If you read our last post, you already know radon is no joke. This invisible gas is the leading cause of lung cancer in non-smokers—and it’s surprisingly good at sneaking into homes through cracks, gaps, and foundation joints.
But here’s the good news: protecting your builds from radon doesn’t have to be complicated. In fact, it can actually make your job easier, save time, and boost the comfort and efficiency of the home. That’s where Heat-Sheet Heavy comes in.
First Off—What’s a Gas-Permeable Layer?
It’s a fancy name for a layer beneath the slab that lets soil gases (like radon) flow freely to a vent pipe, where they can be safely carried out of the building. Traditionally, builders use 4 inches of gravel under the slab for this.
Sounds simple enough, right?
Well, not so fast. Gravel can settle over time, and that airflow pathway? It can slowly disappear. And since homes today are built to last 75–100 years, relying on something that could lose performance as it ages isn’t ideal—especially when radon’s involved.
Why Heat-Sheet Heavy Changes the Game
Heat-Sheet Heavy is already a go-to for radiant floor heating—it’s durable, easy to work on, and those 1.25″ nodules lock in PEX tubing like a charm.
But flip it upside down, and you’ve got something even better: a high-performance radon diffusion layer.
Those same nodules form open channels beneath the slab, guiding radon gas toward your vent pipe. No gravel required. (But if your design includes gravel, it still plays nice.)
Even better? Heat-Sheet Heavy as a radon diffusion layer:
- Works for residential or commercial jobs
- Can be used with or without gravel
- Is compatible with clear poly or other air barriers like Subterra Plus.
“But Does It Work?” You Bet—And We Have the Testing to Prove It
We asked Canada’s National Research Council (NRC) to put Heat-Sheet Heavy to the test. They used their RIBETS lab (basically the gold standard for this kind of testing) to compare it head-to-head with a traditional 4″ gravel layer. (Click Here to read more about the testing.)
Here’s what they found:
- Gravel: 6.42 cfm airflow, -2.00 Pa pressure
- Heat-Sheet Heavy: 9.91 cfm airflow, -2.04 Pa pressure
That’s 50% better performance—with no risk of settling or shifting over time. Translation? Safer homes, simpler installs.
Radon Safe—With Real Jobsite Benefits
Using Heat-Sheet Heavy doesn’t just make your builds radon-ready. It also:
- Saves time—no need to trench and backfill gravel
- Cuts down on concrete over-pour
- Adds under-slab insulation for energy efficiency
- Delivers warmer floors your clients will feel every day
