Raising Garage Floor to match House Floor
I would check with your building dept. In my area we are not allowed unaccessible wood framed spaces to raise a floor. Venting would be one of the issues.I have seen it done in other parts of the country.
I'd look into pouring concrete. It would probably require some seperation from any existing wood framing, (walls, joists, etc) and it would be best to find out what is customary and allowed in your area. My area is semi arid so the way i might do it would probably not be allowed in Florida.