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?

Exterior slab-edge insulation (retrofit)

Passive

One of 4 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.

What your site needs

Room to dig around the perimeter, and ground that can be opened without undermining the foundation or cutting buried services

The same cold path closed from outside on a house already standing. The perimeter is excavated to expose the slab edge, rigid insulation that does not mind moisture is fixed against it, and whatever is left above ground is capped and covered. Heavy work, but it does not need the house rebuilt.

Cost

Medium

Upkeep

Occasional

Skill to build

Intermediate

Lifespan

As long as the insulation itself; the above-grade cover protecting it from sun and impact is the part that gets renewed

Embodied carbon

Medium

Space / material use

Low

Output timing

None

Skill to repair

Basic

Inputs

none

Outputs

• Reduced heat loss

Compare the 4 ways to meet this need

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

• Exterior slab-edge insulation (retrofit) (This page)
  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: Yes
  Choose it if your house already stands on a slab and you want its cold floor edges put right.
• Continuous exterior insulation detailing
  Can I use it? Works in a flat · No rebuilding needed
  What does it cost me? Upfront cost: Medium · Skill to build: Basic · Upkeep: None · Change to daily life: None · Works without the grid: Yes
  Choose it if you want every beam and post covered, leaving no cold spot anywhere on the house.
• Strapped straw external insulation (ITE paille sanglee)
  Can I use it? Works in a flat · No rebuilding needed
  What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: Yes
  Choose it if you want to wrap an old house in thick insulation cheaply, without touching the rooms.
• Insulated slab edge and slab-to-wall thermal break
  Can I use it? Not in a flat · New build only
  What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: None · Change to daily life: None · Works without the grid: Yes
  Choose it if you are pouring a new slab and want warm floors at the edges from the start.

Sources

• Building America Solution Center, "Exterior Edge Insulation for Existing Foundation Slabs" (PNNL / US DOE): excavate to expose the slab edge, fix rigid non-moisture-sensitive insulation, protect the portion left above grade

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.