Return ducting for refrigerated air conditioning

[Homebuilder]

I am new to this group and don't know if a residential air conditioning question is apropriate or not, as it has more to do with ventilation than cooling, but here goes.

I am finishing up my new home construction plans with my architect and an HVAC installer has told me that I do not need return air ducting for my home cooling system.
So, I am confused as to whether return air ducts are a necessry or good idea. I plan to use a factory built system that uses an underground buried condensor coil system for ground heat exchange, utilizing a closed loop refrigerant that couples to an outside unit most likely using an expansion valve to the cooling coils and delivers the cooled air with a fan into floor ducting via the crawl space in my design for a one floor home. The home construction has high ceilings and no dry wall, using instead, beam construction on celular concrete block walls with a clear story series of operable awning style windows for indirect natural lighting and exhausting heat in the summer time if necessary.

The heating system will be a hydronic floor system so there won't be any forced air heat in the home and therefore the ducting will be exclusively for cooling, entering each living space via floor registers.

So, in order to allow for an adequate and healthy turn over of air flow, I am wondering whether to exhaust all cooled air to the outside of the home or allow passive return to a return air plenum to be aportioned for balancing the air volume between outside exhaust vs. recirculation back across the evaporator coils. I think that a generous portion of recirculated return air would make the system more efficient. The system also incorporates an adjustable humidifier for the supply air.

If, alternatively, one were to choose a heat pump system for "both forced air heating and cooling", would I not have a return air plenum used for both cooling and heating? Any expert opinions?

[Tesla]

Hi Homebuilder and welcome to our forum.
In regard to return air - I would be getting not less than three air con contractors advice/prices. For an efficient system which will work you will need return air in some form. For cooling mode supply is best supplied from the roof. You could still provide full fresh air with a plenum designed for an AHU including a spill/exhaust damper. To so this for optimum quality and efficiency use a pressure sensor to maintain a slight positive pressure on the inside. Invest in a good controller that do it all with room for a little expansion in the future. With VSDs and VRV you can get the best but choose wisely for an experienced person to set it up and design it. If you want the very latest in technology and can afford the capitol a chilled beam system with VAV is best but not many of us know how to set it up for a domestic application, mainly used on commercial buildings.

[Magoo]

Hi Home builder.
I totally agree with Tesla.
A one up capital investment will pay back real quick in efficiency. Insulate the R/air ducting.