The maximum thickness of the flooring should not exceed 5/8” (15mm). The type and thickness of the flooring used with Environ Heating System must not exceed a thermal insulation “R” value of 1.
Underlayment can still be used but there ar some other factors to keep in mind. Bamboo flooring typically has a higher thermal resistance than tile, so the heating performance may be slightly diminished. Wood, bamboo, linoleum, cork and carpet all have different R-values (from 1 to 3) and they typically use an underlayment or a pad with an R-value of 1 to 2. The question naturally arises whether the radiant heat can effectively heat through all of that. Radiant heat transfers energy depending upon the density, humidity, and thermal resistance of the object. Ideally, the lower the R-value in the floor and underlayment, the better. Some underlayments, made from synthetic rubber, have extremely low R-values and are ideal for radiant heated floors because they allow the heat to transfer through more quickly.