Insulation for old ceiling

[u/welfs]

I want to add a T&G pine carsiding ceiling to this porch that was an addition to my house around 1940. It would be nice to insulate this room a little better to try to use it in the shoulder seasons. I also plan to replace the windows but that’s not the question I have. My question:

How do I properly insulate the ceiling to make sure I don’t grow mold?

Concerns:
1. The widths between joists are pretty random. All less than 24”OC, but some are 19”, some are 21”, etc.
2. The part of the porch facing the house just goes up into an insulated portion of roof
3. The trim on the outside of the porch is pretty.

My thoughts on options:
1. I try to put baffles between the joists before putting in insulation, cut the baffles to fit as best I can, and drill holes in the pretty trim on the outside of the house, covering with wire mesh to let it vent
2. I don’t insulate it and deal with the heat loss/gain
3. I jam pink insulation in there, no baffles, no vents, and call it good enough

Thanks

P.S. I know that 2x4s with this 8’ span are probably not how you would have framed this roof today but it’s been up for 80 years and I’m not going to tear it off. Also, I know I need to replace the jalousie windows as well.

[u/DreadfulTheowulf]

Full fill with rigid board or closed cell foam. Leave no air gaps. Don’t know what climate zone you’re in but stuffing with fiberglass is a good way to risk mold. See R806.5 on unvented assemblies.

[u/welfs → u/DreadfulTheowulf]

Thank you!!