I am replacing vinyl siding that was installed over old wood dutch-lap siding. Currently there is 1/4 rigid foam installed over the wood siding, which I imagine is needed for creating a flat nailing surface. There is no house wrap installed, and someone I talked to said this is fine, since the foam is doing the job of the wrap. He says I should replace the foam and make sure to tape the seams, and this will be adequate as my WRB. Does that sound correct, or do I need to install wrap between the wood siding and foam? Another option might be to use insulated siding, which would negate the need for the foam board, but this kind of siding is much more expensive. FYI, we are absolutely not removing the old siding! Thanks for your input.
Housewrap (i.e. Tyvek and similar products) and rigid foam are in no way the same thing nor do they serve the same purpose.
Rigid foam is an insulation product and does just that, insulates. It provides additional R-value beyond insulation you might put between your studs.
Housewrap is a moisture barrier. It prevents liquid water from entering and wetting your insulation while at the same time allowing water vapor to escape from inside the wall.
Generally you will use both and you might see the requirement for both in your local building codes.