ThermalSheet Insulating Underlayment Support

No, for the installation of an Environ heating system with a floating floor like laminate, it is not necessary to adhere the ThermalSheet underlayment to the subfloor. The underlayment should instead be allowed to float freely on the subfloor. Make sure to stagger adjacent sheets of underlayment and tape them together to prevent any overlaps, ensuring a flat and even layer beneath your flooring. This method helps accommodate the natural expansion and contraction of the floating floor.

Yes, unlike natural cork, ThermalSheet will not expand from self leveling cement (SLC).

ThermalSheet Insulating Underlayment is a synthetic cork, a lightweight thermal barrier made of hemi-crystalline thermoplastic.

WarmlyYours recommends ThermalSheet underlayment when installing a floor heating system over a concrete slab to prevent heat loss and protect against moisture. It will not rot, support mold and mildew, or absorb moisture.

- ThermalSheet synthetic cork underlayment (6mm) has a 1.5 R-value, crack isolation up to 1/4“, reduces sound by up to 22 dB, and is Robinson tested (TCNA) and rated for residential loads.

- Cork (6mm) has a .72 R-value, crack isolation up to 1/32“, reduces sound by up to 23 dB, and is Robinson tested (TCNA) and rated for residential loads.

Yes. The floor never free-runs — the thermostat’s floor sensor governs output, and you set a maximum floor temperature limit in the thermostat itself. Most heated tile bathroom floors are set between 80°F and 85°F. Set that limit during commissioning and record it on the handoff sheet so the homeowner does not raise it past the flooring manufacturer’s rated maximum.

No. Put a skim coat of SLC (Self-Leveling Cement), or even plywood over it first. Then, the vinyl flooring product can be installed.

Yes, but the tear-out is the real risk. Scan the floor with thermal imaging before demo to map the existing hydronic tubing, and never fasten or drill into it. Keep the two systems on fully independent controls so they cannot fight each other, and do not place the electric floor sensor directly above a hydronic loop — the false-high reading will short-cycle the electric system. Call PRO technical support at 800-875-5285 to review the assembly before ordering.

No. Electric floor heating cable is listed for installation under floor coverings only, and NEC 424.38(A) does not permit heating cable to be installed in walls. Running it vertically voids both the UL listing and the warranty. For warm towels and a little extra room heat, specify a heated towel rack, which is designed and listed for wall mounting.

Yes, all pressure-sensitive adhesives are fine.

Yes, ThermalSheet should be bonded to the subfloor with any high quality modified thin-set, or with a bond coat adhesive. Further installation information can be found in the installation manual. 

No separate GFCI breaker is required — every WarmlyYours thermostat has a built-in Class A (5mA) GFCI. Stacking a GFCI breaker on top of it is one of the most common causes of nuisance tripping. Run a dedicated breaker sized to the load at 80% continuous duty: a 15A circuit carries up to 1,440W at 120V, a 20A circuit up to 1,920W. Loads beyond the thermostat’s 15A rating need a power module or relay.