extending ductwork from crawl to slab

I would like to turn our screened-in porch into an interior space. The house is on a crawl space. The porch is on a slab. Is it possible to extend the ductwork from the crawlspace into the walls of the porch area and have the registers on the walls?

Possible, yes. But HVAC systems are balanced to some extent; adding registers willy nilly could affect airflow in the rest of the house. Also, a screened porch (I'm assuming) is 3-sides open, which means you need a decent amount of registers to be effective. Further, you might need an airflow return if the doors can close.

The point is, don't assume it's as simple as adding a register or two. Have an HVAC man come and estimate what needs to be done.

Thanks for the response. The porch is only screened from one side. The other two sides are presently occupied by exterior grade sliding glass doors, one into a bedroom, the other into the dining room. The plan would be to remove both sliders, but replace the one to the bedroom with a nice interior grade French door.