Am rebuilding circa 1944 cottage after a fire. In the rear section (700 sq ft) will be using sips for walls and roof. After much research and review have decided on electric radiant floor under ceramic tile. Since budget restraints have nixed the use concrete board it was decided to apply thinset/cables/tile directly to plywood subfloor per manufacturers recommendation. As this project has progressed our selection of materials and methods have increasingly taken us on the green path. With this in mind osb wins over plywood. My question is: will 3/4 osb serve as well as a base for the radiant floor? Should I be concerned with adhesion of thinset and is there any possibility of off gassing of the adhesive used in the osb itself? Product I'm looking at is called "Ainswoth Engineered" APA rated Sturd I Floor.  Structurally this stuff more than meets the need for a solid base on which to lay the 18" tile. Was wondering if anyone had encountered a dilemma such as this.  

look at this product: STEP Warmfloor www.warmfloor.com no thin set required.