Balancing temperature between 1st and 2nd floor is doable but challenging so having a separate unit upstairs take's that off the table. It can be beneficial having part of home comfortable while waiting on repair during summer heat of SW FL. Not the case with you but ability to have guest room ac stand idle during long periods of non-use save's energy as well as wear and tear on unit. This is only speculation but electric suppliers may soon control power to havc equipment during peaks of high usage. Many areas are already doing it. My friends in AZ tell me their secoundary ac is exempted by power company so that might prove valuable if it is the norm. Since you are not able to choose hvac contractor,I suggest the "squeaking wheel get's the grease appraoch". That is to say telling the GC in a firm but bussiness like way you insist the hvac been done as well as possible or you will be a thorn in his side until it's right. We hear people saying their GC want's them to work out problems directly with hvac sub,let GC know you will not down that road. So far as comparing equipment,I'm retired and not in the game daily.

Thank you klem. Good info.

The Carrier FV4CNF005 air handler has a variable speed blower, so I don't understand the additional $3150 upgrade. Is this for an Infinity air handler? You need to get the model information to make a decision.

You have to decide whether you need to spend an extra $900 on WiFi thermostats. This would allow you to change the temperature when you are not home.

Get the model number of the air cleaner. You are better off getting a 4 inch media filter instead of an electronic air cleaner in my opinion.

"I have to hope that our builder has qualified installers. This is a fully custom build, so I'm assuming it does."

Don't assume anything. Find out who is the HVAC subcontractor and see if he has a good reputation.

I realize this is Florida, but what are you doing about heating?

The condenser the OP listed is a heat pump. So heating will be done via the reverse cycle of the AC with emergency strip heat for those rare times that Florida dips under 32 degrees.

Florida can be a humid place for extended periods. If you just merely add a variable speed air handler the amount of dehumidification you get isn't much.

My advice would be to have them quote a 2 speed heat pump with the variable speed air handler. This will give you much better dehumidification. This can also alleviate those hot to cold swings, because the system runs longer due to having two stages. Which more or less equals less cycling on and off.

If you opt for the 2 speed equipment with variable speed air handler you should pare this equipment with a communicating thermostat from carrier to match this equipment. Carrier Communicating Thermostats

Above this installation is everything as already stated.

I'd be happy with heat pump option. here in hot humid Louisiana

where winters are/can be mild, heat pumps are excellent choices.

In my existing home I maintain 52-55% relative humidity

with properly sized, designed & installed heat pump and

variable speed air handler.

while I do have a whole house dehumidifier, I only use/need it

during shoulder seasons when minimal a/c is needed.

upstairs rooms could be mini split unit with two heads.

what type construction? stick build, concrete block...

what type insulation package have you opted for?

where are ducts located (in attic??)?

invest in a load calc for the house, with a duct sizing & design.

avoid companies that will try to install 2 ton system on 800 sq ft

upstairs.and definitely avoid companies using rule of thumb

sizing (400-500 sq ft per ton).

best of luck

Thank you Mike, Austin and Energy.

what type construction? stick build, concrete block...

Stick upstairs and concrete block downstairs.

what type insulation package have you opted for?

Closed cell spray foam in the attic. And I forgot the rest. LOL. Blower test is required here in FL too.

where are ducts located (in attic??)?

I believe so, but will double check.

invest in a load calc for the house, with a duct sizing & design.

That was definitely done.

Make the ducts inside the house if you can. Ducts leak and that turns your air handler into a power vent.

Why do you want zoning? If it is necessary for comfort, go for it. If it is for energy savings, think about it. In a modern, well-insulated and well-sealed home, the heat transfer between rooms is much faster than to outside the home's envelope.

I want zoning because I like it cooler upstairs than my DH does downstairs. Also my new house is a U shaped house with the master suite on one part of the U so why should I cool that room all day (especially with it on a west wall) if I don't need to? I need it cool only at night.

If zoning is done right it is the cat's meow for comfort... especially for a hot humid climate... in a U shaped home it's also a good way to alleviate trouble spots. All to often I see these kinds of layouts the master is way over on the other side of the house from the thermostat and people wonder why they aren't comfortable?

So there's much more too it than efficiency with this type of home floor plan. With zoning involved I would even more encourage you to select a two speed Heat pump even if it means having to ditch the communicating thermostats.

A zoned system will work much better with a 2 speed system.

Having lived in Texas for many years (hot, but drier than where you are), on new construction I would always opt for separate A/C units for 1st and 2nd floor. It is very hard to keep upper/lower floor balance when you use a single system. Keeping it balanced by zoning with the ducts may be possible, but I think it will be hard to find an A/C contractor who really has the skill to make that work. Another bonus is that when you have two units it also gives you one working system if the other one goes out at a bad time.

For the upper floor they will probably plan for ducts in the attic, which is not optimal because they are exposed to heat/cold. However, if you can't get the ducts within the conditioned envelope, at least make sure they use well-sealed hard ducting as much as possible, preferably metal ducting with insulation over it. A heat pump runs a lot and you want the air to flow well. They will probably want to use big flexible ducts (like a slinky), which really reduce air flow compared to smooth ducting. They may also want build some of the large plenums with duct board, which is better than flexible duct but not as well as nice smooth metal ducts.

Also make sure they put a cold air return in each bedroom and one on the top and bottom floors in the main part of the house. You want air to flow to/from every bedroom even if the door is closed.

Bruce

Dividing the load between two systems also makes it easier to say comfortable in a power outage with less generator capacity. I think inverter-driven compressors help too.

Thank you all. We meet with the HVAC guys this week so will work out the final details. All the info has been a tremendous help