I would like to start off by saying this forum has been an invaluable resource over the past several months as I've embarked on having an entire new HVAC system installed in my 1950's ranch.

The system is supposed to be installed soon and I'm seeking expert feedback on a few outstanding issues I need to address with the contractor.

New equipment

- Trane XL15i heat pump w/ 15kw heat strips (2.5 tons)
- Trane TAM7 air handler (3 ton)

Space:

- First floor and basement (985sq per level)
- All new ductwork is to be installed in the unfinished basement to keep it inside the building envelope. Previous system being replaced had all A/C ductwork the attic with separate oil boiler / hot water baseboard heat.

As per my research, I had a complete independent Manual J, S & D done on the home so I could have something to compare to any quotes I received. At this point a have selected a contractor and the install is approaching.

A few questions:

1) I'm insisting on a Manual J, S and complete D from the contractor prior to installation so I can review a blueprint / design prior to any ductwork being installed. I really don't want something designed on the fly. Is this acceptable?

2) I would like to have a supply under each window on outside walls for the "washing" effect. I'm pushing for 4x10 supply registers (according to my Manual D) under each window in the bedrooms (different walls) as opposed to one larger 8x12 supply contractor suggests. Does this make sense?

3) Returns seem to be the big issue. There's plenty of room to run individual returns in each room/space either in the floor or low wall. I'm being told this isn't possible or optimal in an older home and a central return in both the basement and first floor is the only route. Contractor also added that no return is required in the bedrooms and other rooms even when doors are closed.

Am I being unreasonable to insist on a return in each room or what is the best route? I really don't want to give up either of my small closets to central returns and ductwork.

4) I would like to avoid "joist panning" and prefer to have metal pipe or flex ran on the returns from first floor to trunk. The main idea is to minimize duct leakage and keep building cavities out of the system.

Does this seem acceptable given low wall or floor returns? The return trunk (in basement) is roughly 4 feet away from boots that would be installed.

5) Contractor states that floor returns would lead to dirty/failed coil even though the install will include a central 5" media filter. Is this true?

Wouldn't interior wall floor returns be easier (plaster walls) and be less restrictive over using a small wall cavity for low wall return?

Would low wall or floor return be preferred in MD?

Sorry for the long post! I really appreciate any feedback.