Before Vinyl Siding: Rip-off shingles, or go over them??
First off - the house is a 100yr old 2-story, and has stained wood shingles (not sure if they are original, but they are in fairly poor shape - dry, brittle, and had curled (at some point the bottom of the shingles were nailed down to stop the curl). The house has about ~3,000 sq ft of surface area.
I had two separate vinyl siding contractors come do a consulation. The first guy brought a pretty nice looking Alside insulated siding product called Prodigy. It's backed with 1" of styrofoam (R5 value), comes in long lengths (16'), and has a very realistic textured. He said the only way to do it right was to have all the existing shingles ripped-off, wrap the house with breathable Tyvek, and then install the new siding. He quoted the job at $24k (including the all the aluminum trim, etc.).
The second guy brought a somewhat less attractive Certain Teed product called Monogram 46. It did not have any insulated backing (he called that a gimmick). It also came in 16' lengths though. He said it was actually unnecessary to stip all the old shingles off, and instead proposed to cover them up flat with a foam board, and then install the siding ontop of the board. He quoted the job at $16k, including all aluminum trim, etc.
Does anyone know if it's really necessary to strip-off all the old shingles before installing the siding? There does not appear to be any water damage issues with the existing old shingles, however the first guy said it's important get the old shingles off to avoid any issues with moisture or mold underneath the new siding. The second guy said any moisture under the siding would evaporate when the sun hits the house (of course, the north side doesn't see much sun)...
Also any opinions on an insulated siding vs. non-insulated. The house right now has no insulation, and is located in the Boston area. Some walls will be insulated from the inside during interior renovations, and we may get blown-in at some point.
Thanks in advance to those of you with vinyl siding experience!