I think SIPS are considered the ultimate sheathing for timber frame construction, by the timber framers. Since they can be non structural in nature, you can order them with drywall or some other interior skins in lieu of the osb. (Or in addition to the osb, if you wish). They also do not have to be 'certified' as structural panels, which could reduce the cost of these panels. I know that General Panels' Johnson City TN plant specializes in this type of panel. Contact Butch Johnson for more information on the options available. ([email protected] or 423-747-8710).

John,

Here's another option to consider. You can use the SIP's as the structural component of you building and use other wood to make the timber frame look. Now you can have the timber frame look, an excellent insulated shell, and I think it will be better insulated and less expensive than clading a timber frame.

Steve
GrandCountySIPs.com

I have worked with a company called Ray-core (www.raycore.com) that may help with some of your obstacles. They manufactures a SIP that integrates studs into the panel so you get awesome structural strength will getting a R-42 on 2x6 walls.  Their website says that you can get R-52 out of a 2x8 panel, but I have not used the 2x8 myself, at least not up to this point. I realize support is not your biggest concern, so maybe that can do studs on 24" centers or possibly 48" on center. From my understanding of their product, the less studs you use, the greater the increase in R value.

These panels would also solve your problem about delamination because they do not laminate like a traditional SIP, they inject the foam while in a press so there is no chance of delamination, as opposed to gluing foam to OSB. They come pre-wrapped in reflective vapor barrier so thay is also going to give you a bonus.

Check them out, it worked great for me and I think it would help with several of your issues. They are easy to work with and will help give you ideas without any obligation.

Good luck

Hi, I am looking for more information on raycore panels. I see you have used them do you mind telling me what part of the country you are in and maybe how to find a builder that knows how to use the raycore product? thanks for the info.

raycore is not a true SIP, it is a insulated prefabricated wall assembly. Simply studs and insulation

The shell is still structural as a cladding spanning between timbers, so SIPs are a good choice. If you want a wood frame structure to last 'for posterity', provide a high quality 'sacrificial' sheathing layer over the SIPs, then apply the weather resisting finish over that.