Roof insulation vs Ceiling insulation? Both?

Currently the ceiling of my house is insulated (2x8’s with R19 fiberglass) with OSB on top of it. My roof has no insulation in it and my upstairs HVAC system is in the attic. I am in zone 4 in the US which means I should have a min R-value of 38 in the ceiling. I am planning on adding collar ties around 8ft up in the attic and insulating the rafters with r19 with vent baffles behind it. Then on top the collar ties using r19 + r30. I also plan on leaving the insulation in the ceiling.

I am wondering if anyone with sense has had this scenario and then added insulation to the roof. And have actual energy usage data for before and after?

Hi, although I do not have your specific set up at my house I can tell you that we added a lot of insulation to our attic about 9 years ago and it made a tremendous difference in lowering our energy costs. In fact, it was more than just adding insulation. It was using spray foam to encapsulate the entire attic and make it a partially conditioned space. The result has been really amazing.

So I would say if you spend money on insulation you will definitely recap the money on energy savings, especially as energy is getting more expensive. As a reference, I live in Atlanta Georgia. So high summer cooling costs.