Use the heating product’s approved floor assembly and the actual carpet and pad specifications.
A carpet pad’s location matters. Insulation below a heating element reduces heat loss downward; insulation above it resists heat reaching the carpet surface. Do not select a pad by a general high-R or low-R rule without checking the complete assembly.
- Environ Flex under carpet, USA only: the roll sits on the cushion and directly under the carpet. The manual recommends high-R underlayment over concrete and gives 6–8 lb/ft³ padding density in Compatible Underlayments. The carpet above the roll must be ¼–1 inch thick with R-value no greater than 1; rubber- or foam-backed carpet is excluded.
- Embedded TempZone Ruler Cable: the floor-covering materials above the heating system must not exceed the manual’s R-value limit of 1. Include the proposed overlying carpet/pad assembly when checking the system’s thermal limit. Do not apply the Environ cushion arrangement to an embedded cable installation.
Get the actual carpet and pad R-values from their manufacturers. Generic values based only on material name or thickness are estimates, not product approvals. Keep the flooring manufacturer’s temperature limits and use the specified floor sensor and installation assembly.
Sources: Environ Flex manual (pages 5 and 9) and TempZone Ruler Cable manual (Selection of Floor Covering Material).