Thanks, Deb.
The building is in Poland. The existing exterior must be re-clad in stone, so the insulation will be between the stone and the existing surface. Heat gain will be lost. Windows are not terribly big. Does it give a better picture?
I thought insulation  poured  into the cavity (vermiculate or styrofoam chips) will do the job. No vapour barrier. Condensation (and any rainwater leaks thru the wall) would be dripping down on the inside face of the stone cladding and would drain out at the bottom of the wall. Ventilation would be provided at the top of the cavity under the roof overhang.
 I'll chat with you in a week or so, leaving for Poland in 1/2 hour.

Peter

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> Hi,
>
> You might want to try prefab aluminum insulated panels, usually sold with
> porcelain finish on one face for a nice exterior appearance, but probably
> available on special order without, and less expensive that way too.   They
> consist of two sheets of aluminum bonded to a closed cell foam--very high R-
> values.
>
> Mapes Industries in Lincoln, Nebraska, USA, is a manufacturer of such.  Since
> the panels are rigid and lightweight, they can be applied in many different
> ways, to suit the substrate, and the substrate doesn't have to be structural
> or the surface sound, although in your case that's probably not an issue.
> :-)   The aluminum is a pretty stable material also, not subject to water
> damage, mold, etc,  as masonite panels are.
>
> The only drawback might be if your building has a lot of rounded components or
> irregular architectural details, like towers and such.  In that case, maybe
> there is a way you could use a flexible membrane/insulation system similar to
> those used in  commercial roofing.  They are usually horizontal and
> ballasted, but you could probably get a manufacturer to engineer the
> application and recommend a different method of  installation.   The key is to
> stick with closed cell foam material so as to get the higher R-values and
> avoid condensation problems down the road.
>
> There is probably some type of spray on product, but I would be reluctant to
> spray anything permanent and gooey on something from the 14th century that ppl
> in the 23rd century might want to restore to it's original condition.   ;)
>
> FYI, from an energy standpoint, you usually _would_ want to insulate the
> outside of any massive masonry structure, as you can better control the
> thermal flywheel effect that way.  When you insulate masonry structures on the
> inside, you can have problems with condensation, deterioration, and mold at
> the interface, and so have to pay quite a bit of attention to installing and
> maintaining a seamless vapor barrior, which is rather difficult to do.  That
> is not such an issue with exterior panels, because the difference in temp is
> not so great from inside to out, once it's been spread out and tempered by all
> that mass.
>
> On the downside, when you insulate a massive structure, you lose any exterior
> passive solar gain benefits you might have had, once you isolate the masonry
> from the sun.  That is not always an issue,  perhaps you have big south facing
> windows and so can trap the gain inside the structure rather than collecting
> through the surface of the building, but something to consider in some
> situations and climates.
>
> Please post updates on the project!
>
> Deb Bledsoe, lurker
> Reily Twp,  Ohio