I am rising our livingroom floor 6". I have a crawl space under the existing that is insulated. Do I need to open up venting between the sunken and raised floor? Do I need to add insulation between the two floors?

No and No. Go ahead with the raising. Xtra insulation won't hurt but is probably not necessary.

If you do add additional insulation, be sure that is is unfaced insulation.

I agree to a certyain extent but you need to tell us if there is a moisture barrier immediately beneath the old sunken floor. If so you can not add more insulation below the new raised floor.

Greetings to you.

I must say not enough information: is your home on a slab foundation, you mention a crawl space
But no materials you are using and do you know the code where you live. If you have a basement it is a different work altogether. Please send more details

The home is built with a footing and a 2 foot 6 inch concrete wall. The floor is 2 x 8 joists with 3/4" floor decking. There is a vapor barrier that lays on the dirt in the crawl space. I do not know the building code.