1. Ask a local HVAC person.

2. Ask a local HVAC person.

3. Ask a local HVAC person.

Thanks Mark.

I know it may not seem very helpful, but it is the way to get the best results.

We have a house this size in Maine....with 6 zones...we have a townhouse in CO half this size...with 5 zones.
All depends on what you are heating and how you want to do hat.

A 2-story house 4000 sq. foot house needs two HVAC systems. I suggest one system for the second floor, and the one for the first floor and basement. You could makes zones for the first floor and basement. The heating load for the basement will be small, and the cooling load will be virtually zero.

The first floor air handler could be installed in the basement. The one for the second floor could be installed in a second floor utility closed. I don't like HVAC equipment installed in unconditioned attics. If a utility closed is not feasible then I would install both systems in the basement.

If the funds allow I would recommend 2-stage heat pumps with variable speed air handlers. The current rule is 14 SEER is the minimum for Maryland. Variable speed and 2-stage equipment usually has a 16 SEER rating which is a good compromise in installation and operating costs.

The installer must do load and duct sizing calculations. If the contractor wants to use rules of thumb then get another contractor.

We have 4500 square feet above grade plus a 1000 square foot finished basement. We have 4 zones total.

What zone are you in? How much heating, cooling and humidity? It may be well worth it to get better windows, especially if there are a lot of them, and focus on insulation. Electricity can be a very expensive way to heat (& cool).

Have you looked at a ground-source heat pump?

If it were me, I would do 3 zones as a minimum. The basement needs will be minimal, depending on your layout and how far below ground you're talking about.

On a new build, I wouldn't go less than 16 SEER. I would do variable blowers and multi-stage, except for the basement perhaps.

Since this is a new build, I would invest in R25 walls (or more), good roof insulation (r50 or more), good air sealing and good windows/doors. The heating/cooling loads will come from the plans. Same for the ducting (Manual D).

I did 15 SEER and am completely happy. There isn't really that much difference. Spend your money on insulation.

I would do 3 zones. The basement needs no a/c - just some dehumidification. But needs heat when other zones don't. You can do a single unit on the first floor/basement and zone it. Or you can do 3 zones. Zoning is hard and dependent on local experience. So I would go back to what Mark said....

Variable speed is nice. I don't find it necessary on a well designed system. But that is a big question.

Mark, I took your advice and spoke to several local HVAC guys.

In one day. I like the way you work!

All the rectangular two-storey plus finished basement 2,400-4,400 sf homes I've built were well handled by a single furnace and central air unit in Climate Zone 5. A multi-billionaire family I know of--but sadly am not married into--had seven or eight zones in no more than 5,000 sf.

Multi-stage equipment is more about comfort than operating cost savings. You have to decide how much the comfort is worth to you. The maintenance costs are the same. Compressor repair would be more expensive.

A variable speed air handler is going to of minimum value if the heat pump is single stage.

LPG maybe a good option too.

I would install 2-stage HP & variable speed fan coils. That basement will require heat when other zones don’t and will likely require dehumidification during the summer.

I would also very strongly suggest subcontracting the HVAC - including the ductwork yourself and take that aspect of the build out of the hands of the General Contractor.

New build, that many square feet, no NG? I would at least look into geothermal!

IMPO

SR