I'm looking for some information/guidance on a couple of items

First: how early in the home design process should an HVAC install/designer be consulted? Concept, layout, construction doc phase?

Second: I'm hoping to have DX-GSHP system with DSHW and a dehumidifying ventilator in an ICF home with foam on the roof decking. Can anyone recommend someone in my area (Ann Arbor, MI) that is familiar with these systems? Currently I know of only 2 companies that manufacture direct exchange GSHPs- ECR, and AmGeo.....any others?