Hi. Since no one else has replied yet I'll offer my 2 cents from my experience with my old house. I would call a few companies that do insulation, have them come out and give you a quote on their recommendation. Ask a lot of questions. Find out order of operations. And if they make you feel at all stupid, don't work with them. A question: is there an air duct for heating/ cooling? If not you may need a mini split or similar. Thats pricey but obviously necessary. And again get the order of operations right so you don't waste money. Good luck!

Me again. Can't find a way to edit my previous comment. We did this exact thing with a back porch. Windows look older - we replaced ours, made a world of difference. This is not a straightforward thing and if you ask a roofer all you'll get is information on roofing. You need a general contractor who can understand the job comprehensivly and help you create a plan.

There are many factors to consider.... How cold are your winters? Does the porch have any source of heat or ability to add it? Is it sitting over a basement or crawlspace?

Fiberglass insulation would be the least expensive, just make sure it fills your wall cavity. R13 or R15 for 2x4, R19 or R21 for 2x6. Since you have so much window area and you don't mention insulating the ceiling keep your expectations modest, it will help you towards your goal.

How much four season do you need? What will it be used for? Also, how much heating would it need in winter? Would you want any summer cooling or would windows open be enough?

I use my enclosed porch year round. I don't heat or cool it. It has great south face so gets solar a lot. It does get around freezing in the winter, but it stays several degrees warmer than outside and I can overwinter plants out there. Windows open in the summer. It has ceiling fans, I don't like to use them they are old and meh. It gets pretty darn hot during the dog days. We don't hang out/living space out there much. It's mostly a utility/gardening sort of thing.