Using HEAT-SHEET for Radon Mitigation

Radon is the second leading cause of lung cancer, created by the natural decay of uranium, which is found in almost all soils. It enters your house through cracks and other holes in your foundation.

Homes and buildings can trap radon inside, and the tighter a home is, the more radon can get trapped in it. Building codes have considered this and require Radon Mitigation for all new foundations.

In Minnesota, since 2009, all new homes are required to be built radon-resistant. Home builders must use material and techniques to help prevent radon from entering the home. This includes sealing radon entry points and installing a vent pipe, but it does not include a fan. Instead, this passive radon system relies on the natural upward flow of air to exhaust radon through the pipe. Learn More here:

HEAT-SHEET and Radon Mitigation

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. 

To use heat-sheet for radon mitigation, you will use the first layer nodels down, then apply a vapor barrier, followed by another layer of heat sheet in which you put your pex pipes.

If your home/shop is already built and your radon detector detects high enough levels you can get a radon mitigation system installed: See an example here: .