You need to talk to your HVAC person we have no idea what your actual needs are

I can also ask here and see if there are any HVAC professionals with general advice from dealing with similar situations.

Generally the best location for a furnace is low and in the center. Any variation from that and you will lose efficiency. The furnace can go anywhere, it just may be more costly in the long run.

("long run" pun intended)

Take Patricia's advice.

Is your priority heat or A/C? A/C in the attic works relatively well because the cooler air drops naturally, and the fan is on a higher speed with A/C, but forcing heat down is a little more difficult.

If you do put them in the attic, I highly recommend making the attic conditioned space (they will foam insulate the roof and the attic is unvented).

Bruce

@Bruce in Northern Virginia thanks. The A/C is definitely used longer but we are in N.C. so get a fair bit of use out of our furnace but average temps are always over freezing. The A/C units for beside the house but maybe there’s something in relationship to the furnace you are referring to. We will insulate the space up there. It’s standard here to put the upper floor’ unit in the attic, but usually the main floor goes in the garage as there is no basement although some do have mechanical rooms. Thanks for the feedback!

@Seabornman coastal NC! Thanks appreciate the feedback! We are just in design phase and was looking for some hope. We could turn our pantry into a mechanical room if absolutely necessary, but that’s not fun, so hoping there will be other options.

Just a thing - a furnace is generally used when you have gas. You will have a heatpump. We have a place on Topsail and our lower floor heatpump is hanging under the house. We are on pilings and have parking under the house. The house is 45 feet wide or so. Parking is for 2 cars so this area is in between. We are at 13 above sea level which is our BFE so the unit is comfortably above flood area.

Our upstairs unit is in a closet.

All of this should have been planned well before permitting. How far along are you?

Unrelated advice - foam and seal the roof - the hurricanes drive water through the soffits.

We are still designing the house, not anywhere near permitting yet, we just don’t have a lot of extra space with the plan I’ve sketched up And the designer is now working on. We have a piling house now and I’m tired of living upstairs so we are doing a raised slab this time around.

So this is what I have confirmed.

"Coastal NC" "on Island"

Now, where can you do a raised slab in this setting? Emerald?

What is your ground elevation and your BFE? If your elevation is anything below 20, then you better learn what BFE is.

Real world example. Colleague with a 70s shack (1200 ft ranch redone very well). $13k flood.

My house - 2100 sqft, built in 2010. $3k flood.

If you are thinking a raised slab - you need to clarify what that really means to me. I have a slight slope inland and we did a monolithic slab which is really just a thick slab in some areas. Is that what you mean?

Now if you are up on a hill, why not just build on a crawl and put mechanicals there?

Putting an air handler which serves the first floor in the attic of a two-story home will require space to run the main supply and main return ducts to/from the attic to the first floor, respectively. You need to sit down with your designer/architect and HVAC designer early in the design process to make sure you've allocated sufficient space.

You've indicated that space is at a premium in the home. I suggest you consider using ductless mini-splits in lieu of a forced-air system. We rented a home on Ocracoke Island a few years ago which was conditioned by three mini-split wall units. It was extremely comfortable and the wall units allowed the conditions in each bedroom to be set according to the occupant's preference.

Are there any pros here that know if a furnace for the first floor in a two story house can go in the attic?

Yes, see this all the time here in Texas. Homes are built on slabs here nearly 100% because we're at sea level.

You will need proper sized return, my preference would be at least 2 especially if the master bedroom is on that lower level.

You can condition the attic, but these kinds of ideas can become problematic as the house ages, needs roof replaced at some point. A well vented attic with natural venting has been proven to work. If it were me, that is what I would focus on for HVAC equipment that is placed in the attic.

Not only do you need return spacing, you also need spacing for supply ducts to each and every room on that lower level.

It is in your best interest to get an HVAC system design specialist to figure this out. There will likely be alot of HVAC companies that will tell you no... they don't get involved in new construction.

So realize you are looking for a 'specialty'... your builder should be able to help you with this.

We have a high attic. Can the two furnaces both go up there and run duct work down to first with a shaft?

The answer is yes. Installing HVAC in the attic is not the ideal location especially if the duct work has to travel one floor below. However it can be done if the builder and architect plan the space for adequately sized and positioned duct work.

@David Cary I’ve lived here through Michael, Florence, Dorian and several TS. We know where are new lot is elevated to and it is not in a flood zone. I don’t like to give out my exact location on a public forum. We already own a home here and are full timers. Many ranches built around it but ours will be elevated 2’. Not a monolithic slab but a stem wall foundation with slab. The plans will be sent to an engineer after being drawn as we are having it built to for the fortified gold standards by a very experienced builder.

Obviously they will find the locations for the HVAC system, but I wanted to have suggestions since I drew the floor plan sketches first and the garage was attached so it wasn’t an issue. We’ve since changed the plan a bit and detached the garage and now we’ll have to figure out where to fit it in! I of course am hoping to not mess up what I have envisioned for our home So was hoping the attic could be an option!

@Charles Ross Homes thanks for the idea. We actually have a mini split in this home as we added a family room and conditioned a previously unconditioned space. It works well, but it is not the look I prefer for a higher end brand new build!

Some of the mini-splits now offer a ceiling cassette that will look very similar to a standard ceiling vent (in place of the indoor unit on the wall). This is one example.

https://www.ecomfort.com/stories/1319-How-to-Pick-the-Perfect-Mini-Split-Ceiling-Cassette-Unit.html

Bruce