It is best to have all duct work and equipment installed in conditioned space. Duct work in an unconditioned attic is the worst place in my opinion.

Yes, Mike is correct. But it also depends on the type of system and equipment you may have, and what's feasible based in house design.

FWIW, distribution and return ducts are generally too large to be placed in walls. That's why they tend to be in attic space or in furred spaces below second floor framing.

Hard to generalize, since so much depends on house design, and type of system.

The duct work for my 36 year old two story house is in the walls and floors. There is a furnace for each floor. Both furnaces and coils are located in the basement. It can be done, but it has to be planned as part of the the house design.

Sound like you are talking about heating, and you have a basement, not SOG.

I'd wager your risers for the second floor are in a furred chase and not in 2X4 stud space.

I have split systems, so it is heating and cooling. The supplies and the returns are in 2 X 4 walls. The main duct work runs are in the basement.

My previous house was two story built on a slab. The furnace and coil were in a closet next to the kitchen. The duct work was in the first floor ceiling then ran up or down to registers in the wall near the floor.

Every house is different, primarily due to system components and installer's experience and preferences.

For the OP, tell us your location and type of system.

im in SC. Builder will be installing heat pump system .– 15 SEER Hi-Efficiency HVAC Unit

– Digital & Programmable Thermostat

– Certified Manual D Duct Design

Certified by whom?

Heat pumps come in a variety of configurations, but generally consist of a condenser unit (exterior) and a separate air handling unit (interior). The best solution is for the air handling unit and ducts to be in conditioned space.

It's often the case that supply and return ducts tend to be large rounds, with branches for individual rooms.

If you have an attic or basement, they tend to be the most economical areas for the supply and return ducts to be located, with registers in ceiling or floor.

If you have more than one occupied floor it gets more complicated.

Unconditioned attics are probably the worst place of HVAC ductwork. Nevertheless, its the most common way to run ductwork in multi level homes (and a lot of single level homes). Most codes require a minimum of R8 insulation, but you can always use more.

I like conditioned attics, but the cost to construct them is a function of the roof area. If your home is on a slab, I'm assuming it's a single level home which makes for a larger roof area than a straight-up two-story design. Cha-ching.

In lieu of constructing a conditioned attic, you could create an insulated enclosure for the ductwork within the attic (essentially incorporating it in conditioned space) or run it in soffits under the main ceiling.

Alternatively, you could ditch the ductwork altogether and install a multi-zone ductless mini split system. They are extremely efficient, quiet, easy to install and are easy to zone compared with conventional systems.

With either approach I recommend supplemental dehumidification and fresh air make up systems.

The other option is to build a utility closet to house the HVAC equipment. Less expensive than building an conditioned room in the attic and makes access for servicing easier. The down side it it takes up some living space.

Installing ductless mini splits can become expensive for a two story house with four bedrooms. Then you have the problem of multiple supply heads throughout the house. Right now natural gas is very cheap in the northeast. This makes heating with a natural gas furnace less expensive than a mini split.

@Mike,

The OP indicates that the home is in SC which is a humid/subtropical climate. For a humid/subtropical climate, air conditioning the space is a more important design consideration than heating. No system is perfect, but mini splits are gaining in popularity especially as homes become better air sealed and insulated. The OP should consider all available options so they can make an informed choice.

I fully agree the OP should explore all options. There are many things to consider. For a new home buyer it can become over whelming.

The thing I was always say, most builders know little about HVAC, and will look to spend the least amount of money on equipment and installation. The home buyer needs to do their own research if they want an HVAC system that will work well.

It's sad but true that most home builders know little about HVAC. It's sadder that the same can be said of the majority of architects and residential HVAC contractors. This despite the fact that HVAC is mission critical to the health and comfort of the occupants and the long-term sustainability of the structure.

Unfortunately, the best research in the world by a home buyer isn't worth much if the system is going to be sized and installed by the low-bid contractor a.k.a. Chuck-and-a Truck, Inc. When choosing a home builder, I encourage prospective clients to ask questions about systems like HVAC, plumbing and electrical. If the answers are vague or wandering off topic, keep looking until you find the right builder.

Thanks for all responses....I really appreciate it!