Radiant Heat Underlayment

Cork is a porous material, and it can absorb water if it gets wet. However, the extent to which cork absorbs water depends on various factors such as the type of cork, the density of the cork, the finish applied to it, and the amount of time it is exposed to water. Because of these facts, cork underlayment is not recommended when using self-leveling underlayment.

When installing electric floor heating over a concrete slab, an insulating underlayment like ThermalSheet is highly recommended to ensure efficient operation, faster heating times and warmer floor temperatures.

When WarmlyYours electric floor heating systems are being installed on a concrete slab, we strongly recommend adding a layer of insulation over the slab prior to installing the system. While our electric floor heating provides up to 25% more heating power per square foot than many of our competitors, the slab will always act as a "heat sink." Some of the heat that would otherwise be transferred to the flooring surface will remain in the slab, causing the floor’s surface temperature to be considerably lower. This is true with any electric radiant floor heating system.

When installed on top of a concrete slab without insulation, it is generally accepted that electric floor heating will take the chill away from the floor and provide a small amount of warmth. Adding insulation on top of the slab and beneath any electric radiant floor heating system will allow a greater percentage of the heat generated to transfer to the flooring surface. This results in greater efficiency and therefore faster warm up times, higher expected surface temperatures and lower energy usage. The floor will have the capacity to warm to a comfortable temperature, and in some cases can be employed as the primary heat source for that room.

The recommended types of insulation are natural cork, insulated tile backer boards and insulated underlayment, such as ThermalSheet™ synthetic cork.

The best way is to use our Radiant Floor Heating Quote Builder tool. It’s a great way to get an estimation by simply providing project information like room size and subfloor type. 

Reflective insulation is not effective with conductive heating, which is how embedded floor heating and snow-melting systems transfer heat. To be effective, the reflective insulation surface needs to face an air space (air gap), which allows the reflected heat to be redirected.

An effective solution considers the insulating material's R-Value. This is the rating of a material's insulating properties. The "R" stands for "resistance" and refers to the material's resistance to heat flow, or temperature conduction.

Installing Environ™ under wood laminate flooring requires a suitable underlayment beneath the heating elements. Never install Environ™ between two hard surfaces. Underlayments that are less than 2mm in thickness and that are not Robinson-rated are not acceptable. Underlayment is necessary to prevent Environ™ Flex Rolls from damage due to the weight of the floor, furniture, and people. Unavoidable wooden floor movements will not harm Environ™.

Installing Environ™ under carpeting(USA only) requires a suitable cushion/pad beneath the heating elements. Never install Environ™ between two hard surfaces. Carpet padding must have a density of at least 6 pounds per cubic foot, the higher the R-Value the better. 1/2“ Prime Urethane (R-2.15) and 1/2“ Bonded Urethane(R-2.1) are good choices. Adhere to Restrictions on Furniture Placement outlined on page 12 of Environ Install manual when installing under carpeting.

Environ™ must not be installed in direct contact with concrete, it is mandatory when installing over concrete to use a 1/4“ (6mm) Robinson-rated underlayment.

Certain underlayments, such as 1/4” (6mm) thick cork, or 6mm ThermalSheet are recommended for Environ™. It is also acceptable to place a vapor barrier, such as a plastic sheet, beneath the underlayment. Underlayment paper is not an acceptable underlayment choice.

Always check with the manufacturer of the flooring, carpeting, and underlayment for limitations and compatibility with electric radiant heating. Adhere to national and local code regarding electric radiant heating systems.

No, an uneven subfloor can cause tile lippage and stress the radiant heating cables, leading to cracks or system failure. Always level the subfloor using a self-leveling compound or patching material first. This creates a stable, flat surface that protects the heating elements and ensures a professional finish.

It’s highly recommended on concrete subfloors to prevent downward heat loss. Use ThermalSheet™ for best results.

Yes, we strongly recommend installing insulation like ThermalSheet™ over concrete slabs. Concrete acts as a "heat sink," absorbing warmth that should go to your floor. Insulation directs the heat upward, significantly improving efficiency, reducing warm-up times, and allowing the system to function effectively as a primary heat source.

It depends on your flooring type and heating system. For electric radiant floor heating, underlayment is often beneficial but not always required.When underlayment is recommended:

• Floating floors (laminate, engineered hardwood, LVP): Use ThermalSheet, WarmlyYours' insulating underlayment, to direct heat upward and improve efficiency.
• Cold subfloors (concrete, basements): Insulating underlayment prevents heat loss downward.

When underlayment is not needed:

• Tile and stone installations: Heating cables/mats are embedded directly in thinset or self-leveling compound—no underlayment required.
• Glue-down LVP over concrete: System can be installed in self-leveling compound without additional underlayment.

Important note: WarmlyYours currently offers ThermalSheet as our recommended underlayment solution. While CeraZorb and cork underlayment were previously available and may still be found in older installations, ThermalSheet is now our preferred product for optimal performance and compatibility.Our free SmartPlan service includes underlayment recommendations tailored to your specific flooring and subfloor. With over 600,000 custom floor plans created, we ensure you get the right system configuration.