Approved for use as a key component of under-slab radon gas mitigation systems for homes and buildings.

What is Radon and What Is The Risk?

Radon is the second leading cause of lung cancer.

Radon is created by the natural decay of uranium that is found is almost all soils. It’s a radioactive gas that moves up through the ground and can enter your home through cracks and other holes in your foundation.

Homes and buildings can trap radon inside and this risk will only increase as homes and buildings continue to be built more airtight over time.

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Heat-Sheet made with graphite polystyrene, placed "nodules-down" and used in an insulated under-slab radon mitigation insulation layer application.


Heat-Sheet® panels were originally designed to function as an under-slab foam board insulation with pre-molded nodules forming a grid pattern for pex piping to be “walked into place”, saving installers up to 75% of their pipe installation labor.

However, when installed with the ”nodules-down”, the interconnected channels created by Heat-Sheet® Heavy nodules’s nodules allow soil gas movement between the ground and the air barrier system to a venting pipe that can be connected to a radon mitigation system.

In fact, Heat-Sheet® Heavy has been tested per NRC’s Radon Infiltration Building Envelope Test System (RIBETS) to be able to serve, when placed with the nodules facing down, as an under slab gas permeable layer that is 50% more permeable than 4″ (0.1m) of clean granular material. Test results available upon request.

Benefits Of Using Heat-Sheet® Heavy As An Under-Slab Radon Mitigation Insulation Layer


Eliminates the need for the granular fill that is typically required as the gas permeable layer under slabs.


Provides under-slab insulation in a variety of thicknesses to satisfy a range of insulation values.


Supports the weight of cast-in-place concrete and foot traffic during construction.

Installation and Detailing Notes

An approved air and vapor barrier is required over Heat Sheet® Heavy to prevent radon gas ingress into the living space. This air/vapor barrier layer is typically a 6 mil polyethylene or an approved peel-and-stick membrane.

To provide a radon diffusion layer under a hydronically heated slab, you may install two layers of Heat-Sheet® with the layer of 6 mil polyethylene placed between them.