Can the carbon system be used below 'real' wood floors or just laminate/engineered wood?

Yes. And it has been fitted below thousands of sqm of such real wood floors over the last few years. We have had no reported incidents of cracking, warping or other damage to the real wood floors. 3 points you should consider: 1. A 'floating' installation of the real wood floor is best (boards are glued/fixed together using the tongue & groove). 2. Carbon film secured onto battens at 400mm centre-centre spaces - please see our web page for details 3. Wood is a natural product and should be appropriately seasoned to ensure it is fully dried out before using for flooring. A good wood merchant should be able to advise on moisture content & suitability for use over underfloor heating.  more