Can't see what this could possibly be, unless it's an odd way of sahing "insulated" (wood with bonded insulation???) or they are thinking "autoclavé", which would be "pressure-treated".

L‘autoclavage rend le bois d‘épicéa. et de sapin indigène plus durable, de sorte qu‘il peut. aussi être utilisé pour des sollicitations extrêmes. ...
www.flumroc.ch/txtfranz/pdf/aussenwand_f.pdf -

--------------------------------------------------
Note added at 9 hrs (2007-04-22 22:41:55 GMT)
--------------------------------------------------

Does the word appear just the once, despite the many applications of the products, or is it repeated?

It's far from an obvious misreading of handwriting (does anyone actually do that any more?), but is not impossible (nothing is!):
thermostaté
aut oclavé
I can certainly see a badly written "cl" being read as "st", and even a "v" as "t", but the beginning is less obvious.

--------------------------------------------------
Note added at 9 hrs (2007-04-22 22:47:14 GMT)
--------------------------------------------------

One thing I would say, and I mean no offence to people of the countries concerned, is that I HAVE in the last year or two observed a growing number of peculiar mistakes of this ilk (if this is indeed the problem), quite possibly with the growing numbers of eastern European technicians, engineers, etc. working in this country. In my case, I know certain authors to have been from such places. They are not the only ones, for I have also found myself scratching my head over the French written by Swedes and Finns working for French companies. Mostly they use anglicisms though, not the wrong word entirely. But nothing is impossible ...

--------------------------------------------------
Note added at 9 hrs (2007-04-22 22:50:48 GMT)
--------------------------------------------------

It is possible too that handwritten documents have been typed up in a foreign country where people a) don't have the author at hand to decipher things for them, and b) aren't necessarily as "au fait" with the language as one might expect of someone living in France. I know a colleague of ours, for example, who has faxed or handwritten documents typed up in Madagascar before running them through Trados ...