There are alot of ways to do this. It depends on what type of thermostat, does the t-stat automatically lock out heat or ac when the other is running or do you have to provide for this? Do you have the proper boiler control to allow one boiler to serve two zones? Is the boiler control included? Any extras like air dampers? Carrier, York, Trane, depending on the features built in all get wired a little differently. If you're going to do this, get the installation manuals from all the makers first, get the T-stats that are recommended for the options you have or will install and you'll be able to figure out what to do. Of course, this is one of those areas where you'll spend three days doing what the HVAC guy could do in a morning. I'd let the GC hand this over to his heating contractor.
