RoofKrete makes thin flexible ferrocement that is also vapor barrier
I recently stumbled across a green builders’ discussion of a product called RoofKrete, which claims to be a form of semi-flexible ferrocement that can be sturdy and self-supporting in shells as thin as a quarter inch. An additive to the cement makes it a vapor barrier as well, rated to last over 100 years and expected to last much longer than that.
The obvious use for RoofKrete, and the major market at which it is currently aimed, is repairing failed flat roofs and constructing long-lasting, low maintenance new ones. But the reason it caught my eye was the potential for green buildings.
For example, you could coat polyurethane with RoofKrete on both sides, because it would flex as the foam expanded and contracted in response to temperature changes, something tough to achieve with conventional concrete. If the product works as claimed — and this really has been deployed in buildings throughout the U.K. — then it does make it comparatively easier to construct insulated buildings without thermal bridges, and without air leaks, that use only a tiny percent of the heating and cooling energy of conventional buildings. If the claims are true, meeting or exceeding E.U. PassivHaus standards just became routine.
RoofKrete is currently only available in the U.K., but they are looking for a U.S. licensee. I hope they find one. My gut feeling is that they have a good product that does what they say, but from this distance I can’t be sure. I strongly suspect it would be worth someone’s while to find out.