Also posted to another forum... Tackling another neighbors vinyl siding job and we see the sub is 1/2" fiberboard underneath Masonite siding. Research makes fiberboard seem like a good sheathing material in that it has (to some extent) both sound deadening and insulation properties. What I'm wondering is if the sheathing is still solid are there any negatives to continuing its use under the new vinyl siding? Secondly, just got back from The Roof Center and found they now carry Certainteed CertaWrap. As it looks to have been released as recently as Q4 of last year I can find no reviews (neither tech nor practical). Anyone had a chance to use it? Looks very much like Tyvek but has a nice loose filament (fiberglassy) backing that should do well in keeping it just off the surface of the sheathing. A 9'x150' bolt sold for $150. Certainteed CertaWrap Brochure (Upon additional research I see Certainteed trademarked "CertaWrap" on 7/19/2011 but I also find older documentation that talks about "Typar HouseWrap/CertaWrap". Was Typar maybe acquired by Certainteed and this housewrap is really nothing "new"?) Typar HouseWrap/Certawrap NRC Evaluation Cheers!