The Difference Between a Radon Barrier and a Gas Permeable Layer (And How Our Engineered Insulation Products Help Achieve Both)

Logix Brands offer two engineered insulation products that help mitigate Radon ingress into homes and buildings: Halo Subterra Plus and Heat-Sheet Heavy.

However, the functions of these two products are vastly different. Subterra Plus is a superior radon barrier alternative to 6-mil poly, whereas Heat-Sheet Heavy is a more effective gas permeable layer than the industry-standard 4-inch granular layer.

In the post below, we describe the roles of both the radon barrier and the gas permeable layer, explain why Halo Subterra Plus and Heat-Sheet Heavy excel at these functions.

We will also present a regionally available “Cadillac Solution” for preventing under-slab Radon build-up and ingress into homes.

What Are the Code Provisions For Radon Mitigation?

With respect to radon, building codes look to block the path of the gas before it gets to the slab-on-grade, and then channel the gas to a point where it can be safely released into the atmosphere.

Generally, according to building codes in North America, this mitigation mechanism has three distinct components:

  • Radon barrier: This is the layer that actually blocks Radon’s ingress into a building.
  • Gas permeable layer: This element channels the gas toward a safe exhaust point.
  • Vent pipe: The pipe allows Radon to escape into the atmosphere without penetrating the building’s floors.

What Is a Radon Barrier?

A radon barrier is an air barrier, also known as a soil-gas retarder, that blocks the path of Radon immediately underneath the slab-on-grade.

A typical radon barrier is usually a layer of 6-mil poly; such a solution is code compliant and inexpensive, which is why builders tend to favor it.

However, testing done by the National Research Council (NRC) discovered that Halo’s Subterra Plus is 7 times more radon-resistant than 6-mil poly.

Halo Subterra Plus

A Sheet of Halo Subterra Plus

Using Halo Subterra Plus As a Radon Barrier

Halo’s Subterra Plus is an ultra-tough, high-performance under-slab insulation with a graphite polystyrene (GPS) foam core and cross-woven laminates on both sides of the foam core.

The laminate layers are what allow Subterra Plus boards to so effectively block Radon ingress (when properly taped). Thus, Subterra Plus is a compliant soil-gas retarded per IRC, Section AF103.3 and NBCC, Section

Opting for Subterra Plus instead of 6-mil poly gives your homes a seven-fold advantage in radon mitigation while also boosting the building’s thermal performance with R-5 per nominal inch. It’s a clear win-win.

However, it should be noted that Subterra Plus is a regionally available product that is made by Logix Brands members Beaver Plastics and AMC Foam. Subterra Plus is available in the western and central regions of Canada and the USA.

What Is a Gas Permeable Layer?

A gas permeable layer is a substrate placed beneath the radon barrier, which is designed to diffuse the Radon beneath the slab until it escapes through a dedicated vent pipe.

The code-compliant and widely accepted gas permeable layer is to use a 4-inch layer of clean granular material between the compacted (or undisturbed) soil and the soil-gas barrier.

Heat-Sheet Heavy Radon Mitigation Layer

Using Heat-Sheet Heavy as an Insulated Gas Permeable Layer

Logix Brands’ Heat-Sheet Heavy is a well-known solution for under-slab insulation and the efficient placement of PEX tubing for radiant heated slabs.

However, Heat-Sheet Heavy is a surprisingly effective gas permeable layer when installed with the “nodules down”.

Placing the Heat-Sheet Heavy panels with the nodules down creates a network of channels through which Radon can flow beneath the slab, eventually reaching its vent pipe.

These channels are wider and clearer than anything a granular layer can offer, and NRC testing shows that radon flow actually increases by about 50% when using Heat-Sheet Heavy instead of gravel.

Not only that, but Heat-Sheet Heavy is an effective insulator as well!

Heat-Sheet Heavy is a nationally available product and is available in all areas of Canada and the USA.

A Regionally Available “Cadillac Solution:” A combination of Subterra Plus and Heat-Sheet Heavy To Prevent Radon Ingress

A “Cadillac solution” for blocking Radon ingress is using both Halo Subterra Plus and Heat-Sheet Heavy.

In this configuration, Subterra Plus blocks the toxic gas, while the Heat-Sheet panels effectively channel Radon to the vent pipe.

Such a high-performance solution offers 7 times more resistance when blocking Radon, while being twice as effective at channeling the gas away from the slab than a granular layer.

This regionally available “Cadillac Solution” is available in the western and central regions of Canada and the USA only.

The Cadillac Solution - Heat-Sheet Heavy with Halo Subterra Plus

Wrapping It Up

Most typically used radon mitigation solutions fall far short of the effectiveness you can achieve using the Subterra Plus and Heat-Sheet Heavy combination.

Subterra Plus is a regionally available proven Radon barrier that’s seven times more effective than the industry-accepted 6-mil poly.

Meanwhile, Heat-Sheet Heavy is twice as effective at ensuring proper Radon flow to its venting point than the commonly used 4-inch granular layer.

You can use either of the two solutions to improve a home’s protection against Radon build-up and ingress.

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