Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?

Sealed slab and vapour barrier

Passive · New build only

One of 2 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.

A sealed floor slab laid over a tough plastic sheet that blocks gases rising from the ground. Radon and damp from the soil are stopped at the floor. It is simpler than extracting the gas with a sump, but less certain to keep it out.

Cost

Low

Upkeep

None

Skill to build

Basic

Lifespan

Vapour barrier membrane: 30-50+ years if undisturbed, similar failure mode to the airtight membrane

Embodied carbon

Low

Space / material use

Low

Output timing

None

Skill to repair

Basic

Regulation (FR example)

Radon risk information is compulsory for buildings in category-3 radon-potential communes. Mitigation is not itself permit-bound, but is expected where measured levels are high.

Inputs

none

Outputs

• Improved indoor air

Compare the 2 ways to meet this need

Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.

• Sealed slab and vapour barrier (This page)
  Can I use it? Not in a flat · New build only
  What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: None · Change to daily life: None · Works without the grid: Yes
  Choose it if you are pouring a new slab and want a simple barrier against soil gas and damp.
• Sub-slab depressurisation / radon sump
  Can I use it? Not in a flat · No rebuilding needed
  What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: No
  Choose it if radon is known in your area and you want it drawn away before it reaches the rooms.

Sources

• General vapour-barrier industry durability consensus

Limitations of this page

We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.