Insulation, Radiant and Vapor Barriers - insulation under vinyl siding

I have an old house which currently has aluminum siding which is old and filthy and is very cold with many drafts in the winter, my plans are to have the siding removed & replaced with vinyl siding. Most of the estimates I have received include 1/2 inch foam board insulation, is this enough insulation? I reside in nyc where it is very cold in the winter & very hot in the summer. I think i read somewhere that 1/2 inch foam board isn't enough, is this true?
Thanks, any advice would be greatly appreciated.

Find a contractor who installs vinyl siding over ThermoWall insulation. It isn't flat, it's shaped just like the siding! Supports the siding better and has a higher "R" value.

Actually dispite the condition of the siding you alum is a better material, too bad you can't clean and refinish.

If you are going to keep the home a better choice would be steel. It cost more, but is "the best material".

As for the insulation. A much better choice would be a radiant barreier,(foil face paper(or plastic film), both sides, perforated).

Foam is not much better than fiber glass, about 20% efficient. Radiant barrier about 95%. Moisture can form between the foam and wood stucture. Not so with radiant barrier. The radiant barrier will also act as an air infiltration barrier. Foam will not unless unusal care is taken. Some contractoprs claim to have problems installing foil under vynil. I never have. But then I also use drywall screws to attach.

If you or your contractor want more info let me know.

Thank you,